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Microbiology ` microbiology—aNtimicrobials Microbiology ` microbiology—aNtimicrobials SEcTioN ii 189

Cephalosporins
mecHaNism β-lactam drugs that inhibit cell wall synthesis Organisms typically not covered by 1st–4th
but are less susceptible to penicillinases. generation cephalosporins are LAME:
Bactericidal. Listeria, Atypicals (Chlamydia, Mycoplasma),
MRSA, and Enterococci.
cliNical Use 1st generation (cefazolin, cephalexin)—gram ⊕ 1st generation—⊕ PEcK.
cocci, Proteus mirabilis, E coli, Klebsiella
pneumoniae. Cefazolin used prior to surgery to
prevent S aureus wound infections.
2nd generation (cefaclor, cefoxitin, cefuroxime, 2nd graders wear fake fox fur to tea parties.
cefotetan)—gram ⊕ cocci, H influenzae, 2nd generation—⊕ HENS PEcK.
Enterobacter aerogenes, Neisseria spp., Serratia
marcescens, Proteus mirabilis, E coli, Klebsiella
pneumoniae.
3rd generation (ceftriaxone, cefotaxime, Can cross blood-brain barrier.
cefpodoxime, ceftazidime)—serious gram ⊝ Ceftriaxone—meningitis, gonorrhea,
infections resistant to other β-lactams. disseminated Lyme disease.
Ceftazidime—Pseudomonas.
4th generation (cefepime)—gram ⊝ organisms,
with  activity against Pseudomonas and gram
⊕ organisms.
5th generation (ceftaroline)—broad gram ⊕ and
gram ⊝ organism coverage; unlike 1st–4th
generation cephalosporins, ceftaroline covers
MRSA, and Enterococcus faecalis—does not
cover Pseudomonas.
aDVerse eFFects Hypersensitivity reactions, autoimmune
hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Low rate of cross-
reactivity even in penicillin-allergic patients.
 nephrotoxicity of aminoglycosides.
mecHaNism oF resistaNce Inactivated by cephalosporinases (a type of
β-lactamase). Structural change in penicillin-
binding proteins (transpeptidases).

β-lactamase inhibitors Include Clavulanic acid, Avibactam, CAST (eg, amoxicillin-clavulanate,
Sulbactam, Tazobactam. Often added to ceftazidime-avibactam, ampicillin-sulbactam,
penicillin antibiotics to protect the antibiotic piperacillin-tazobactam).
from destruction by β-lactamase.

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