Cephalosporins
Generations, Mechanism, Resistance, Spectrum & Clinical Use
Past RGUHS + MPMSU + MUHS · 17
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Introduction & chemistry
- Cephalosporins are semisynthetic, bactericidal β-lactam antibiotics derived from cephalosporin C, a natural product of the fungus Cephalosporium acremonium (now Acremonium chrysogenum) — first isolated by Giuseppe Brotzu (1948) from sewage-contaminated sea water off Sardinia.
- Active nucleus is 7-aminocephalosporanic acid (7-ACA) — a β-lactam ring fused to a six-membered dihydrothiazine ring (the cephem nucleus), versus the five-membered thiazolidine fusion of penicillins.
- Two side-chain positions tune the molecule: position 7 (R1) alters antibacterial spectrum & β-lactamase stability; position 3 (R2) alters pharmacokinetics (half-life, protein binding).
- Cephamycins (cefoxitin, cefotetan) carry an extra 7-α-methoxy group → enhanced β-lactamase stability and anti-anaerobic activity. Compared with penicillins, cephalosporins are water-soluble, relatively acid-stable and inherently penicillinase-resistant.
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Cephalosporins
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