Antimicrobial agents Flashcards
Which antibiotics cannot be used in penicillin allergic patients due to cross-sensitivity?
Penicillins, cephalosporins and carbapenams have cross-reactivity in up to 10% of penicillin allergic patients.
Which of the following could be used in a severely penicillin allergic patient?
(piperacillin, teicoplanin, cefradine, clarithromycin, imipenem)
Piperacillin - NO penicillin
Cefradine - NO cephalosporin
Imepenem - NO carbapenem
Teicoplanin - YES glycopeptide
Clarithromycin - YES macrolide
Which of the following have anaerobic cover?
(imipenem, metronidazole, trimethoprim, aztreonam, vancomycin)
Imipenem - wide spectrum including some anaerobes
Metronidazole - only covers anaerobes and parasites
What is aztreonam?
Aztreonam is a monobactam with no useful activity against anaerobes or gram-positive organisms; it covers a wide range of gram-negative bacteria.
What are the bacteriocidal antibiotics?
Penicillins, cephalosporins, carbapenems, aminoglycosides, quinolones, metronidazole, vancomycin.
What are the bacteriostatic antibiotics?
Sulphonamides, tetracyclines.
Which of the following antibiotics are bactericidal?
(piperacillin, cefotaxime, imipenem, clindamycin, rifampicin)
All except clindamycin (bacteriostatic lincosamide antibiotic)
Are macrolides bacteriocidal or bacteriostatic?
Can be either depending on their plasma concentration
What is the MOA of benzylpenicillin?
Inhibits cell wall synthesis
How does ceftriaxone work?
Cephalosporins, including Ceftriaxone, inhibit cell wall synthesis as do all beta-lactam antibiotics.
Their beta-lactam ring binds to proteins and prevents peptidoglycan cross-linkage in the bacterial cell-wall thus weakening it.
What does gentamicin do?
Gentamicin arrests bacterial protein synthesis by binding to the 30S ribosomal RNA subunit
What does ciprofloxacin do?
INhibits DNA gyrase
What does rifampicin do?
Rifampicin binds to the beta-subunit of DNA-dependent RNA polymerase, preventing bacterial protein synthesis.
What antibiotics cover MRSA?
Meropenem, Ciprofloxacin, Vancomycin, Clindamycin, Fusidic acid and Teicopleinin.
What antibiotics treat C. Diff?
Metronidazole and vancomycin
Which antibiotics provide good gram-negative cover?
Aztreonam
Gentamicin
Ciprofloxacin
How does amphotericin B work?
Creates pores in fungal cell membrane
Is miconazole absorbed orally?
No, all azoles EXCEPT miconazole are well absorbed orally
Which routes can amphotericin B be given?
IV only
Does the dose of ketoconazole need to be reduced in renal failure?
Ketoconazole is metabolised in the liver and inactive metabolites are excreted in the bile, hence no dose adjustment is required in renal failure.
How do azoles work?
By affecting funcal ergosterol synthesis
Can vancomycin cause ototoxicity?
Yes
Which antibiotic causes red discolouration of body fluids?
Rifampicin
How do aminoglycosides affect NDMRs?
Aminoglycosides increase potency of NDMRs by decreasing pre-junctional release of ACh and reducing the sensitivity of post-junctional receptors to ACh.
What effect can tetracycline have on children?
Discolouration of teeth
Which drug is associated with red man syndrome?
Vancomycin (histamine release and widespread rash)
Which antibiotics are significantly sensitive to beta-lactamases produced by bacteria?
Beta-lactam antibiotics are sensitive to beta-lactamase enzymes produced by resistant bacteria; different antibiotics in this class have differing degrees of sensitivity. Benzylpenicillin and Piperacillin are sensitive.
However Meropenem is very resistant to beta-lactamases, and Flucloxacillin is moderately beta-lactamase resistant.
