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Flashcards in Antibiotics Deck (22):

Penicillin G, V: MOA and resistance

first penacillin. Works by binding penacillin binding proteins to prevent crosslinking of bacterial cell wall (blocks transpeptidases). also activates autolytic enzymes.
resistance from penicillinase in bacteria which leaves the beta lactam ring.
Penicillin G is IV and IM, penicillin V is oral.


Penicillin G and V toxicities and uses

gram positive organisms, treponema pallidum, N. menigitidis, actinomyces.
cause hypersensitivities and hemolytic anemia


Ampicillin, amoxicillin. MOA and resistance

similar drugs, but amoxicillin has better oral availability.
also bind penicillin binding proteins to prevent crosslinking of bacterial wall.
they differ from penicillins in that they have a broader spectrum of action. Still susceptible to penicillinase, though you can combine with clauvulanic acid to protect against beta lactamases.


Ampicillin, amoxicillin: clinical use and toxicity

extended spectrum penicillin: gram positives, but HELPSS more: Hib, enteroccoci and e coli, listeria, proteus, salmonella, shigella.
toxicity: hypersensitivity, pseudomembranous colitis


Oxacillin, nafcillin, dicloxacillin: MOA and resistance

mechanism: it's a penicillin, so it blocks crosslinking of the bacterial cell wall.
special because it is resistant to beta lactamases (bulky R-group blcoks access of beta-lactamase to the the beta lactam ring).
restance: MRSA has an altered penicillin binding site


oxacillin, nafcillin, dicloxacillin: use and toxicity

narrow-spectrum. Good for S. aureas, but not MRSA (MRSA is resistant because it has an alterned penicillin binding site)
toxicity: hypersensitivity, interstial nephritis


ticarcillin, piperacillin: mechanism and resistance

same as penicillin, but extended spectrum to cover pseudomonas and gram negative rods.
resistance: must use with a beta lactamase inhibitor, since it is susceptible to penicillinase.


What are the beta lactamase inhibitors

CAST: clavulanic acid, sulbactam, tazobactam


Mechanism of the cephalosporins; cidal/static,

these are also beta-lactam-like drugs. they inhibit cell wall synthesis. less susceptible to penicillinases. cidal


What organisms aren't usually covered by cephalosporins?

LAME: listeria, atypicals like chlamydia/mycoplasma, MRSA, enterococci. only exception is ceftarolin, which covers MRSA.


1st gen cephalosporin: coverage/uses

covers PEcK: proteus, E coli, klebsiella.
used prior to surgery to prevent S. aureus wound infections


2nd generation cephalosporins: coverage/uses

HEN PEcKS: Hib, Enetrobacter, Neisseria, Proteus, E coli, Klebsiella, serratia


3rd generation cephalosporins

used for secrious gram negative infections resistant to other beta lactams. Ceftriazone is used for menigitis and gonorrhea, ceftazidime is used for pseudomonas.



4th generation cephalosporin. covers pseudomonas and other gram positive organisms



broad coverage, including MRSA. does NOT cover pseudomonas


toxicity of cephalosporins

hypersensitivity, vitamin K deficiency. increases the toxicity of aminoglycosides


Azotreonam: mechanism

monobactam resistant to beta lactamases. prevents peptidoglycan cross-linking by binding to pencillin binding protein 3. synergistic with aminoglycosides.


azotreonam use and toxicity

gram negative rods ONLY. for penicillin allergic patients and those w/ renal insufficiency who cannot tolerate aminoglycosides
toxicity: usually nontoxic. no cross-allergenicity with penicillins


carbapenems: mechanism, special considerations

esp. imipenem. broad spectrum beta lactamase resistant carbapenem. always administered with cilastin to decrease inactivation of the drug in the renal tubules.


Carbapenems: use and toxicities

gram positive cocci, gram negative rods, anaerobes. toxicities: can cause GI distress, skin rash, and CNS toxicity/seizures at high levels.


Vancomycin mechanism and resistance.

inhibits cell wall peptidoglycan formation by binding D-ala-D-ala portion of cell wall precursors. bactericidial. resistance develops when the bacteria mutates to D-ala-D-lac


vancomycin use and toxicities

used for gram positive only (MRSA, eneterococci; used orally for C. diff).
toxicity: usually well-tolerated, but nephrotoxicity, ototoxicity, thrombophlebitis (vein inflammation). also causes red man syndrome if administered too quickly.