Cell Wall Inhibitors Flashcards
Aztreonam spectrum:
Gram-negative rods (pseudomonas); monocyclic B-lactam use on penicillin-allergic patients
What are the penicillinase-sensitive penicillins?
Penicillin V (oral), Penicillin G (IV), Benzathine (IM injection)
spectrum of anti-psuedomonal penicillins
broad activity against gram(-)
pseudomonas
anti-pseudomonal penicillins
ticarcillin
piperacillin
What is administered with penicillinase-sensitive penicillins and why?
Probenecid to lengthen the half-life of the drugs; prevents renal excretion of weak acids
What are the penicillinase-resistant penicillins
Nafcillin, Dicloxicillin
What is the spectrum for penicillinase-sensitive penicillins?
Gram +
What is the spectrum for penicillinase-resistant penicillins
MSSA, other staph infections
What is ampicillin used specifically to treat?
pseudomembranous colitis
What is the spectrum for the aminopenicillins?
Wider spectrum, can treat Gram -
What is ampicillin used specifically to treat?
pseudomembranous colitis
Spectrum for Ist gen. Cephalosporins
Gram + cocci
Spectrum for 2nd gen. Cephalosporins
more Gram - activity, weaker Gram + activity
Spectrum for 3rd gen. Cephalosporins
Streptococci and more serious Gram -
can cross blood-brain barrier
What Cephalosporin generation is strong against C. diff?
3rd generation
Spectrum for 4th gen. Cephalosporins
Broad spectrum (Gram +, Gram -, pseudomonas)
Spectrum for 5th gen. Cephalosporins
MRSA that is resistant to other beta-lactams
What is the general mechanism of action for cephalosporins?
beta-lactams, bactericidal
sensitive to beta-lactamases
ticarcillin is often given in combination with _____ to reduce susceptibility to penicillinases
clavulanate
piperacillin is often given in combination with ____ to reduce susceptibility to penicillinases
tazobactam
why are penicillins combined with probenecid?
penicillins have a short half-life
probenecid impairs renal secretion of weak acids –> increases the life of penicillins
why are penicillins combined with beta-lactamase inhibitors?
beta-lactamase inhibitors bind irreversibly to beta-lactamases –> prevent the beta-lactamase cleavage of the beta-lactam ring –> allows the beta-lactam drug to be effective
T/F: Aztreonam is sensitive to beta-lactamases
True
Carbapenems spectrum
Broad spectrum, but MRSA is resistant; MUST BE GIVEN WITH CILASTATIN
Carbapenem delivery:
IV only (no oral); MUST BE GIVEN WITH CILASTATIN
Carbapenem side effects
GI stress, renal dysfunction
Describe how renal enzyme react with carbapenems
Form a toxic nephrotoxic metabolite; given with cilastatin to prevent this
Polymixin B mechanism of action
binds phophatidylethanolamine in membrane, creates holes; binds LPS and pulls out of cell membrane
Polymixin B spectrum
Treat multidrug resistant Gram - bacilli (pseudomonas and Klebsiella)
Polymixin B side effects
nephrotoxicity
Daptomycin mechanism of action
Bind cell membrane, aggregates, depolarizes membrane–>cell death/bactericidal
Daptomycin spectrum
only Gram + (particularly Vanco-resistant MRSA)
Daptomycin side effects
binds surfactants also, causing pneumonia
Daptomycin resistance mechanism
addition of positive lysines to cell surface; repels positive charged drug
Vancomycin spectrum
C. diff, MRSA; poorly absorbed
Vancomycin mechanism
Binds aa on cell wall precursor to inhibit release from bactroprenol carrier–>inhibits transglycosylase
Vancomycin resistance mechanism
enterococci (and some staphylococcus) change the aa sequence to prevent binding
What drugs will have increased efflux as the resistance mechanism?
cephalosporins, aztreonam
What drugs will have an altered drug target as the resistance mechanism?
beta-lactams, Vancomycin
What drugs will have drug inactivation as the resistance mechanism?
penicillins, cephalosporins,
