USMLE Step 1 Antibiotics Exam Solved 100%

Penicillin mechanism - Answer binds to penicillin binding proteins in peptidoglycan (blocks transpeptidase crosslinking); activates autolytic enzymes penicillin use - Answer gram positives and syphilis penicillin toxicity - Answer hypersensitivity reactions, hemolytic anemia penicillinase resistant penicillins - Answer methicillin, nafcillin, dicloxacillin penicillinase resistant penicillin use - Answer Staph aureus penicillin resistant penicillin toxicity - Answer hypersensitivity; methicillin: interstitial nephritis aminopenicillins - Answer ampicillin, amoxacillin aminopenicillin mechanism - Answer same as penicillin but wider spectrum aminopenicillin use - Answer select gram positive and negative bacteria--H flu, E coli, Listeria, Proteus, Salmonella, enterococci aminopenicillin toxicity - Answer hypersensitivity, ampicillin rash, pseudomembranous colitis antipseudomonal drugs - Answer ticarcillin, piperacillin, carbenicillin antipseudomonal mechanism - Answer same as penicillin; wider spectrum antipseudomonal use - Answer Pseudomonas and gram negative rods antipsuedomonal toxicity - Answer hypersensitivity reaction beta lactamase inhibitor mechanism - Answer inhibit beta lactamase (protects penicillins from destruction) beta lacatamase drugs - Answer clavulanic acid, sulbactam, tazobactam bacteriostatic antibiotics - Answer erythromycin, clindamycin, sulfamethoxazole, trimethoprim, tetracycline, chloramphenicol bactericidal antibiotics - Answer vancomycin, fluoroquinolones, penicillin, aminoglycosides, cephalosporins, metronidazole 1st generation cephalosporins - Answer cefazolin, cephalexin 1st generation cephalosporin coverage - Answer gram positive cocci, Proteus, E coli, Klebsiella cephalosporin mechanism - Answer beta lactams; inhibit cell wall synthesis but less susceptible to penicillinases 2nd generation cephalosporins - Answer cefoxitin, cefaclor, cefuroxime 2nd generation cephalosporin coverage - Answer same as 1st plus H flu, enterobacter, Neisseria, Srratia 3rd generation cephalosporins - Answer ceftriaxone, ceftazidime, cefotaxime 3rd generation cephalosporin coverage - Answer serious gram negative infections; ceftriaxone: Neisseria, ceftazidime: pseudomonas 4th generation cephalosporins - Answer cefepime cephalosporin toxicity - Answer hypersensitivity, vitamin K deficiency, cross-hypersensitivity with penicillins, increase nephrotoxicity of aminoglycosides, reaction with alcohol aztreonam mechanism - Answer beta lactamase resistant monobactam; binds penicillin binding protein aztreonam use - Answer gram negative rods only aztreonam toxicity - Answer occasional GI upset imipenem/cilastin mechanism - Answer beta-lactamase resistant carbapenem; cilastin is a renal dihydropeptidase 1 (to decrease renal inactivation) imipenem use - Answer broad spectrum; gram + cocci, gram - rods and anaerobes (use limited to life-threatening or refractory infections because of side effects) imipenem toxicity - Answer GI distress, skin rash, CNS toxicity (seizures) at high plasma levels vancomycin mechanism - Answer inhibits cell wall mucopeptide formation by binding D ala D ala portion of cell wall precursors vancomycin use - Answer gram + only; use reserved for resistant infections--Staph aureus, enterococci, C diff vancomycin toxicity - Answer nephrotoxicity, ototoxicity, thrombophlebitis, red man syndrome, but well-tolerated in general resistance to vancomycin - Answer amino acid change from D-ala D-ala to D-ala D-lac 30s ribosomal inhibitors - Answer tetracyclins, aminoglycosides 50s ribosomal inhibitors - Answer clindamycin, chloramphenicol, erythromycin, linezolid, lincomycin aminoglycoside drugs - Answer gentamicin, neomycin, amikacin, tobramycin, streptomycin aminoglycoside mechanism - Answer inhibit formation of the initiation complex and cause misreading of mRNA; require O2 for uptake aminoglycoside use - Answer no anaerobe coverage; severe gram - rod infections; synergistic with beta lactams; neomycin for bowel surgery aminoglycoside toxicity - Answer nephrotoxicity (esp with cephalosporins), ototoxicity (esp with loop diuretics), teratogen aminoglycoside resistance - Answer drug modification via transferases tetracycline mechanism - Answer binds to 30s and prevents attachment of amino-acyl tRNA; limited CNS penetration tetracycline use - Answer borrelia burgdorferi, H. pylori, Mycoplasma. Rickettsia, Chlamydia (accumulates intercellularly); demeclocycline is ADH antagonist so used in SIADH tetracycline administration consideration - Answer absorption inhibited by milk, antacids, iron preparations; can be used in patients with renal failure because fecally eliminated tetracycline toxicity - Answer GI distress, teeth discoloration, inhibition of bone growth in children, photosensitivity tetracycline resistance - Answer decreased uptake or increased efflux macrolide drugs - Answer erythromycin, azithromycin, clarithromycin macrolide mechanism - Answer binds to 50s subunit and blocks translocation (binds to 23s RNA) macrolide use - Answer atypical pneumonias (mycoplasma, chlamydia, legionella), URIs, STDs, gram positive cocci (in pts allergic to penicillin), Neisseria macrolide toxicity - Answer prolonged QT, GI discomfort, acute cholestatic hepatitis, eosinophilia, skin rashes, increases serum concentration of theophyllines and oral anticoagulants macrolide resistance - Answer methylation of 23s binding site chloramphenicol mechanism - Answer binds to 50s ribosome, inhibits peptidyltransferase activity chloramphenicol use - Answer meningitis (H flu, Neisseria meningitis, Strep pneumo)