antibiotics: beta-lactams (CILLIN, CEF, CEPH, PENEM, BACTAM)

what is a gram stain?

• microscopic method to detect bacterial and some fungal pathogens

• gram-(+): violet stain; clusters and chains

• gram-(-): pink stain; rods

what do GPC clusters indicate?

staph

what do GPC chains/pairs indicate?

strep

what do GNR rods indicate?

E. coli

what are beta-lactams?

penicillins, cephalosporins, carbapenems, monobactam

what is the MOA of beta-lactams?

inhibits bacterial cell wall synthesis by inhibiting PBP, leading to bacterial cell death

what are penicillins?

• low toxicity, no BBWs

• pregnancy category B

• largely indicated for strep

• 3 penicillins cover staph: dicloxacillin, nafcillin, oxacillin

• 1 anti-pseudomonal penicillin: zosyn

what is beta-lactam allergy?

• most important toxicity for beta-lactams

• penicillin allergy is the most commonly reported drug allergy: up to 10% of patients report PCN allergy; ~90% are not truly allergic

• accurate history is key to managing allergies

• need to differentiate between severe (anaphylaxis) and non-severe reactions

what are cephalosporins?

largely indicated for staph

what are the drug classes of cephalosporins?

• first generation: mostly gram-(+) coverage

• second generation: reduced gram-(+) increased gram-(-) coverage

• third generation: even further reduced gram-(+) coverage, and even more increased gram-(-) coverage

• fourth generation: gram-(+) coverage similar to first generation and gram-(-) coverage of third generation

what penicillin drugs cover staph?

cephalexin, cefadroxil, cefazolin

what are generation 3 cephalosporins?

cefpodoxime, ceftazidime (anti-pseudomonal), ceftriaxone

what are generation 5 cephalosporins?

• ceftraroline, cefderecol

• MRSA coverage

what are carbapenems?

• broadest spectrum class of beta-lactams: most reserved for drug-resistant infections

• relatively highest seizure risk among beta-lactams (still rare)

• low rate of allergy cross-reactivity with penicillins and cephalosporins

which carbapenem has no pseudomonas activity?

ertapenem

what is aztreonam (azactam)?

• bactams (monobactams)

• primary role: penicillin-allergic patients

• spectrum of activity:gram-(-) coverage only