Antimicrobial Use Flashcards
(23 cards)
What is the primary cause of antimicrobial resistance?
Antimicrobial use selects for resistant strains. Resistance genes existed naturally (e.g., β-lactam and tetracycline resistance genes found in 30,000-year-old bacteria DNA).
What is antimicrobial stewardship in small animal practice?
Rational prescribing, optimised therapy, and minimising unnecessary use to reduce resistance development and preserve antimicrobial effectiveness.
What is the recommended approach to prophylactic antimicrobials in surgery?
Not needed for all routine surgeries. Recommended in immunocompromised patients or surgeries >90 mins. Single preoperative dose can be as effective as postoperative course.
How are surgical wounds classified for antimicrobial use?
Clean: none needed (<90 min); Clean-contaminated: assess case-by-case; Contaminated/dirty: antimicrobials recommended due to high bacterial load.
Why is bacterial culture and sensitivity testing recommended?
To allow use of narrow-spectrum agents, avoid broad-spectrum use, reduce resistance pressure, and guide de-escalation.
Describe disk diffusion and MIC testing.
Disk diffusion (Kirby Bauer) classifies sensitive/resistant based on inhibition zone. MIC identifies the lowest drug concentration inhibiting bacterial growth (105 CFU/ml standard inoculum).
What factors influence antimicrobial penetration to infection sites?
Site of infection, blood supply, inflammation, solubility: beta-lactams are water-soluble (extracellular), fluoroquinolones and tetracyclines are lipid-soluble (intracellular).
What factors influence antimicrobial dosing strategies?
Concentration-dependent drugs (e.g., fluoroquinolones, metronidazole) require increased dose; time-dependent drugs (e.g., beta-lactams) benefit from increased dosing frequency.
What are the mechanisms of bacterial resistance?
Altered binding proteins, blocked antimicrobial affinity, drug-inactivating enzymes, reduced membrane permeability, membrane pumps removing drug.
What are the main genetic mechanisms of resistance transfer between bacteria?
Transformation (direct incorporation), conjugation (plasmid transfer), transduction (bacteriophage-mediated).
What is the mutant prevention concentration (MPC)?
Concentration required to prevent spontaneous resistant mutations (109 CFU testing). Drugs with a narrow mutant selection window (MSW), like pradofloxacin, reduce resistance risk.
Why is antimicrobial resistance testing important after therapy?
To confirm microbiological cure. Persistent bacteria after clinical cure indicate emerging resistance and risk of relapse.
What alternative therapies may help treat antimicrobial-resistant infections?
Topical disinfectants, manuka honey, silver dressings, surgical removal of infected tissue/implants, although evidence for pre- and probiotics is limited.
List the main mechanisms of antimicrobial action.
Targeting cell wall (penicillin, cephalosporins), bacterial DNA (fluoroquinolones), or ribosomal protein synthesis (aminoglycosides).
What are key properties of aminoglycosides?
e.g., Amikacin, Gentamicin. Protein synthesis inhibitors, gram-negative activity, poor oral absorption, nephrotoxicity, ototoxicity, bactericidal, concentration-dependent.
What are key properties of cephalosporins?
1st gen: gram+; 2nd gen: broader; 3rd gen: gram- incl. Pseudomonas. Bactericidal, time-dependent. Side effects: GI upset, hypersensitivity.
What are key properties of fluoroquinolones?
e.g., Enrofloxacin, Pradofloxacin. Inhibit DNA gyrase. Gram-negative coverage, lipid-soluble, bactericidal, concentration-dependent. Side effects: retinal degeneration (cats), cartilage damage in growing dogs.
Describe macrolides and lincosamides in veterinary medicine.
Macrolides (erythromycin), lincosamides (clindamycin). Bind 50S ribosome, gram+ and some anaerobe coverage. Lipophilic, bacteriostatic/bactericidal depending on concentration.
What are key properties of metronidazole?
Targets DNA under anaerobic conditions. Highly effective vs anaerobes, good tissue penetration incl. brain. Side effects: GI upset, rare CNS toxicity, teratogenicity.
What are key properties of penicillins?
Inhibit cell wall synthesis. Amoxicillin/clavulanate combats β-lactamase producers. Bactericidal, time-dependent, mostly urinary excretion. Hypersensitivity common side effect.
What are key properties of potentiated sulphonamides?
e.g., Trimethoprim/sulfadiazine. Inhibit folic acid synthesis. Broad spectrum incl. some protozoa. Side effects: KCS, hepatopathy, IMHA, cutaneous reactions.
Describe tetracyclines’ veterinary use and side effects.
e.g., Doxycycline. Protein synthesis inhibition (30S subunit). Broad spectrum incl. tick-borne pathogens. Side effects: GI upset, oesophagitis (cats), staining teeth, avoid in young/growing animals.
What are key recommendations for limiting antimicrobial resistance?
Use only when necessary, employ narrow-spectrum drugs, optimise dosing, use culture results to guide therapy, avoid cycling antimicrobials without culture confirmation.
