18. Antimicrobial Agents Flashcards
Name the 3 targets for antibiotics
Mnemonic ‘cant do prescribing’
C: cell wall synthesis
D- DNA synthesis
P: protein synthesis
Which antibiotic classes target cell wall synthesis? Give examples of each
Mnemonic ‘Bugger’
B: beta lactams - penicillins, cephalosporins, carbapenems
G: Glycopeptides - vancomycin
Which antibiotic classes target DNA synthesis?
Mnemonic: F$!Q
F: Folic acid antagonists - trimethoprim, sulphonamides
Q: Quinolones: Ciprofloxacin
Which antibiotic classes target protein synthesis?
Mnemonic: MAT
M: Macrolides e.g. erythromycin
A: Aminoglycosides: e.g. gentamicin
T: Tetracyclines e.g. tetracycline, lymecyclin
What are the 2 reasons we give antibiotics?
1) prevention of infection - this can be peri operative (1 dose), for short term e.g. meningitis household contacts, long term: asplenic and immunodeficient patients usually on for life and its usually a penicillin agent
2) treatment of significant infection -clinically significant means that an infection that left untreated will cause death , permanent harm or medium to long term disability.
- There may be treatment of culture proven infection
- or empirical treatment of suspected infection
What questions should we ask ourselves before prescribing?
What is the likely cause of infection? PMH, OH, TH, Age, time of year, background, site of infection, duration
Which antibiotic will be most effective? Severity, resistance, immune status,
Which one is best choice? Age, toxicity, safety, allergies, pregnancy, organ function, cost
What are breakpoints?
- tell us whether an antibiotic will be effective
- also takes into account MIC and antibiotic pharmacokinetics
- predicts likely response - susceptible, intermediate or resistant
What is meant by time dependent killing and concentration dependent killing?
Time dependent killing is the % of time free drug concentration excess MIC.
Concentration dependent killing is ratio of maximum drug concentration to MIC.
What are the 2 genetic basis of antibiotic resistance? Are there any other methods of antibiotics resistance?
1) chromosomal gene mutation
2) horizontal gene transfer
Other methods of antibiotics resistance:
- antibiotic inactivation
- alteration of target sites
- alteration of metabolic pathways
- reduced intracellular antibiotic accumulation
What is meant by MDR (multi drug resistance)?
- non susceptibility
- to at leats 1 agent
- in 3 or more antimicrobial categories
What is meant by extensively drug resistant?
- non susceptibility
- to at least 1 agent
- in all but 2 or fewer antimicrobial categories
What is meant by Pan drug resistant?
Non susceptibility
- to all agents
- in all antimicrobial categories
