2024 STEP 1 FIRST AID – ANTIBIOTICS QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS

STEP 1 FIRST AID – ANTIBIOTICS QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS Penicillins MOA, Side Effects ANSWER IS - MOA: 1. Bind penicillin binding proteins 2. Block transpeptidase cross-linking of cell wall 3. Activate autolytic enzymes (Bactericidal) Side Effects: Hypersensitivity reaction (with cross alergenicity) Hemolytic anemia Penicillin G/Penicillin V Class, Target Orgs/Use, Administration ANSWER IS - Class - 1st generation PCNs Target Orgs/Use: Gram+ orgs (Grp A Strep, S. pneumoniae, Actinomyces) Treponema pallidum (syphilis) Bactericidal for Gram+ cocci, gram+ rods, gram- cocci and spirochetes Administration: PCN G - IV or IM (with anesthetic to increase t1/2) PCN V - oral Methicillin/nafcillin/dicloxacillin/oxacillin Class, Target Orgs/Use, Side Effects, Administration ANSWER IS - Class - 2nd generation PCNs (narrow spectrum, b-lactamase resistant due to bulkier Rgroup) Target Orgs/Use - S. aureus (excep MRSA-altered penicillin binding protein) Side Effects: Methicillin - allergic interstitial nephritis Nafcillin/Oxacillin - hepatitis (some hepatic excretion) Administration - Dicloxacillin oral Amoxicillin/Ampicillin Class, Target Orgs/Use, Side Effects, Administration ANSWER IS - Class - Aminopenicillins - 3rd generation PCNs (wider spectrum than 1st gen, b-lactamase sensitive) Target Orgs/Use: Gram- rods (H. flu, E. coli, Listeria, Proteus, Salmonella) and enterococcus "HELPS kill enteroccus" H. pylori triple therapy Side Effects - hypersensitivity reactions, ampicillin rash, pseudomembranous colitis Administration: Amoxicillin oral with food Can be given with b-lactam inhibitor to enhance spectrum EN Mezlocillin/Peperacillin Class, Target Orgs/Use ANSWER IS - Class - 4th generation PCN (Ureidopenicillins) - Extended sprectrum, susceptible to blactamase (use w/b-lactamase inhibitor) Target Orgs/Use - Pseudomonas and gram- rods Carbenicillin/Ticarcillin Class, Target Orgs/Use, Side Effects ANSWER IS - Class - 4th generation PCN (Carboxypenicillins) - Extended spectrum, b-lactamase sensitive (use w/b-lactamase inhibitor) Target Orgs/Use - Pseudomonas, gram- rods Side Effects - Disodium salts that can produce large salt load Clavulanic acid/Sulbactam/Tazobactam Class, MOA, Target Orgs/Use ANSWER IS - Class - b-lactamase inhibitors (given in combination with b-lactam abx) MOA - (No antimicrobial activity) covalent inhibitors of b-lactamase Target Orgs/Use: Effective in conjunction with 3-4 gen PCN against Gram- b-lactamases and S. aureus NOT effective for chromosomal b-lactamase of Pseudomonas, Enterobacter, Citrobacter, Serratia, B-lactam Resistance ANSWER IS - 3 Strategies: 1. Decrease penetration - Gram- orgs let b-lactam in via porin - change porin to restrict entry (ex Pseudomonas) 2. Alter PCN binding protein (ex MRSA via mec locus, S. pneumoniae via transformation) 3. B-lactamase