Inhibiting Pathogen Growth in Vivo with Anti-Microbial Agents

Antimicrobial Resistance

• An organism resistant to only one antimicrobial agent is termed a "single-drug resistant" organism.
• Some microorganisms exhibit resistance due to genetic mutations, enzymatic destruction of drugs, or changes in membrane permeability.
• Bacteria can acquire resistance to antibiotics through horizontal gene transfer, such as transformation, transduction, or conjugation.

Mechanisms of Resistance

• Chromosomal mutations can alter cell membrane structure, leading to decreased drug uptake, thus contributing to resistance.
• Acquired resistance involves previously susceptible bacteria developing resistance due to genetic changes.
• Superbugs refer to multidrug-resistant microorganisms, with certain fungi and viruses also classified as superbugs.

Antimicrobial Use and Effects

• Indiscriminate use of antimicrobial agents can lead to increased resistance, diminished effectiveness of drugs, and harm to beneficial microbiota.
• Severe allergic reactions to antimicrobial agents can manifest as anaphylaxis.
• Some antimicrobial agents, such as aminoglycosides, can cause auditory nerve damage, potentially leading to deafness.

Consequences of Antimicrobial Use

• Prolonged use of broad-spectrum antibiotics can result in superinfections and disruption of normal flora.
• Clindamycin is an example of an agent that can cause a superinfection due to significant alteration of indigenous microbiota.
• Chloramphenicol can lead to aplastic anemia, a serious and potentially fatal condition.

Antimicrobial Agents

• Antimicrobial agents target a wide range of pathogens while antibiotics specifically target bacterial infections.
• Semisynthetic antibiotics are chemically modified derivatives of naturally occurring antibiotics.
• Some antibiotics, like penicillin, are produced by moulds, specifically by fungi in the Penicillium genus.

Ideal Characteristics and Resistance Mechanisms

• The ideal antimicrobial agent is effective, safe, and has a low propensity to induce resistance.
• Resistance mechanisms include gene acquisition through plasmids and mobile genetic elements, enabling bacteria to obtain new genes.
• MDR (multidrug resistance) pumps are efflux mechanisms that expel a range of drugs from bacterial cells.

Inhibitors and Testing

• Beta-lactamases are enzymes produced by some bacteria that inactivate beta-lactam antibiotics, compromising their effectiveness.
• Notably, there are various types of beta-lactamases, with some being broader than others.
• Combining beta-lactam antibiotics with beta-lactamase inhibitors enhances their efficacy against resistant strains.

Clinical Considerations

• An antibiogram is a profile of antimicrobial susceptibility testing results for specific pathogens.
• Clinicians should avoid prescribing drugs to patients with known allergies to prevent severe reactions.
• Factors like age, immune status, and underlying health conditions must be considered when prescribing antimicrobial agents, especially for vulnerable populations.

Prescribing Guidelines

• When prescribing to hospitalized patients, factors such as therapy utility, antibiotic susceptibility, and potential drug interactions must be taken into account.
• For patients who are leukopenic or immunocompromised, a careful assessment of infection risk and appropriate prophylactic measures is critical.
• A balanced approach considering both efficacy and safety should guide the prescription of antimicrobial agents.

Learn about inhibiting the growth of pathogens in vivo using different anti-microbial agents. This quiz covers the definitions of antimicrobial agents, antibacterial agents, antifungal agents, and more as outlined by Algerico F. Baiño, Jr., RN in Chapter 9.