Antibiotics

Question 1

Penicillin

Answer 1

Bactericidal…binds PBPs, inhibits cross-linking of peptidoglycans…used for syphilis, Gram+…causes hypersensitivity

Question 2

Ampicillin/amoxicillin

Answer 2

Bactericidal…same MOA as PCN…used for H. flu, E. coli, Listeria, Proteus, Salmonella, Shigella…cause hypersensitivity, rash, pseudomembranous colitis…PCNase sensitive

Question 3

Oxacillin/Nafcillin/Dicloxacillin

Answer 3

PCNase resistant due to bulky R group, which blocks beta-lactamase access…used for S. aureus except MRSA…causes interstitial nephritis

Question 4

Ticarcillin/Piperacillin

Answer 4

Anti-pseudomonals…PCNase-susceptible…cause hypersensitivity

Question 5

Cephalosporins

Answer 5

Bactericidal, less susceptible to PCNase…don’t cover Listeria, atypicals, MRSA, enterococci…cause vitamin K deficiency, increased nephrotoxicity of aminoglycosides…low cross-reactivity with PCNs

Question 6

Aztreonam

Answer 6

Monobactam, beta-lactamase resistant…prevents peptidoglycan cross-linking by binding PBP-3…synergy with aminoglycosides…only useful for GNRs, in PCN-allergic or when aminoglycosides can’t be used due to renal toxicity…well-tolerated

Question 7

Carbapenems

Answer 7

Always give imipenem with cilastatin (inhibits renal enzyme dehydropeptidase which inactivates drug in renal tubules)…beta-lactamase resistant…cause seizures at high levels, skin rash

Question 8

Vancomycin

Answer 8

Inhibit cell wall peptidoglycan formation by binding D-ala-D-ala portion of cell wall precursors…bactericidal…only effective against gram+, esp. MRSA, C. diff…causes red man syndrome (diffuse flushing, pre-treat with anti-histamine)…also nephrotoxic, ototoxic, thrombophlebitis…resistance from mutation of D-ala-D-ala to D-ala-D-lac

Question 9

Aminoglycosides

Answer 9

Streptomycin, gentamicin, tobramycin, neomycin, amikacin…bactericidal…inhibit 30S ribosomal subunit by inhibiting formation of initiation complex…causes misreading of mRNA…requires O2 for uptake…nephrotoxic (esp. with cephalosporins), ototoxic (esp. with loop diuretics), neuromuscular blockade, teratogen…resistance via drug modification by bacterial enzymes

Question 10

Tetracyclines

Answer 10

Tetracycine, doxycycline, minocycline…bacteriostatic…bind to 30S and prevent attachment of aminoacyl-tRNA…limited CNS penetration…effective for Borrelia, Rickettsia, Chlamydia…can’t use in children under 8 due to teeth discoloration, decreased bone growth…photosensitivity in adults…resistance via efflux pumps

Question 11

Macrolides

Answer 11

Azithromycin, clarithromycin, erythromycin…bacteriostatic…act at 50S subunit to block translocation of growing polypeptide…MACRO toxicity (motility in GI tract, arrhythmia, cholestatic hepatitis, rash, eosinophilia)…P450 inhibitors, increase concentration of warfarin and theophylline…methylation of 23S rRNA binding site confers resistance

Question 12

Chloramphenicol

Answer 12

Bacteriostatic…acts at 50S subunit to inhibit peptidyltransferase…used for SHiN and Rickettsia, common in low-income countries…causes aplastic anemia…“grey baby syndrome” due to infants’ lack of glucuronyltransferase…resistance by plasma-encoded acetyltransferase

Question 13

Clindamycin

Answer 13

Same MOA as macrolides, bacteriostatic…effective for anaerobes above the diaphragm, MRSA…predisposes to C. diff

Question 14

Sulfonamides

Answer 14

Sulfamethoxazole, sulfisoxazole, sulfadiazine…bacteriostatic…inhibits folate synthesis by acting as PABA anti-metabolite, inhibits dihydropteroate synthase…displaces other drugs from albumin…hemolysis in G6PD, tubulointerstitial nephritis, photosensitivity, kernicterus in infants…resistance by altered dihydropteroate synthase, increased PABA synthesis, decreased drug uptake

Question 15

Trimethoprim

Answer 15

DHFR inhibitor…bacteriostatic…causes megaloblastic anemia, leukopenia, granulocytopenia

Question 16

Fluoroquinolones

Answer 16

DNA gyrase inhibitors (topoisomerase II and IV)…bactericidal…can’t take with antacids…effective against pseudomonas…causes tendonitis, tendon rupture, cartilage damage

Question 17

Metronidazole

Answer 17

Causes direct DNA damage through free radicals…bactericidal…anaerobes below diaphragm…has disulfiram-like effect with EtOH, metallic taste

Question 18

Rifampin

Answer 18

Inhibits DNA-dependent RNA polymerase…induces P450…orange body fluids

Question 19

Isoniazid

Answer 19

Inhibits mycolic acid synthesis…causes drug-induced lupus, neurotoxic, hepatotoxic…supplement with B6

Question 20

Pyrazinamide

Answer 20

Unknown MOA, maybe enhances phagolysosome acidity…causes hyperuricemia

Question 21

Ethambutol

Answer 21

Inhibits cell wall carbohydrate polymerization, blocks arabinosyltransferase…causes optic neuropathy, red-green color blindness