S9) Antimicrobial Agents Flashcards
What is an antibacterial drug?
An antibacterial drug is a chemical substance that kills or inhibits the growth of bacteria at a discrete target site
What is an antibiotic?
An antibiotic is an antibacterial drug of microbial origin e.g. penicillin from Penicillium mold
What is the unique property of antimicrobials?
Antimicrobials target microbial biochemistry
Identify some antibiotics which target DNA synthesis
- Quinolones e.g. ciprofloxacin
- Folic acid antagonists e.g. trimethoprim sulphonamides
Identify some antibiotics which target protein synthesis
- Aminoglycosides e.g. gentamicin
- Macrolides e.g. erythromicin
- Tetracyclines
Identify some antibiotics which target cell wall synthesis
- Beta-lactams e.g. penicillins, cephalosporins, carbapenems
- Glycopeptides e.g. vancomycin
What are the two reasons for antibiotics?
- Prevention of infections
- Therapy of significant bacterial infections
Identify some groups of people at increased risk of infection
- Peri-operative – prevention of surgical site infections
- Short term – meningitis contacts
- Long term – asplenia, immunodeficiency
What are clinically significant infections?
Clinically significant infections are infections that if left untreated will cause death, permanent harm or medium to long term disability
What are the two ways in which one can treat a clinically significant infection?
- Treatment of culture-proven infection
- Empirical treatment of suspected infection
What are the two different ways that one might use antibiotics empirically?
Which factors helps one determine the likely cause of an infection?
Which factors helps one determine which antibiotics are likely to be effective?
Which factors helps one determine which antibiotic is the best choice?
What are the adverse events of antibiotics?
- Toxicities
- Allergic reactions
- Idiosyncratic reactions
- Ecological effects – C.difficile, selection of resistance
- Drug interactions
What would ideal antibiotic therapy look like?
- Clean kill of infecting bacteria – minimal impact on commensal organisms, no resistance in any surviving pathogens
- No unwanted effects in patient e.g. drug interactions, toxicities
Illustrate how one measures the susceptibility of bacteria to antibacterials
What is the minimum inhibitory concentration?
MIC is the minimum concentration of antibiotic required to inhibit growth of a bacterium in vitro (mg/l)
Therapeutic drug monitoring is used to ensure a non-toxic adequate dose for some antibiotics.
Identify these
- Aminoglycosides
- Glycopeptides
Describe the mechanism of antibiotic resistance through the following pathways:
- Antibiotic inactivation
- Alteration of target site
- Alteration of metabolic pathways
- Reduced intracellular antibiotic accumulation
What does it mean when a pathogen is multi-drug resistant?
Multi-drug resistant – non-susceptibility to at least one agent in three or more antimicrobial categories
What does it mean when a pathogen is extensively drug resistant?
Extensively drug resistant – on-susceptibility to at least one agent in all but two or fewer antimicrobial categories
What does it mean when a pathogen is pan drug resistant?
Pan drug resistant – non-susceptibility to all agents in al antimicrobial categories
Identify the two ways in which bacteria can become resistant to carbapenem
- Reduced bacterial intracellular concentration
- Carbapenemase production
