What are the main categories of antibiotics. How do antibiotics function in the body. Which factors influence antibiotic efficacy. What are the key pharmacokinetic and pharmacodynamic principles of antibiotics. How are antibiotics classified based on their effects on bacteria.

The Evolution and Significance of Antibiotics in Modern Medicine

Antibiotics have revolutionized modern healthcare, but their development has been a long journey from ancient times. Early attempts to treat infections involved unconventional methods such as using dyes, molds, and even heavy metals. Today, antibiotics are sophisticated compounds specifically designed to target bacteria, playing a crucial role in treating and preventing bacterial infections.

While various microorganisms, including viruses, fungi, and parasites, can cause infections, antibiotics are uniquely formulated to combat bacterial pathogens. This specificity is what makes them such powerful tools in the medical arsenal.

Understanding the Fundamental Mechanisms of Antibiotic Action

Antibiotics operate through two primary mechanisms:

1. Preventing bacterial cell reproduction
2. Altering essential cellular functions or processes within the bacterial cell

These mechanisms effectively disrupt the bacterial life cycle, either by stopping their multiplication or by directly causing cell death. The specific mode of action varies depending on the type of antibiotic and the target bacteria.

Bactericidal vs. Bacteriostatic: A Closer Look

Traditionally, antibiotics are classified into two main categories based on their effect on bacteria:

• Bactericidal antibiotics: Often described as those that “kill” bacteria
• Bacteriostatic antibiotics: Typically explained as those that “prevent growth” of bacteria

However, this simplistic categorization doesn’t capture the full complexity of antibiotic action. In reality, the distinction between bactericidal and bacteriostatic effects is more nuanced and depends on various factors.

Decoding the Science: Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC)

To accurately define the categories of antibiotics, we need to understand two key concepts:

• Minimum Inhibitory Concentration (MIC): The lowest concentration of an antibiotic that inhibits visible bacterial growth at 24 hours
• Minimum Bactericidal Concentration (MBC): The concentration of an antibiotic that reduces bacterial density by 1000-fold at 24 hours

The relationship between MBC and MIC helps determine whether an antibiotic is classified as bacteriostatic or bactericidal:

• Bacteriostatic activity: MBC to MIC ratio greater than 4
• Bactericidal activity: MBC to MIC ratio less than or equal to 4

This scientific approach provides a more accurate classification, though it’s important to note that these categories are not always mutually exclusive in real-world applications.

The Complex Reality of Antibiotic Efficacy in Clinical Practice

The effectiveness of antibiotics in treating infections is influenced by numerous factors, including:

• Pharmacokinetic principles
• Pharmacodynamic principles
• The specific bacteria being targeted
• The bacterial load in the infection
• The site of infection within the body

These factors can lead to some surprising outcomes. For instance, some antibiotics traditionally classified as bacteriostatic can exhibit bactericidal activity against certain bacteria. An example of this is linezolid, typically considered bacteriostatic, which can be bactericidal against Streptococcus pneumoniae.

Conversely, antibiotics classified as bactericidal may sometimes act in a bacteriostatic manner, depending on the specific bacterial strain and conditions. This flexibility in action highlights the importance of considering each clinical situation individually when selecting an antibiotic treatment.

Comprehensive Classification of Antimicrobial Agents

Antibiotics can be broadly categorized based on their primary mode of action:

Bacteriostatic Antibiotics

• Glycylcyclines (e.g., Tigecycline)
• Tetracyclines (e.g., Doxycycline, Minocycline)
• Lincosamides (e.g., Clindamycin)
• Macrolides (e.g., Azithromycin, Clarithromycin, Erythromycin)
• Oxazolidinones (e.g., Linezolid)
• Sulfonamides (e.g., Sulfamethoxazole)

Bactericidal Antibiotics

• Aminoglycosides (e.g., Tobramycin, Gentamicin, Amikacin)
• Beta-lactams (including penicillins, cephalosporins, carbapenems; e.g., Amoxicillin, Cefazolin, Meropenem)
• Fluoroquinolones (e.g., Ciprofloxacin, Levofloxacin, Moxifloxacin)
• Glycopeptides (e.g., Vancomycin)
• Cyclic Lipopeptides (e.g., Daptomycin)
• Nitroimidazoles (e.g., Metronidazole)

This classification provides a framework for understanding the diverse array of antibiotics available to clinicians. However, it’s crucial to remember that the actual behavior of these antibiotics can vary depending on the specific clinical context.

Unraveling the Complexities of Pharmacokinetics and Pharmacodynamics in Antibiotic Therapy

Optimizing antibiotic therapy requires a deep understanding of both pharmacokinetics (PK) and pharmacodynamics (PD). These principles work in tandem to determine the most effective dosing strategies for patients.

Pharmacokinetics: The Journey of Antibiotics in the Body

Pharmacokinetics describes how the body processes an antibiotic from the moment it enters until it’s eliminated. This process involves four main components:

1. Absorption
2. Distribution
3. Metabolism
4. Excretion

These factors collectively influence the concentration of the antibiotic in the body over time. Understanding PK helps clinicians predict how an antibiotic will behave in different patients and under various conditions.

Pharmacodynamics: The Impact of Antibiotics at the Infection Site

Pharmacodynamics focuses on the drug’s effect within the body once it reaches the target site of infection. Three main principles guide PD in antibiotic therapy:

1. The percentage of time the free drug concentration is above the MIC
2. The ratio of the area under the concentration curve to the MIC
3. The ratio of the maximum concentration to the MIC

These principles help determine the optimal dosing strategies for different antibiotics and infections.

Time-Dependent vs. Concentration-Dependent Killing

Antibiotics exhibit either time-dependent or concentration-dependent bactericidal activity:

• Concentration-dependent killing: Efficacy increases with higher antibiotic concentrations (e.g., fluoroquinolones, daptomycin)
• Time-dependent killing: Efficacy depends on the duration of effective antibiotic concentration (e.g., penicillins, tetracyclines)

Understanding these patterns is crucial for determining the most effective dosing regimens for different antibiotics.

Factors Influencing Antibiotic Distribution and Efficacy

Several factors affect how antibiotics distribute throughout the body and their ultimate effectiveness:

Volume of Distribution

The volume of distribution represents the ratio of the total amount of drug in the body to its serum concentration. This factor influences how widely an antibiotic spreads throughout the body’s tissues.

Protein Binding

The degree of protein binding affects the availability of the active drug at the infection site. Highly protein-bound antibiotics may have less free drug available for antimicrobial action, which can be particularly relevant in patients with conditions like hypoalbuminemia.

Lipophilicity

The lipophilicity of an antibiotic determines how well it can penetrate fatty tissues. In patients with increased adipose tissue, highly lipophilic antibiotics may have an increased volume of distribution.

Site of Infection

The location of the infection within the body is a critical consideration when selecting an antibiotic. Some antibiotics may be ineffective for certain types of infections due to poor penetration into specific tissues or body compartments.

Optimizing Antibiotic Therapy: Balancing Efficacy and Safety

Achieving optimal antibiotic therapy requires careful consideration of various factors:

• Patient-specific characteristics (age, weight, renal function, etc.)
• The specific pathogen and its susceptibility profile
• The site and severity of the infection
• Potential drug interactions and side effects

By integrating knowledge of antibiotic classifications, mechanisms of action, and PK/PD principles, clinicians can make informed decisions to maximize therapeutic efficacy while minimizing the risk of adverse effects and antibiotic resistance.

The Role of Therapeutic Drug Monitoring

For certain antibiotics, especially those with a narrow therapeutic index, therapeutic drug monitoring (TDM) can play a crucial role in optimizing therapy. TDM involves measuring drug concentrations in the blood at specific intervals to ensure that the antibiotic is maintained within its therapeutic range, balancing efficacy and toxicity.

Combination Therapy: When Two Is Better Than One

In some cases, combining multiple antibiotics may be necessary to achieve the desired therapeutic effect. Combination therapy can be beneficial in several scenarios:

• Broadening the spectrum of coverage for empiric therapy
• Treating polymicrobial infections
• Preventing the emergence of resistance
• Achieving synergistic effects against certain pathogens

However, combination therapy should be used judiciously to avoid unnecessary antibiotic exposure and potential antagonistic effects between drugs.

The Future of Antibiotic Therapy: Challenges and Innovations

As we look to the future of antibiotic therapy, several challenges and opportunities emerge:

Combating Antibiotic Resistance

The rise of antibiotic-resistant bacteria poses a significant threat to global health. Efforts to combat this challenge include:

• Development of new antibiotic classes
• Implementation of antibiotic stewardship programs
• Research into alternative antimicrobial strategies (e.g., bacteriophage therapy, immunomodulators)

Precision Medicine in Antibiotic Therapy

Advances in diagnostics and personalized medicine are opening new possibilities for tailoring antibiotic therapy to individual patients and pathogens. This approach may include:

• Rapid diagnostic tests for pathogen identification and susceptibility testing
• Pharmacogenomic testing to predict patient response to antibiotics
• AI-assisted decision support systems for antibiotic selection and dosing

Novel Drug Delivery Systems

Innovative drug delivery systems are being explored to enhance the efficacy of existing antibiotics and overcome resistance mechanisms. These may include:

• Nanoparticle-based delivery systems
• Targeted drug delivery to specific tissues or cell types
• Controlled-release formulations for optimized PK/PD profiles

As our understanding of antibiotics and bacterial pathogens continues to evolve, so too will our strategies for combating infectious diseases. The future of antibiotic therapy lies in the integration of advanced scientific knowledge, innovative technologies, and judicious clinical practice to provide optimal care for patients while preserving the effectiveness of these crucial medications for future generations.

Antibiotics – StatPearls – NCBI Bookshelf

Introduction

Antibiotics are common agents used in modern healthcare. This was not always the case. From ancient times, people sought ways to treat those with infections. Dyes, molds, and even heavy metals were thought to hold promise for healing.[1] Various microorganisms hold medical significance, including bacteria, viruses, fungi, and parasites. Antibiotics are compounds that target bacteria and, thus, are intended to treat and prevent bacterial infections.

Function

Classification

The pharmacology behind antibiotics includes destroying the bacterial cell by either preventing cell reproduction or changing a necessary cellular function or process within the cell. Antimicrobial agents are classically grouped into 2 main categories based on their in vitro effect on bacteria: bactericidal and bacteriostatic. Common teaching often explains that bactericidal antibiotics “kill” bacteria and bacteriostatic antibiotics “prevent growth” of bacteria. The true definition is not so simple. To accurately define each category, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) must be understood. The lowest concentration that inhibits visible bacterial growth at 24 hours is the MIC.[2] The MBC is the concentration of an antibiotic that reduces bacterial density by 1000-fold at 24 hours.[2] 

Bacteriostatic activity is further defined by an MBC to MIC ratio greater than 4; whereas, an MBC to MIC ratio less than or equal to 4 is bactericidal.[2] The clinical implications of antibiotic efficacy depend heavily on many factors not limited to: pharmacokinetic and pharmacodynamic principles, the particular bacteria, bacterial load, and site of infection. This is further complicated by the ability of some bacteriostatic antibiotics to exhibit bactericidal activity against particular bacteria.[3] Therefore, bacteriostatic antibiotics also kill bacteria, but the laboratory definition makes it seem as if they do not. For example, a bacteriostatic antibiotic such as linezolid can be bactericidal against Streptococcus pneumoniae.[3] This concept works in reverse, and bactericidal antimicrobials may also be bacteriostatic against certain bacterial strains and conditions. Conflicting data exist as to whether the necessity for bactericidal antibiotics is needed for severely ill or immunosuppressed patients.[3]

Types Antimicrobial Agents[3]  

Drug Class and Specific Antibiotics

Bacteriostatic

• Glycylcyclines: Tigecycline

• Tetracyclines: Doxycycline, minocycline

• Lincosamides: Clindamycin

• Macrolides: Azithromycin, clarithromycin, erythromycin

• Oxazolidinones: Linezolid

• Sulfonamides: Sulfamethoxazole

Bactericidal

• Aminoglycosides: Tobramycin, gentamicin, amikacin

• Beta-lactams (penicillins, cephalosporins, carbapenems): Amoxicillin, cefazolin, meropenem

• Fluoroquinolones: Ciprofloxacin, levofloxacin, moxifloxacin

• Glycopeptides: Vancomycin

• Cyclic Lipopeptides: Daptomycin

• Nitroimidazoles: Metronidazole

Pharmacokinetics and Pharmacodynamics

Pharmacokinetic (PK) and pharmacodynamic (PD) parameters are used together to maximize the efficacy of antimicrobial therapy through optimization of dosing in patients. Absorption, distribution, metabolism, and excretion are the PK components that affect the antibiotic concentration over time.[4] These processes describe how an antibiotic moves through the body from the time it enters the body until the parent drug or metabolites are removed. PD of an antibiotic describes the drug effect within the body when it reaches the infection target. The main principles that guide PD are the percent of the time the free drug is over the MIC, the amount of free drug area under the concentration to MIC, and maximum concentration to MIC.[5] Bactericidal activity is either concentration-dependent or time-dependent. If an antibiotic displays concentration-dependent killing, for example, fluoroquinolones or daptomycin, the efficacy of bacterial killing increases as the concentration of the antibiotic increases.[6] Penicillins and tetracyclines are time-dependent; therefore, the duration of the effective concentration of these antibiotics determines bactericidal activity. [6]

After an antibiotic is absorbed, the distribution influences the extent of antimicrobial activity. The total amount of drug in the body to serum concentration is the volume of distribution.[5] The level of protein binding will affect the availability of the active drug at the site of infection. If an antibiotic is highly protein-bound, there will be less free drug available for an antimicrobial effect, as seen in patients with hypoalbuminemia.[5] Increased adipose tissue in a patient will increase the volume of distribution if a drug has high lipophilicity properties.[7]

The location of infection is crucial to note because some antibiotics are inappropriate to treat certain infections. In the treatment of meningitis, for example, the penetration of the blood-brain barrier is critical if one wants to achieve therapeutic antibiotic levels at the site of infection to prevent treatment failure.[5]

Issues of Concern

Complications

Adverse Reactions

All medications have the potential for an adverse reaction, and antibiotics are no exception. One in five hospitalized patients has been shown to develop an adverse reaction to an antibiotic, and nearly the same proportion of drug-related Emergency Department visits are due to adverse antibiotic reactions.[8][9] An immune-mediated reaction or hypersensitivity is classified as an allergy.[10] This includes IgE-mediated anaphylaxis and angioedema. Medications often reach harmful levels in the body due to reduced metabolism and elimination, or high dosing regimens can cause toxicity due to supratherapeutic drug levels.[11] If a reaction occurs that is not mediated by the immune system and is unrelated to the drug level, then it is considered a side effect.[11]

The anticipation of adverse events is warranted when initiating antimicrobial therapy. Certain patients are at higher risk, for example, the elderly, patients with multiple co-morbidities, and hospitalized patients.[8] It is important to monitor patients for reactions as many develop over time. Some antibiotics necessitate monitoring of drug levels to guide therapy for efficacy and prevention of adverse effects such as vancomycin and aminoglycosides. [12] Renal toxicities may develop if these antimicrobials maintain high trough levels; therefore, monitoring renal function is necessary, in addition to measuring drug levels.

Adverse Reactions Associated with Organ Systems
[11]

Renal

Cardiac

Hematologic

Dermatologic

Neurologic

• Ototoxicity

• Vestibular dysfunction

• Seizure

• Peripheral neuropathy

Other

Antibiotic Resistance

The increased use of antimicrobial agents in clinical practice and other industries such as livestock farming has lead to bacterial resistance to antibiotic agents. Bacteria have developed mechanisms to promote this resistance in order to survive.  

The MIC of a bacterial isolate can serve as a metric for bacterial susceptibility to certain antibiotics.[13] A high MIC above the susceptibility threshold to an antibiotic will report as a resistant infection. Bacteria may possess resistance to an antimicrobial agent due to intrinsic or acquired properties. Not all antibiotics are effective against all types of bacteria. If a bacterium does not contain the target for a particular antibiotic, it is known to have intrinsic resistance.[14] Vancomycin, an antibiotic known to target work against gram-positive bacteria, cannot cross the cell wall of gram-negative bacteria.[15] Also, beta-lactam antibiotics require a cell wall to function and, therefore, will not be effective against bacteria such as Mycoplasma species that lack this cellular component.

Bacteria also have the capability to gain resistance through attaining resistance genes from other bacteria or developing a mutation resulting in reduced or elimination of antibiotic efficacy. This type of resistance is known as acquired resistance.[14]

More than one type of bacterial resistance may be present in a bacterial organism. Common resistance strategies are listed here.

Mechanisms of Resistance and Examples
[14]
[15]

Reducing Intracellular Antibiotic Concentrations

• Increased efflux

• Decreased influx

Antibiotic Inactivation

• Enzymatic modification

• Chemical degradation

Target Site Alteration

Clinical Significance

Approach to Antimicrobial Therapy

The causative organisms and infection source are not always known when a patient first presents.  Antibiotic therapy is often initiated before an exact infectious disease diagnosis is made and microbiological results are available. Antibiotics used in this manner are referred to as empiric therapy. This approach attempts to cover all potential pathogens. When microbiology tests result and antibiotic susceptibilities are known, definitive antibiotic therapy can then be tailored to the specific infection etiology.[16]

Prophylactic therapy is used to prevent infections in patients who do not have an active infection. Immunocompromised patients may receive prophylaxis against certain opportunistic pathogens. Prophylactic antibiotics are also used before surgical procedures and traumatic injuries such as open fractures and animal bites.[16]

The severity of potential bacterial infection will determine the level of aggressiveness in antibiotic therapy. For example, in a life-threatening infectious disease such as sepsis, empiric broad-spectrum parenteral antibiotics should be administered quickly after sepsis identification and continued until more information is gathered regarding the etiology and causative bacteria. [12] Empiric antibiotics are used to cover all potential bacteria before culture results. After bacterial cultures are available and have resulted, antibiotics can then be deescalated to only what is necessary. This approach is termed directed antibiotic therapy.[16] Often, empiric antibiotics are broad-spectrum, which refers to medications that target many different types of bacterial classes (i.e., gram-positive, gram-negative, and anaerobic bacteria). Whereas, in a simple skin and soft tissue infection that does not require hospitalization, narrower spectrum antibiotics may be given orally.[12]

In addition to the possible source(s) of infection, likely pathogens, and situation urgency, different patient factors merit consideration.[12] Patient age, medication allergies, renal and hepatic function, past medical history, the presence of an immunocompromised state, and recent antibiotic usage need to be evaluated before an antibiotic selection. Many of these patient factors contribute to the pharmacodynamics and pharmacokinetics of antibiotics that will influence dosing to optimize efficacy.

Enhancing Healthcare Team Outcomes

A Word on Antimicrobial Stewardship

In the United States, it has been reported that nearly half of the antibiotics prescribed were incorrect in some way, and almost one-third of antibiotics were deemed unnecessary in hospitalized patients.[17] Appropriate antibiotic use has become a public health issue (CDC 19). The practice of antimicrobial stewardship revolves around the concept of optimizing antimicrobial therapy and reducing adverse events through economically responsible methods.[18] These interprofessional programs work to identify ways to improve patient outcomes. Stewardship programs are increasingly becoming more common to address issues related to antibiotic usage, including combating antimicrobial resistance.

Antibiotic therapy and accompanying stewardship require the effort of an interprofessional healthcare team that includes clinicians, mid-level practitioners, pharmacists, and nursing staff. This includes only using these agents when clinically indicated, targeted therapy based on the susceptibility of the infectious organism, and monitoring of side effects and, where indicated, drug levels. Employing interprofessional strategies with open information sharing can improve therapeutic results with antibiotic therapy and minimize adverse events. [Level 5]

References

1.

Gould K. Antibiotics: from prehistory to the present day. J Antimicrob Chemother. 2016 Mar;71(3):572-5. [PubMed: 26851273]

2.

Pankey GA, Sabath LD. Clinical relevance of bacteriostatic versus bactericidal mechanisms of action in the treatment of Gram-positive bacterial infections. Clin Infect Dis. 2004 Mar 15;38(6):864-70. [PubMed: 14999632]

3.

Nemeth J, Oesch G, Kuster SP. Bacteriostatic versus bactericidal antibiotics for patients with serious bacterial infections: systematic review and meta-analysis. J Antimicrob Chemother. 2015 Feb;70(2):382-95. [PubMed: 25266070]

4.

Sy SK, Zhuang L, Derendorf H. Pharmacokinetics and pharmacodynamics in antibiotic dose optimization. Expert Opin Drug Metab Toxicol. 2016;12(1):93-114. [PubMed: 26652832]

5.

Onufrak NJ, Forrest A, Gonzalez D. Pharmacokinetic and Pharmacodynamic Principles of Anti-infective Dosing. Clin Ther. 2016 Sep;38(9):1930-47. [PMC free article: PMC5039113] [PubMed: 27449411]

6.

Ambrose PG, Bhavnani SM, Rubino CM, Louie A, Gumbo T, Forrest A, Drusano GL. Pharmacokinetics-pharmacodynamics of antimicrobial therapy: it’s not just for mice anymore. Clin Infect Dis. 2007 Jan 01;44(1):79-86. [PubMed: 17143821]

7.

Meng L, Mui E, Holubar MK, Deresinski SC. Comprehensive Guidance for Antibiotic Dosing in Obese Adults. Pharmacotherapy. 2017 Nov;37(11):1415-1431. [PubMed: 28869666]

8.

Tamma PD, Avdic E, Li DX, Dzintars K, Cosgrove SE. Association of Adverse Events With Antibiotic Use in Hospitalized Patients. JAMA Intern Med. 2017 Sep 01;177(9):1308-1315. [PMC free article: PMC5710569] [PubMed: 28604925]

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Shehab N, Patel PR, Srinivasan A, Budnitz DS. Emergency department visits for antibiotic-associated adverse events. Clin Infect Dis. 2008 Sep 15;47(6):735-43. [PubMed: 18694344]

10.

Gruchalla RS, Pirmohamed M. Clinical practice. Antibiotic allergy. N Engl J Med. 2006 Feb 09;354(6):601-9. [PubMed: 16467547]

11.

Granowitz EV, Brown RB. Antibiotic adverse reactions and drug interactions. Crit Care Clin. 2008 Apr;24(2):421-42, xi. [PubMed: 18361954]

12.

Lynch TJ. Choosing optimal antimicrobial therapies. Med Clin North Am. 2012 Nov;96(6):1079-94. [PubMed: 23102478]

13.

Brauner A, Fridman O, Gefen O, Balaban NQ. Distinguishing between resistance, tolerance and persistence to antibiotic treatment. Nat Rev Microbiol. 2016 Apr;14(5):320-30. [PubMed: 27080241]

14.

Chen LF, Chopra T, Kaye KS. Pathogens resistant to antibacterial agents. Infect Dis Clin North Am. 2009 Dec;23(4):817-45, vii. [PubMed: 19909886]

15.

van Duijkeren E, Schink AK, Roberts MC, Wang Y, Schwarz S. Mechanisms of Bacterial Resistance to Antimicrobial Agents. Microbiol Spectr. 2018 Jan;6(1) [PubMed: 29327680]

16.

Leekha S, Terrell CL, Edson RS. General principles of antimicrobial therapy. Mayo Clin Proc. 2011 Feb;86(2):156-67. [PMC free article: PMC3031442] [PubMed: 21282489]

17.

Fridkin S, Baggs J, Fagan R, Magill S, Pollack LA, Malpiedi P, Slayton R, Khader K, Rubin MA, Jones M, Samore MH, Dumyati G, Dodds-Ashley E, Meek J, Yousey-Hindes K, Jernigan J, Shehab N, Herrera R, McDonald CL, Schneider A, Srinivasan A., Centers for Disease Control and Prevention (CDC). Vital signs: improving antibiotic use among hospitalized patients. MMWR Morb Mortal Wkly Rep. 2014 Mar 07;63(9):194-200. [PMC free article: PMC4584728] [PubMed: 24598596]

18.

Cunha CB. Antimicrobial Stewardship Programs: Principles and Practice. Med Clin North Am. 2018 Sep;102(5):797-803. [PubMed: 30126571]

13.1E: Antibiotic Classifications – Biology LibreTexts

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1. Key Points
   1. Key Terms

Learning Objectives

Compare the two classes of antibiotics: bactericidal and bacteriostatic antibiotic

Antibiotics can be divided into two classes based on their mechanism of action. Bactericidal antibiotics kill bacteria; bacteriostatic antibiotics inhibit their growth or reproduction.

One way that bactericidal antibodies kill bacteria is by inhibiting cell wall synthesis. Examples include the Beta-lactam antibiotics (penicillin derivatives (penams) ), cephalosporins (cephems), monobactams, and carbapenems) and vancomycin. Other ways that bactericidal antibiotics kill bacteria include inhibiting bacterial enzymes or protein translation. Other batericidal agents include daptomycin, fluoroquinolones, metronidazole, nitrofurantoin, co-trimoxazole and telithromycin. Aminoglycosidic antibiotics are usually considered bactericidal, although they may be bacteriostatic with some organisms. The MBC (minimum bactericidal concentration) is the minimum concentration of drug which can kill 99.99% of the population.

Figure: Mechanism of penicillin inhibition: Penicillin and most other β-lactam antibiotics act by inhibiting penicillin-binding proteins, which normally catalyze cross-linking of bacterial cell walls.

Bacteriostatic antibiotics limit the growth of bacteria by interfering with bacterial protein production, DNA replication, or other aspects of bacterial cellular metabolism. This group includes: tetracyclines, sulfonamides, spectinomycin, trimethoprim, chloramphenicol, macrolides and lincosamides. They must work together with the immune system to remove the microorganisms from the body. However, there is not always a precise distinction between them and bactericidal antibiotics. High concentrations of some bacteriostatic agents are also bactericidal. The MIC (minimum inhibitory concentration) is the minimum concentration of drug which can inhibit the growth of the microorganism.

Figure: Structure of tetracycline: Tetracycline antibiotics are protein synthesis inhibitors, inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex. They do so mainly by binding to the 30S ribosomal subunit in the mRNA translation complex.

Further categorization is based on their target specificity. “Narrow-spectrum” antibacterial antibiotics target specific types of bacteria, such as Gram-negative or Gram-positive bacteria, whereas broad-spectrum antibiotics affect a wide range of bacteria, usually both gram positive and gram negative cells. Following a 40-year hiatus in discovering new classes of antibacterial compounds, three new classes of antibacterial antibiotics have been brought into clinical use: cyclic lipopeptides (such as daptomycin), glycylcyclines (such as tigecycline), and oxazolidinones (such as linezolid).

Key Points

• Bactericidal antibodies inhibit cell wall synthesis.
• Bacteriostatic antibiotics limit the growth of bacteria by interfering with bacterial protein production, DNA replication, or other aspects of bacterial cellular metabolism.
• Bacteriostatic antibiotics must work together with the immune system to remove the microorganisms from the body.

Key Terms

• bactericidal: An agent that kills bacteria.
• bacteriostatic: A drug that prevents bacterial growth and reproduction but does not necessarily kill them. When it is removed from the environment the bacteria start growing again.

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• Gram stain 01. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/File:Gram_stain_01.jpg. License: CC BY-SA: Attribution-ShareAlike
• Bactericidal. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Bactericidal. License: CC BY-SA: Attribution-ShareAlike
• Antibiotic Classification. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Antibio…tion%23Classes. License: CC BY-SA: Attribution-ShareAlike
• Pharmacology/Antibiotics. Provided by: Wikibooks. Located at: en.wikibooks.org/wiki/Pharmac…Bacteriostatic. License: CC BY-SA: Attribution-ShareAlike
• Bacteriostatic agent. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Bacteriostatic_agent. License: CC BY-SA: Attribution-ShareAlike
• bacteriostatic. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/bacteriostatic. License: CC BY-SA: Attribution-ShareAlike
• bactericidal. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/bactericidal. License: CC BY-SA: Attribution-ShareAlike
• Alexander Fleming. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/File:Al…er_Fleming.jpg. License: Public Domain: No Known Copyright
• Louis Pasteur. Provided by: Wikipedia. Located at: simple.Wikipedia.org/wiki/Fil…is_Pasteur.jpg. License: Public Domain: No Known Copyright
• Microbial cultures fridge. Provided by: Wikimedia. Located at: commons.wikimedia.org/wiki/File:Microbial_cultures_fridge.JPG. License: CC BY-SA: Attribution-ShareAlike
• Gram stain 01. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/File:Gram_stain_01.jpg. License: CC BY-SA: Attribution-ShareAlike
• File:Penicillin inhibition.svg – Wikipedia, the free encyclopedia. Provided by: Wikipedia. Located at: en.Wikipedia.org/w/index.php?…ion.svg&page=1. License: CC BY-SA: Attribution-ShareAlike
• Tetracyclines. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/File:Tetracyclines.png. License: CC BY-SA: Attribution-ShareAlike

Antibiotics – NHS

Antibiotics are used to treat or prevent some types of bacterial infection. They work by killing bacteria or preventing them from spreading. But they do not work for everything.

Many mild bacterial infections get better on their own without using antibiotics.

Antibiotics do not work for viral infections such as colds and flu, and most coughs and sore throats.

Antibiotics are no longer routinely used to treat:

• chest infections
• ear infections in children
• sore throats

When it comes to antibiotics, take your doctor’s advice on whether you need them or not. Antibiotic resistance is a big problem – taking antibiotics when you do not need them can mean they will not work for you in the future.

When antibiotics are needed

Antibiotics may be used to treat bacterial infections that:

• are unlikely to clear up without antibiotics
• could infect others
• could take too long to clear without treatment
• carry a risk of more serious complications

People at a high risk of infection may also be given antibiotics as a precaution, known as antibiotic prophylaxis.

Read more about when antibiotics are used and why they are not routinely used to treat infections.

How to take antibiotics?

Take antibiotics as directed on the packet or the patient information leaflet that comes with the medicine, or as instructed by your GP or pharmacist.

Antibiotics can come as:

• tablets, capsules or a liquid that you drink – these can be used to treat most types of mild to moderate infections in the body
• creams, lotions, sprays and drops – these are often used to treat skin infections and eye or ear infections
• injections – these can be given as an injection or through a drip directly into the blood or muscle, and are used for more serious infections

Missing a dose of antibiotics

If you forget to take a dose of your antibiotics, take that dose as soon as you remember and then continue to take your course of antibiotics as normal.

But if it’s almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Accidentally taking an extra dose

There’s an increased risk of side effects if you take 2 doses closer together than recommended.

Accidentally taking 1 extra dose of your antibiotic is unlikely to cause you any serious harm.

But it will increase your chances of getting side effects, such as pain in your stomach, diarrhoea, and feeling or being sick.

If you accidentally take more than 1 extra dose of your antibiotic, are worried or you get severe side effects, speak to your GP or call NHS 111 as soon as possible.

Side effects of antibiotics

As with any medicine, antibiotics can cause side effects. Most antibiotics do not cause problems if they’re used properly and serious side effects are rare.

The common side effects include:

• being sick
• feeling sick
• bloating and indigestion
• diarrhoea

Some people may have an allergic reaction to antibiotics, especially penicillin and a type called cephalosporins. In very rare cases, this can lead to a serious allergic reaction (anaphylaxis), which is a medical emergency.

Read more about the side effects of antibiotics.

Considerations and interactions

Some antibiotics are not suitable for people with certain medical problems, or women who are pregnant or breastfeeding. Only ever take antibiotics prescribed for you – never “borrow” them from a friend or family member.

Some antibiotics do not mix well with other medicines, such as the contraceptive pill and alcohol.

Read the information leaflet that comes with your medicine carefully and discuss any concerns with your pharmacist or GP.

Read more about:

Types of antibiotics

There are hundreds of different types of antibiotics, but most of them can be classified into 6 groups.

• Penicillins (such as penicillin, amoxicillin, co-amoxiclav, flucloxacillin and phenoxymethylpenicillin) – widely used to treat a variety of infections, including skin infections, chest infections and urinary tract infections
• Cephalosporins (such as cefalexin) – used to treat a wide range of infections, but some are also effective for treating more serious infections, such as septicaemia and meningitis
• Aminoglycosides (such as gentamicin and tobramycin) – tend to only be used in hospital to treat very serious illnesses such as septicaemia, as they can cause serious side effects, including hearing loss and kidney damage; they’re usually given by injection, but may be given as drops for some ear or eye infections
• Tetracyclines (such as tetracycline, doxycycline and lymecycline) – can be used to treat a wide range of infections, but are commonly used to treat acne and a skin condition called rosacea
• Macrolides (such as azithromycin, erythromycin and clarithromycin) – can be particularly useful for treating lung and chest infections, or as an alternative for people with a penicillin allergy, or to treat penicillin-resistant strains of bacteria
• Fluoroquinolones (such as ciprofloxacin and levofloxacin) – are broad-spectrum antibiotics that were once used to treat a wide range of infections, especially respiratory and urinary tract infections. These antibiotics are no longer used routinely because of the risk of serious side effects

Other antibiotics include chloramphenicol (used for eye and ear infections), fusidic acid (used for skin and eye infections), and nitrofurantoin and trimethoprim (used for urinary tract infections).

Page last reviewed: 23 May 2019
Next review due: 23 May 2022

Antibiotics | DermNet NZ

Author: Vanessa Ngan, Staff Writer. 2005.

What are antibiotics?

Antibiotics are chemical compounds used to kill or inhibit the growth of bacteria. Strictly speaking, antibiotics are a subgroup of organic anti-infective agents that are derived from bacteria or moulds that are toxic to other bacteria. However, the term antibiotic is now used loosely to include anti-infectives produced from synthetic and semisynthetic compounds.

The term antibiotic may be used interchangeably with the term antibacterial. However, it is incorrect to use the term antibiotic when referring to antiviral, antiprotozoal and antifungal agents.

History of antibiotics

Penicillin was the first antibiotic used successfully in treating bacterial infections. Sir Alexander Fleming first discovered it in 1928, but its potential for treatment against infections wasn’t recognised until over a decade later when Ernst B Chain, Sir Howard Florey and Norman Heatley produced enough purified penicillin to treat patients with. By the 1950s, a large number of antibiotics were being discovered and manufactured for the treatment of diseases caused by infecting bacteria. Over the last 50 years, antibiotics have transformed the patterns of disease and death.

Classification of antibiotics

Antibiotics can be classified in several ways. The most common method classifies them according to their chemical structure as antibiotics sharing the same or similar chemical structure will generally show similar patterns of antibacterial activity, effectiveness, toxicity and allergic potential.

B-lactam antibiotics inhibit bacterial cell wall synthesis. They include:

Penicillins

• Penicillin G
• Amoxicillin
• Flucloxacillin

Cephalosporins

• Cefoxitin
• Cefotaxime
• Ceftriaxone

Carbapenem

Macrolides inhibit bacterial protein synthesis.  

Tetracyclines inhibit bacterial protein synthesis.  

• Tetracycline
• Minocycline
• Doxycycline
• Lymecycline

Fluoroquinolones inhibit bacterial DNA synthesis. 

• Norfloxacin
• Ciprofloxacin
• Enoxacin
• Ofloxacin

Sulphonamides block bacterial cell metabolism by inhibiting enzymes. 

• Trimethoprim + sulphamethoxazole

Aminoglycosides inhibit bacterial protein synthesis. 

Imidazole antibiotics inhibit bacterial DNA synthesis.  

Peptides inhibit bacterial cell wall synthesis.  

Lincosamides inhibit bacterial protein synthesis.

The following drugs inhibit bacterial protein synthesis.

Uses of antibiotics

Antibiotics only work against infections caused by bacteria. Bacterial infections are much less common than viral infections. Most coughs and colds are of viral origin so antibiotics should not be prescribed for these. Antibiotics should only used when absolutely necessary, because:

• There is increasing resistance of bacteria to treatment
• Resistant bacteria are selected out by the use of antibiotics
• Antibiotics may have serious adverse effects in some people

Some common bacterial infections that do require antibiotic therapy include:

If these infections remain untreated, the resulting disease may be serious and even fatal.

In severe bacterial infections where patients may be hospitalized, often an intravenous broad-spectrum antibiotic (one that is active against many different bacteria) is given to start treatment. As soon as laboratory tests confirm the infecting bacteria, the antibiotic should be changed to one that is active against specific bacteria. After 48 hours of intravenous treatment, if there is clinical improvement, the patient may be switched to an oral form of the antibiotic.

Antibiotic resistance

The overuse and inappropriate use of antibiotics has led to antibiotic resistance. Bacteria that were once susceptible to antibiotics have developed ways to survive the drugs that were meant to kill or weaken them. This is also known as antibacterial resistance or drug resistance. Some diseases such as tuberculosis, gonorrhoea and childhood bacterial ear infections, that were once easily treated with antibiotics are now again becoming difficult to treat as bacteria have become resistant to these drugs. About 70% of bacteria that cause infections in hospitals are resistant to at least one of the antibiotics most commonly used to treat infections. Methicillin (meticillin) resistant Staphylococcus aureus (MRSA) is a particular problem for patients with skin diseases, ulcers and surgical wounds.

Doctor responsibility

• Only prescribe antibiotics if bacterial infection present
• Prescribe the approved dose and duration or as recommended by experts
• Educate patient about the importance of completing their course of antibiotics as instructed

Patient responsibility

• Understand that not all infections are bacterial and that not all bacterial infections will clear on antibiotics (eg, folliculitis)
• Take antibiotics exactly as instructed (ie, with or without food etc)
• Ensure you finish the course of antibiotics

Side effects of antibiotics

Antibiotics are associated with many side effects, including cutaneous adverse reactions. Some side effects are class-related but most reactions are specific to the agent in that individual.

Some common problems with antibiotics are listed below:

• Allergy to certain antibiotics or classes of antibiotics (eg, penicillin allergy)
• Many antibiotics cause gastrointestinal problems (eg, diarrhoea, vomiting, nausea)
• Antibiotics kill not only their targets but other useful micro-organisms that live in and on our body (flora) to prevent other diseases (eg, oral and/or vaginal thrush)
• A variety of skin rashes can occur, which may be mild (eg, hives) or devastating (eg, toxic epidermal necrolysis).

New Zealand approved datasheets are the official source of information for these prescription medicines, including approved uses and risk information. Check the individual New Zealand datasheet on the Medsafe website.

Antibiotics – Physiopedia

What are Antibiotics? Image R: Bacteria

• Any substance that inhibits the growth and replication of a bacterium or kills it outright.
• Designed to target bacterial infections within (or on) the body.^[1]
• Some are highly specialised and are only effective against certain bacteria. Others, known as broad-spectrum antibiotics, attack a wide range of bacteria, including ones that are beneficial to us.

Pharmacology of antibiotics: Includes destroying the bacterial cell by either preventing cell reproduction or changing a necessary cellular function (eg blocking an enzymes function) or process within the cell. Classically grouped into 2 main categories based on their in vitro effect on bacteria:

1. Bactericidal antibiotics “kill” bacteria – stop the mechanism responsible for building their cell walls^[1].
2. Bacteriostatic antibiotics “prevent growth” of bacteria – prevent the reproduction of bacteria.

• In the United States, it has been reported that nearly half of the antibiotics prescribed were incorrect in some way and almost one-third of antibiotics were deemed as unnecessary in hospitalized patients. Appropriate antibiotic use has become a public health issue^[2].

The first antibiotic, salvarsan, was deployed in 1910. In just over 100 years antibiotics have drastically changed modern medicine and extended the average human lifespan by 23 years. The discovery of penicillin in 1928 started the golden age of natural product antibiotic discovery that peaked in the mid-1950s. Since then, a gradual decline in antibiotic discovery and development and the evolution of drug resistance in many human pathogens has led to the current antimicrobial resistance crisis.^[3]

• Salvarsan provided the first real cure for the extremely unpleasant disease syphilis (caused by the parasitic spirochete Treponema pallidum)^[4].

Approach to Antimicrobial Therapy[edit | edit source]

Empiric Therapy[edit | edit source]

• The causative organisms and infection source are not always known when a patient first presents. Antibiotic therapy is often initiated before an exact infectious disease diagnosis is made and microbiological results are available. Antibiotics used in this manner are referred to as Empiric Therapy.
• Empiric antibiotics are broad-spectrum which refers to medications that target many different types of bacterial classes (i.e., gram-positive, gram-negative, and anaerobic bacteria).
• This approach attempts to cover all potential pathogens before culture results.
• When microbiology tests result and antibiotic susceptibilities are known, definitive antibiotic therapy can then be tailored to the specific infection etiology.

Prophylactic therapy[edit | edit source]

• Used to prevent infections in patients who do not have an active infection.
• Immunocompromised patients may receive prophylaxis against certain opportunistic pathogens.
• Prophylactic antibiotics are also used before surgical procedures and in traumatic injuries such as open fractures and animal bites.

Level of aggressiveness in antibiotic therapy[edit | edit source]

• The severity of potential bacterial infection will determine this. eg in a life-threatening infectious disease such as sepsis, empiric broad-spectrum parenteral antibiotics should be administered quickly after sepsis identification and continued until more information is gathered regarding the etiology and causative bacteria.

Patient factors (to be taken into consideration)[edit | edit source]

• Patient age, medication allergies, renal and hepatic function, past medical history, the presence of an immunocompromised state, and recent antibiotic usage need to be evaluated before an antibiotic selection. These patient factors contribute to the pharmacodynamics and pharmacokinetic actions of antibiotics and influence dosing to optimize efficacy.

i.e. A harmful or abnormal result. May be caused by administration of a medication and be indicated by an untoward result such as by illness or death

• One of 5 hospitalized patients has been shown to develop an adverse reaction to an antibiotic.
• Nearly the 1 out of 5 drug-related Emergency Department visits are due to adverse antibiotic reactions.
• Usually an immune-mediated reaction or hypersensitivity reaction (classified as an allergy). This includes IgE-mediated anaphylaxis and angioedema.
• The anticipation of adverse events is warranted when initiating antimicrobial therapy. Certain patients are at higher risk, for example, the elderly, patients with multiple co-morbidities, and hospitalized patients. ^[2]

i.e. An undesirable secondary effect which occurs in addition to the desired therapeutic effect of a drug or medication. Side effects may vary for each individual depending on the person’s disease state, age, weight, gender, ethnicity and general health.

1. Antibiotics commonly cause the following side effects:

• diarrhea
• nausea
• vomiting
• rash
• upset stomach
• fungal infections of the mouth, digestive tract, and vagina

2. Less common side effects of antibiotics include:

• formation of kidney stones, when taking sulphonamides
• abnormal blood clotting, when taking some cephalosporins
• sensitivity to sunlight, when taking tetracyclines
• blood disorders, when taking trimethoprim
• deafness, when taking erythromycin and the aminoglycosides
• Some people, especially older adults, may experience bowel inflammation, which can lead to severe, bloody diarrhea.
• In less common instances, penicillins, cephalosporins, and erythromycin can also cause inflamed bowels^[5].

Classification of Antibiotics[edit | edit source]

A broad range of antibiotics exist, each with its own sets of usage and action mechanisms.

• The most effective classification is derived from the chemical composition (antibiotics with similar structural classes typically have comparable patterns of toxicity, effectiveness and allergic potential).
• Even though each class consists of a variety of drugs, each one is still unique in its own way.

The main classifications are:

1. Beta-Lactam Antibiotics (Penicillin & Cephalosporin)[edit | edit source]

• Penicillin: The eldest type of antibiotics is penicillin. Generally bactericidal, penicillin hinders bacteria’s ability to form their cell walls. This antibiotic is often used in cases of dental, skin, respiratory tract, ear, and urinary tract infections as well as gonorrhea.
• Cephalosporin: In the same classification of antibiotics as penicillin even though its chemical structure differs in several respects. They both have a structure that hinders the growth of bacterial cell walls. The main difference is cephalosporin is cephalosporium acremonium based.

2. Fluoroquinolones[edit | edit source]

• The newest classification of antibiotics. A synthetic antibiotic, fluoroquinolones belong to the family of quinolones and are not derived from bacteria. These newer versions are broad-spectrum bacteriocidal antibiotics that are easily absorbed into the body. Because of this, fluoroquinolones can be administered in both pill form or intravenously. Fluoroquinolones work by inhibiting bacteria ability to produce DNA, making it difficult to reproduce.
• This antibiotic is mostly used to treat skin infections, urinary tract infection and respiratory infections like bronchitis and sinusitis.

3. Tetracycline[edit | edit source]

• Having a chemical structure with four rings, tetracyclines are derived from a type of Streptomyces bacteria. They are broad-spectrum bacteriostatic antibiotics, effective against a multitude of microorganisms.

4. Macrolides[edit | edit source]

• Obtained from the Streptomyces bacterium, macrolides are types of antibiotics that are bacteriostatic, thus inhibiting protein synthesis. The prototype of this class is erythromycin and is used similarly as penicillin.

5. Aminoglycosides[edit | edit source]

• Aminoglycosides are made from different Streptomyces species, which are derived from a fungus called Streptomyces griseus. They are bactericidal and stop bacteria from producing proteins^[6].

Bacteria can be divided into two groups on the basis of a process known as crystal violet staining, or Gram staining- these groups are known as gram-positive and gram-negative. Image: Gram stains with comparisons of gram positive and gram negative bacteria

1. Gram-positive bacteria have a thicker layer of peptidoglycan that makes up the cell wall and thus stain purple in a Gram stain test. Gram-negative bacteria have a cell wall composed of a thin layer of peptidoglycan surrounded by an outer membrane. This outer membrane of gram-negative bacteria contains a unique component, lipopolysaccharide, in addition to proteins and phospholipids.
2. The outer membrane of gram-negative bacteria is often hidden by a slime layer, which in turn hides the antigens of the cell. The unique structure of the outer membrane of gram-negative bacteria prevents certain drugs and antibiotics from entering into the cell, which means these bacteria have increased resistance to drugs and are more dangerous as disease-causing organisms^[7].

The increased use of antimicrobial agents in clinical practice and other industries such as livestock farming has lead to bacteria resistant to antibiotic agents.  Bacteria have developed mechanisms to promote this resistance in order to survive.

Bacteria also have the capability to gain resistance through attaining resistance genes from other bacteria or developing a mutation resulting in reduced or elimination of antibiotic efficacy. This type of resistance is known as acquired resistance

Antibiotics Coverage Diagram[edit | edit source]

Antibiotics: MedlinePlus

What are antibiotics?

Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply.

Antibiotics can be taken in different ways:

• Orally (by mouth). This could be pills, capsules, or liquids.
• Topically. This might be a cream, spray, or ointment that you put on your skin. It could also be eye ointment, eye drops, or ear drops.
• Through an injection or intravenously (I.V). This is usually for more serious infections.

What do antibiotics treat?

Antibiotics only treat certain bacterial infections, such as strep throat, urinary tract infections, and E. coli.

You may not need to take antibiotics for some bacterial infections. For example, you might not need them for many sinus infections or some ear infections. Taking antibiotics when they’re not needed won’t help you, and they can have side effects. Your health care provider can decide the best treatment for you when you’re sick. Don’t ask your provider to prescribe an antibiotic for you.

Do antibiotics treat viral infections?

Antibiotics do not work on viral infections. For example, you shouldn’t take antibiotics for

What are the side effects of antibiotics?

The side effects of antibiotics range from minor to very severe. Some of the common side effects include

More serious side effects can include

Call your health care provider if you develop any side effects while taking your antibiotic.

Why is it important to take antibiotics only when they’re needed?

You should only take antibiotics when they are needed because they can cause side effects and can contribute to antibiotic resistance. Antibiotic resistance happens when the bacteria change and become able to resist the effects of an antibiotic. This means that the bacteria continue to grow.

How do I use antibiotics correctly?

When you take antibiotics, it is important that you take them responsibly:

• Always follow the directions carefully. Finish your medicine even if you feel better. If you stop taking them too soon, some bacteria may survive and re-infect you.
• Don’t save your antibiotics for later
• Don’t share your antibiotic with others
• Don’t take antibiotics prescribed for someone else. This may delay the best treatment for you, make you even sicker, or cause side effects.

Centers for Disease Control and Prevention

Antibiotic Classification Table

Protein synthesis inhibitors

Major groups: aminoglycosides, tetracyclines, macrolides

General mechanism of action: Protein synthesis inhibiting antibiotics primarily target the bacterial ribosome (70S) which is made up of a small, 30S subunit and a large, 50S subunit. A ribosome is an essential, complex molecule made up of proteins and RNA and is responsible for synthesizing proteins. Aminoglycosides, macrolides, and other protein synthesis inhibitors target and prevent specific stages of protein synthesis at specific locations on 70S ribosomes. Bacterial death occurs because the cell cannot make proteins required for essential cellular processes.

Effects on humans – Humans, and other eukaryotic cells synthesize proteins using a 80S (not 70S) ribosome which is not targeted by these inhibitors. (other side effects are possible)

Click on any product below for more information.

Protein Synthesis Inhibitors

30S Subunit

50S Subunit

EF-G

Aminoglycosides

(initiation inhibitors)

Tetracycline antibiotics

(rRNA binding)

Peptidyl 

transferase

MLS 

(transpeptidation
/tranaslocation)

Steroid Antibacterials

-mycin

(Streptomyces)

-micin 

(Micromonospora)

Tetracyclines

Glycylcyclines

Amphenicols

Pleuromutilins

Macrolides

Lincosamides

Fusidic Acid

Nucleic acid synthesis inhibitors

Major groups: Antifolates, topoisomerase inhibitors (floroquinolones)

General mechanism of action: These antibiotics target different stages and pathways of nucleic acid (DNA, RNA…) synthesis. In summary, antifolates (includes sulfonamides) inhibit enzymes involved in folate/folic acid (vitamin B9) synthesis. Folate is an essential ingredient for the synthesis of pyrimidine and purines, two molecules found in nucleotides, the building blocks of DNA and other nucleic acids. Topoisomerase inhibitors prevent DNA replication by inhibiting topoisomerase activity. Toposiomerases are enzymes that relieve DNA supercoil stress during DNA replication. By inhibiting topoisomerase activity, DNA replication is greatly hindered and cell division rate is diminished.

Effects on humans – Humans acquire folate from dietary sources, they do not have a synthesis pathway for folate and are not affected by antifolates in the same way bacteria are. Topoisomerases can be found in human cells; however the molecular makeup of human topoisomerases differs from those found in bacteria. (other side effects are possible)

Click on any product below for more information.

Antifolates

Topoisomerase Inhibitors and quinolones

DHFR inhibitor

Sulfonamides

(DHPS inhibitor)

1 st generation

Fluoroquinolones

Short-acting

Intermediate

Long-acting

2nd generation

3rd generation

4th generation

Related(DG)

Anaerobic DNA
inhibitors

RNA synthesis

Nitro-imidazole derivatives

Nitrofuran derivatives

Rifamycins/RNA polymerase

Cell wall synthesis inhibitors

Major groups: Beta-lactams (cephalosporins, penicillins)

General mechanism of action: As the name implies, this group of antibiotics inhibits certain stages in bacterial cell wall synthesis. A major structural component in the bacterial cell wall (more so in Gram-positive bacteria) is an essential polymer called peptidoglycan. Beta-lactam antibiotics bind to PBPs or penicillin binding proteins which are involved in the final stages of peptidoglycan synthesis. By inhibiting PBP function, peptidoglycan cannot be properly synthesized and the cell lyses.

Effects on humans – Human cells do not use nor synthesize peptidoglycan and are therefore not susceptible to beta-lactam antibiotics. (other side effects are possible)

Click on any product below for more information.

Antibacterials:cell envelope antibiotics

Intracellular

Glycopeptide

B-lactams/ (inhibit PBP cross-links)

Penicillins

(penams)

β-lactamase sensitive

β-lactamase resistant

Penems

Carbapenems

Cephalosporins/

Cephamycins
(cephems)

Monobactams

β-lactamase

inhibitors

Combinations

1st

2nd

3rd

4th

Veterinary

90,000 Russia will tighten control over the use of antibiotics in the agro-industrial complex

17 August. FINMARKET.RU – The Russian government at a meeting on Tuesday supported a bill to tighten control over the use of antibiotics in agriculture.
This is a package of amendments to the laws “On Veterinary Medicine” and “On the Circulation of Medicines” prepared by the Rosselkhoznadzor. The bill introduces a ban on the addition of antimicrobial drugs to feed without a prescription, Deputy Prime Minister Victoria Abramchenko told reporters.The draft law will soon be sent to the State Duma.
“The amendments are aimed at strengthening control over the use of antibacterial drugs in livestock and poultry farming. According to expert estimates, uncontrolled use of antibiotics is one of the reasons for antibiotic resistance – the resistance of infectious agents to drugs. The bill introduces rules on prescription drugs, which will reduce the cases of their unjustified use and will improve the quality and safety of finished products, “Abramchenko said.According to the bill, it is proposed to establish a ban on the addition of antimicrobial drugs to feed and the sale of such feed in the absence of a requirement or a prescription. It is necessary to establish the categories of persons who need a pharmaceutical license to add antimicrobial drugs to feed during their production and sale. Registration of a prescription for a medicinal product for veterinary use will be possible in the federal state information system in the field of veterinary medicine.At the same time, the Rosselkhoznadzor is empowered to approve the list of medicines for veterinary use, including antimicrobial drugs dispensed by prescription or requirements, the form of requirements, the procedure for their registration, accounting and storage.
The entry into force of the federal law is envisaged from September 1, 2022.
According to the doctor of biological sciences, professor, head of the department “Biology and General Pathology” of the Don State Technical University Alexei Ermakov, according to WHO research, more than 70% of antibiotics produced in the world are used primarily in animal husbandry.”And it is not necessarily the veterinary services that do this, most often such drugs are used by farmers when feeding animals in order to increase profitability,” he said.
According to Budimir Plavsic, head of the regional office of the International Epizootic Bureau (OIE) for Europe in Moscow, “the unconscious use of feed with antibacterial drugs is a serious problem.” Control is paramount here, he stressed.

Antibiotics. Sources of antibiotics and history of appearance.How do antibiotics work? Are they harmful?

Antibiotics are drugs aimed at destroying living disease-causing bacteria; they entered our life more than half a century ago and firmly established themselves in it.

Thanks to antibiotics, diseases such as tuberculosis, pneumonia, gangrene and many other bacterial infections have ceased to be fatal to humans. But even the most potent antibacterial drugs are unable to cope with all pathogenic bacteria.This is due to the fact that pathogenic bacteria are constantly evolving, developing natural genetic mechanisms to resist drugs. The number of new generations of microbes “resistant” to even the most powerful antibiotics is growing inexorably every year. Scientists around the world are constantly looking for new effective methods to combat invulnerable bacteria.

History of antibiotics

Even in ancient times in China, India, Egypt and Greece, moldy bread and some types of plants were used to disinfect wounds and abscesses, mentions of the medicinal properties of mold were still in the works of ancient philosophers.In 1873, the scientific work of A.G. Polotebnov’s “The pathological significance of green mold” on the therapeutic effect of mold on purulent wounds, which he recommended to use it in the treatment of skin diseases. But this work did not receive due attention in medical circles. Bartomeleo Gosio, a physician and microbiologist, isolated mycophenolic acid from molds in 1896, the world’s first antibiotic that was active against the bacterium that causes anthrax. In 1987, the French military doctor Ernest Duchenne tested molds of the genus Penicillium on guinea pigs and found that the mold was damaging to the typhoid bacillus.Alas, his work also did not attract attention among the scientific community. Russian scientist M.G. Tartakovsky in 1904 stated that substances produced by green mold suppress the development of the pathogen of chicken cholera. American scientists Otis Fisher Black and Karl Alsberg in 1913 obtained a toxic substance from a mold of the genus Penicillium puberulum, which, as it later turned out to be penicillic acid, had antimicrobial properties. In 1928, the British bacteriologist Alexander Fleming carried out another work aimed at studying the protective reactions of the human body to infectious diseases provoked by staphylococcal bacteria.During the experiment in one of the laboratory dishes, Fleming discovered the formation of colonies of mold fungi, which got there in a completely random way. He noticed that there were no staphylococcal bacteria around the mold colonies. In the course of this experiment, the scientist concluded that the mold secretes a substance that destroys pathogenic bacteria and called it “penicillin”, since it was isolated from fungi of the genus Penicillium notatum, which he reported at a meeting of the Medical Research Club at the University of London on September 13, 1929 …But even then, Fleming’s work did not arouse much enthusiasm among doctors, since penicillin turned out to be an unstable substance that quickly collapsed even after short-term storage. Scientists German Ernst Boris Cheyne and Australian Howard Flory, who worked in England in the 30s of the twentieth century, came to grips with improving the effectiveness of penicillin. Soon they managed to get a sufficient amount of pure penicillin and test it on laboratory mice. This test showed a very high antibacterial efficacy of the drug.Due to the enormous mortality of soldiers from purulent wounds during the Second World War, the need for effective medicines was catastrophically great. In 1943, the mass production of penicillin began, thanks to this drug, hundreds of thousands of human lives were saved all over the world. And only in 1945 Howard Florey, Alexander Fleming and Ernst Boris Cheyne received the Nobel Prize in Medicine “For the discovery of penicillin and its healing effects in various infectious diseases.” Penicillin was followed by discoveries of other antibacterial agents.In the USSR, the first antibacterial medicine was “Krustozin”, the discovery of which belongs to the microbiologist Zinaida Ermolyeva in 1942. Until 2017, scientists around the world made various modifications of the drug, due to the emergence of bacterial resistance to existing drugs. In 2018, scientists from the University of Illinois developed a new class of semi-synthetic antibiotics. This drug was created on the basis of the dioxinibomycin compound and has shown its high efficiency against a wide range of gram-negative bacteria.Antibiotic in translation from Greek means “against life”. In 1942, this term was proposed by the American microbiologist Zelman Waxman, whose name is associated with the discovery of another antibacterial agent, streptomycin, which is still used today to treat tuberculosis.

Sources of antibiotics

The main sources of antibiotics are actinomycetes (produce about 80% of natural antibiotics), mold fungi and typical bacteria, but they are far from the only ones. Today science knows about 30,000 antibiotics of natural origin, but this does not mean at all that all antibiotics existing today are produced by living cells.Scientists chemists since the 60s have learned to significantly improve the antimicrobial properties of antibiotics produced by natural microorganisms, modifying them by chemical methods. The preparations obtained in this way are classified as semi-synthetic antibiotics. Of the whole variety of antibiotics, only about a hundred are used for medical purposes.

Methods for producing antibiotics

• Biological synthesis (cultivation of producers and their isolation of antibiotics in the course of their life)
• Boisynthesis with chemical modifications (semi-synthetic antibiotics)
• Chemical synthesis (synthetic analogs of natural antibiotics)

Classification of antibiotics

Depending on the nature of the effect of an antibacterial drug on a pathological cell, antibiotics are divided into two groups: bacteriostatic (pathogenic bacteria remain alive, but lose their ability to reproduce) and bactericidal (bacteria die and are removed from the body).Classification of antibiotics by chemical structure:

• Beta-lactams (penicillins, cephalosporins, carbapenems, monobactams)
• Glycopeptides (vancomycin, teicoplanin)
• Aminoglycosides (streptomycin, monomycin, kanamycin, t; neomycin – generations of genetics – 2nd generation)
• Tetracyclines
• Macrolides (and azalides)
• Lincosamides
• Levomycetin (chloramphenicol)
• Rifamycins
• Polypeptides
• Polyenes
• Various antibiotics (fusidfunic acid, fuza.)

Classification by direction of action:

• Antibacterial antibiotics (the most numerous group of drugs):
• active against gram-positive microorganisms;
• broad-spectrum – act simultaneously on gram-positive and gram-negative bacteria;
• anti-tuberculosis, anti-leprosy, anti-syphilitic drugs;
• Antifungal
• Antineoplastic antibiotics
• Antiprotozoal and antiviral antibiotics

How do antibiotics work?

The main task of an antibiotic, when it enters the body, is to attach to a bacterium in order to destroy it or prevent it from multiplying, as a result of which it will die on its own.To do this, each antibiotic has its own target, as a rule, it is a protein, enzyme or part of the DNA of a pathogenic microorganism, and the mechanism of action on the bacterium. That is why certain antibacterial drugs are prescribed, depending on the causative agent of the disease. In medical practice, drugs are used that strike targets without affecting the cells of our body.

Antibiotic treatment

You cannot prescribe antibiotics on your own, only a doctor can do such an appointment.Antibacterial drugs are used to prevent and treat inflammation caused by pathogenic bacteria. Treatment of viral diseases, for example, ARVI, will not be effective. You should not accompany antibiotic therapy with other drugs that can affect their action, and it is also important to observe an equal interval of time between doses of antimicrobial agents and in no case combine treatment with alcohol. Do not stop taking antibiotics if you feel relieved, and you must complete the full course of treatment prescribed by a qualified professional.If taking an antibiotic does not give a result within 72 hours from the start of treatment, you should contact your attending physician with a request to replace the prescribed drug.

Are antibiotics dangerous?

Like any medicine, antibiotics are not without side effects. The variety of drugs is great and each has its own characteristics. Some drugs are allowed for all age groups, others are strictly contraindicated for children under a certain age, pregnant women, it is important to know which drugs can be combined with each other and which are strictly prohibited.The most common, but far from the only side effects include:

• Nausea
• Diarrhea, constipation
• Abdominal pain
• Dizziness
• Allergic reactions

Butchers warned against the use of antibiotics for COVID-19 – RBK

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Photo: Anton Vaganov / Reuters

Doctor and TV presenter Alexander Myasnikov warned Russians about the dangers of hormonal drugs and antibiotics in the treatment of coronavirus infection on an outpatient basis.He published the corresponding statement on his Telegram channel.

The doctor recalled that the coronavirus belongs to the category of acute respiratory infections and, in treatment, requires only auxiliary means, and not the use of potent drugs (hormonal and antibiotics). “You cannot use at home for the treatment of acute respiratory infections what is used in hospitals to treat severe viral pneumonia! Side effects can even be fatal! ” – explained Myasnikov.

In the United States, named dangerous drugs in the treatment of COVID-19

Instead, he advised, as with viral acute respiratory infections, to eat lightly, drink plenty of fluids, and also take antipyretic drugs.He also suggested paying attention to vitamins, minerals and interferons in nose drops.

Earlier, Joshua Shaffzin, MD, head of infection control and prevention at the Children’s Hospital in Cincinnati, Ohio, recommended that antidiarrheal drugs with loperamide and inhalers be abandoned during treatment for COVID-19. The doctor explained that loperamide slows down the work of the intestines, which prevents the body from getting rid of bacteria on its own.

90,000 They want to tighten control over the use of antibiotics in veterinary medicine

© AGN Moscow

Russia may prohibit the addition of antimicrobial drugs to feed without a prescription.Such a bill is planned to be considered by the State Duma Committee on Agrarian Issues before the first reading in the chamber, according to the committee’s website.

A government bill prohibits the addition of antimicrobial drugs to feed without a requirement or prescription. In addition, it establishes the category of persons who require a pharmaceutical license to add antibiotics to feed. A prescription for a medicine for veterinary use can be obtained from the federal state information system in the field of veterinary medicine.

The authority to approve the list of medicines for veterinary use, including antimicrobial drugs, the procedure for their registration, accounting and storage is proposed to be vested in Rosselkhoznadzor. If the bill is passed, it will enter into force on September 1, 2022.

Let us remind you that earlier the Ministry of Agriculture drew up a list of drugs, the use of which they want to restrict in veterinary medicine. The list includes antibiotics, which are most often used to prevent various diseases in farm animals.Limit veterinarians to the use of certain medications for chickens, cows or pigs wanting to save lives. The fact is that antibiotics are not removed for a long time and, together with animal meat, can enter the human body. As a result, the body quickly gets used to such drugs and they cease to act on bacterial infections.

Also read about what laws go into effect in November.

90,000 Antibiotics for angina – diagnosis and causes

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Angina
Is an acute infectious disease in which the infection affects the palatine
tonsils.

Reasons for the development of angina

U
children over 5 years old in 90% of cases, angina is a bacterial infection. How
usually the causative agent is
beta-hemolytic streptococcus, and every fifth child has angina
staphylococcal or combined infection of staphylococcus with streptococcus. In babies under three years old, the nature of sore throat is more common.
viral – this can be:

• herpes viruses
• cytomegalovirus
• adenoviruses
• virus
  Epstein Barrra (causative agent of infectious mononucleosis)
• respiratory syncytial
  virus
• enterovirus.

Also
the cause of sore throat can be: fungi, pneumococci, spirochetes.

Ways
transmission of infection:

1. by airborne droplets
2. contact and household (through toys, dishes, food)

Onset
sore throats are promoted by the following factors:

1. hypothermia
2. cold
   drinks
3. overwork
4. irrational
   food
5. decline
   immunity
6. recently
   transferred viral infections.
7. decline
   immunity
8. Stock
   any focus of infection in the body (caries, sinusitis, otitis media)

What
there are varieties of sore throats:

1. Banal (catarrhal, follicular,
   mixed, phlegmonous)
2. Atypical (viral, fungal,
   ulcerative necrotic)

3. Sore throats developing with infectious
   diseases (measles, diphtheria, scarlet fever, syphilitic, with
   HIV infection)

4. Angina with blood diseases (agranulocytic,
   monocytic, leukocytic)

5. Sore throats, allocated by localization (tonsillitis
   larynx, tonsillitis of the pharyngeal tonsil, lingual, tubular, tonsillitis of the lateral
   rollers)

How
diagnose angina

1. Acute onset – an increase in body temperature up to
   39-40 *

2. Weakness, malaise, headache, apathy,
   lack of appetite, chills

3. Increase, redness of the tonsils, appearance
   pustules, difficulty swallowing.

Even
one of the listed symptoms is the reason for immediate referral to
to the doctor, since only a doctor should diagnose and treat angina.
Self-medication for angina is unacceptable, since the diagnosis and treatment is not so
simple as it seems at first glance. You can skip other illnesses that
symptoms are similar to angina. And not correct and not prescribed therapy on time can
lead to serious complications such as:

1. rheumatic lesion of the heart muscle, which
   very dangerous by the formation of valvular defects.

2. pyelonephritis, glomerulonephritis

3. joint damage

4. abscess,
   phlegmon of cellulose

5. laryngeal edema

Therefore
it is extremely important to diagnose the cause of sore throat in time.

Do I need to give antibiotics for angina?

Antibiotics
with angina should be given if angina is of bacterial origin, which
only a doctor can determine.With viral sore throat – antiviral
drugs, antibiotics will not help here. And the healing process can
drag on, and moreover lead to complications. With fungal sore throat –
antifungal drugs are needed, but antibiotics in this situation are not
only they will not help, but only aggravate the course of the disease.

For
high-quality treatment of angina requires timely correct diagnosis and
optimal selection of the drug. The capabilities of our clinic allow us to
diagnose the cause of sore throat, prescribe and carry out the optimal
treatment, preventing complications.Carry out comprehensive prevention in time.

Call
right now! The clinic works around the clock!

Absorbent material from PET bottles to remove antibiotics from water

The Korea Institute of Science and Technology announced that a group of scientists from the KIST Water Cycle Research Center has developed a highly efficient adsorbent material using PET bottles.

South Korea with high levels of antibiotic use is classified as a country with a high risk of multidrug-resistant bacteria, or so-called “super bacteria”.According to the Ministry of the Environment, antibiotic substances have been found in sewage treatment plants and in rivers.
The Korea Institute of Science and Technology announced that a research team led by researchers Jung Kyung-won and Choi Jae-woo of the KIST Water Cycle Research Center has developed a highly efficient adsorbent material using PET bottles. The new material is expected to help address environmental toxins and antibiotic-resistant bacteria caused by antibiotic spills into water.
Currently, the most well-known method for effectively removing antibiotics from water is the use of a porous carbon composite synthesized by pyrolysis of organometallic frameworks (MOF). Porous carbon composites adsorb antibiotics in water, thereby removing them. However, since the organic ligand commonly used to synthesize MOF is very expensive, cost is a major obstacle to the widespread practical application of this method through mass production.
To develop a more cost-effective solution, the KIST research team focused on the PET bottles that people use in their daily lives. PET is a high molecular weight compound obtained from the polymerization of ethylene glycol and terephthalic acid, the latter of which is used as an organic ligand for the synthesis of MOF. The KIST research team extracted a high-purity organic ligand from PET bottles and used it to synthesize a highly efficient adsorbent material that could effectively remove antibiotics from water in an environmentally and cost-effective way.

More details: https://econet.by/articles/adsorbiruyuschiy-material-iz-pet-butylok-dlya-udaleniya-antibiotikov-iz-vody

Modern approaches to the diagnosis and treatment of COPD

Consider general principles of treatment exacerbation chronic bronchitis:
– Bed rest
– Detoxification therapy
– Antibacterial therapy (optimally early – no later than 8 hours after the onset of clinical manifestations)
– Symptomatic therapy (expectorant drugs, bronchodilators)
– Correction of impaired functions of the respiratory system and others systems of the body (expansion of basic therapy)
– Correction of the treatment of diseases that contribute to the development of pneumonia (immunomodulators, etc.)etc.).

With regard to antibiotic therapy, 4 main groups of antibiotics are used in this situation: protected beta-lactam antibiotics, macrolides or tetracyclines, respiratory fluoroquinolones, and third and fourth generation cephalosporins.

The main disadvantage of all beta-lactam antibiotics is the lack of activity against “atypical” microorganisms (Legionella spp.).

Macrolides should be preferred if an “atypical” etiology is suspected (M.pneumoniae, S. pneumoniae, Legionella spp.). The advantage of macrolides is also good penetration into bronchial secretions and lung tissue, a favorable safety profile and the absence of cross-allergy to beta-lactam antibiotics).

Fluoroquinolones possess a wide spectrum of antibacterial activity, there is a possibility of stepwise therapy, and have a long half-life.

I generation of fluoroquinolones : nalidixic acid, pipemidic acid.