,USMLE Step 1 – Antimicrobial Pharmacology High-Yield Q&A + Mechanisms – 2025 |
Kaplan Med Format
What antibacterials block cell wall synthesis by inhibition of peptidoglycan cross-linking?
Penicillin, Ampicillina, Ticarcillin, Piperacillin, Imipnem, Aztreoname, Cephalosporins
What is to MOA of Bacitracin and Vancomycin?
block peptidoglycan synthesis
What is the MOA of polymixins (used in resistant pseudomonas?
Disrupt bacterial cell membranes
What is the MOA of sulfonamides and trimethoprim?
block nucleotide synthesis
What is the MOA of fluroroquinolones?
Block DNA topoisomerases
What is the MOA of Rifampin?
Block mRNA synthesis
What is the MOA of chloramphenicol, Clindamycin, Macrolides (e.g Ezythromycin), Linezolid?
Block Protein Synthesis at 50S subunit
What is the MOA of Aminoglycosides and Tetracyclines?
Block protein synthesis and the 30S subunit
Which antibiotics are bactericidal?
Vacomycin, Fluoroquinolones, Penicillin, Aminoglycosides, Cephalosporins, Metronidazole ("Very Finely
Proficient At Cell Murder")
Penicillin
Use: Syphillis; gram-pos/ MOA: block penicillin-binding-proteins, block transpeptidase cross-linking of
cell wall, activate autolytic enzymes/ Resistance: Penicillinase(B-lactamase)-sensitive aka drug broken
down by enzyme in periplasmic space/ Tox: Hypersensitivity
Methicillin
MOA: Penicillanase-resistant penicillin--blocks transpeptidase and is reisstant to B-lactamase due to
bulkier R group/ Use: MSSA/ Tox: interstitial nephritis; hypersensitivty
Naficillin
MOA: Penicillanase-resistant penicillin--blocks transpeptidase and is reisstant to B-lactamase due to
bulkier R group/ Use: MSSA/ Tox: hypersensitivty
, Dicloxacillin
MOA: Penicillanase-resistant penicillin--blocks transpeptidase and is reisstant to B-lactamase due to
bulkier R group/ Use: MSSA/ Tox: hypersensitivty
Ampicillin
MOA: same as penicillin but has extended coverage/ Use: to inlcude gram negative rods, but is
penicillinase-SENSITIVE so typically add a B-lactamase inhibitor like clavulanic acid/ Amoxicillin (in same
class) has greater oral avaibility than Ampicillin/ Tox: psuedomembranous collitis from rebound C. Diff
infection; hypersensitivity
Amoxicillin
MOA: same as penicillin but has extended coverage/ Use: to inlcude gram negative rods, but is
penicillinase-SENSITIVE so typically add a B-lactamase inhibitor like clavulanic acid/ Amoxicillin has
greater oral avaibility than Ampicillin (in same class)/ Tox: psuedomembranous collitis from rebound C.
Diff infection; hypersensitivity
Ticarcillin
MOA: Same as penicillin with extnded coverage/ Use: Pseudomonas, but suceptible to penicillinase so
use with clavulanic acid (a B-lactamase inhibitor); other gram neg. rods/ Tox: hypersensitivity
Carbenicillin
MOA: Same as penicillin with extnded coverage/ Use: Pseudomonas, but suceptible to penicillinase so
use with clavulanic acid (a B-lactamase inhibitor); other gram neg. rods/ Tox: hypersensitivity
Piperacillin
MOA: Same as penicillin with extnded coverage/ Use: Pseudomonas, but suceptible to penicillinase so
use with clavulanic acid (a B-lactamase inhibitor); other gram neg. rods/ Tox: hypersensitivity
Clavulanic acid
B-lacatamase inhibitor added to penicillin antibiotics
Sulbactam
B-lacatamase inhibitor added to penicillin antibiotics
Tazobactam
B-lacatamase inhibitor added to penicillin antibiotics
What at the major toxiciites of cephalosporins?
Disulfram-like reaction with ethanol, they incresease the toxcicity of aminoglycosides, vit k deficiency--
can increase bkeeding risk, cross-hypersentitivty for 5-10% of patients with penicillin hypersensitivity
Cefazolin
Class: 1st gen cephalosporins/ Use: mostly only gram (+) but also Proteus, E.coli, Klebsiella
Kaplan Med Format
What antibacterials block cell wall synthesis by inhibition of peptidoglycan cross-linking?
Penicillin, Ampicillina, Ticarcillin, Piperacillin, Imipnem, Aztreoname, Cephalosporins
What is to MOA of Bacitracin and Vancomycin?
block peptidoglycan synthesis
What is the MOA of polymixins (used in resistant pseudomonas?
Disrupt bacterial cell membranes
What is the MOA of sulfonamides and trimethoprim?
block nucleotide synthesis
What is the MOA of fluroroquinolones?
Block DNA topoisomerases
What is the MOA of Rifampin?
Block mRNA synthesis
What is the MOA of chloramphenicol, Clindamycin, Macrolides (e.g Ezythromycin), Linezolid?
Block Protein Synthesis at 50S subunit
What is the MOA of Aminoglycosides and Tetracyclines?
Block protein synthesis and the 30S subunit
Which antibiotics are bactericidal?
Vacomycin, Fluoroquinolones, Penicillin, Aminoglycosides, Cephalosporins, Metronidazole ("Very Finely
Proficient At Cell Murder")
Penicillin
Use: Syphillis; gram-pos/ MOA: block penicillin-binding-proteins, block transpeptidase cross-linking of
cell wall, activate autolytic enzymes/ Resistance: Penicillinase(B-lactamase)-sensitive aka drug broken
down by enzyme in periplasmic space/ Tox: Hypersensitivity
Methicillin
MOA: Penicillanase-resistant penicillin--blocks transpeptidase and is reisstant to B-lactamase due to
bulkier R group/ Use: MSSA/ Tox: interstitial nephritis; hypersensitivty
Naficillin
MOA: Penicillanase-resistant penicillin--blocks transpeptidase and is reisstant to B-lactamase due to
bulkier R group/ Use: MSSA/ Tox: hypersensitivty
, Dicloxacillin
MOA: Penicillanase-resistant penicillin--blocks transpeptidase and is reisstant to B-lactamase due to
bulkier R group/ Use: MSSA/ Tox: hypersensitivty
Ampicillin
MOA: same as penicillin but has extended coverage/ Use: to inlcude gram negative rods, but is
penicillinase-SENSITIVE so typically add a B-lactamase inhibitor like clavulanic acid/ Amoxicillin (in same
class) has greater oral avaibility than Ampicillin/ Tox: psuedomembranous collitis from rebound C. Diff
infection; hypersensitivity
Amoxicillin
MOA: same as penicillin but has extended coverage/ Use: to inlcude gram negative rods, but is
penicillinase-SENSITIVE so typically add a B-lactamase inhibitor like clavulanic acid/ Amoxicillin has
greater oral avaibility than Ampicillin (in same class)/ Tox: psuedomembranous collitis from rebound C.
Diff infection; hypersensitivity
Ticarcillin
MOA: Same as penicillin with extnded coverage/ Use: Pseudomonas, but suceptible to penicillinase so
use with clavulanic acid (a B-lactamase inhibitor); other gram neg. rods/ Tox: hypersensitivity
Carbenicillin
MOA: Same as penicillin with extnded coverage/ Use: Pseudomonas, but suceptible to penicillinase so
use with clavulanic acid (a B-lactamase inhibitor); other gram neg. rods/ Tox: hypersensitivity
Piperacillin
MOA: Same as penicillin with extnded coverage/ Use: Pseudomonas, but suceptible to penicillinase so
use with clavulanic acid (a B-lactamase inhibitor); other gram neg. rods/ Tox: hypersensitivity
Clavulanic acid
B-lacatamase inhibitor added to penicillin antibiotics
Sulbactam
B-lacatamase inhibitor added to penicillin antibiotics
Tazobactam
B-lacatamase inhibitor added to penicillin antibiotics
What at the major toxiciites of cephalosporins?
Disulfram-like reaction with ethanol, they incresease the toxcicity of aminoglycosides, vit k deficiency--
can increase bkeeding risk, cross-hypersentitivty for 5-10% of patients with penicillin hypersensitivity
Cefazolin
Class: 1st gen cephalosporins/ Use: mostly only gram (+) but also Proteus, E.coli, Klebsiella
