Cephalosporins are a class of beta-lactam antibiotics (five generations) that inhibit bacterial cell wall synthesis by binding penicillin-binding proteins. They are among the most prescribed antibiotic classes and among the most disruptive to the gut microbiome.
Microbiome Disruption
Broad-spectrum cephalosporins (3rd/4th generation: ceftriaxone, cefepime) cause profound dysbiosis: deplete Firmicutes/Bacteroidetes commensals → Proteobacteria bloom → colonization resistance failure → increased risk of C. difficile and VRE secondary infection [1].
Siderophore-Cephalosporin Conjugate
Cefiderocol is the first FDA-approved siderophore-cephalosporin conjugate — a Trojan horse antibiotic that exploits bacterial iron uptake machinery. Cefiderocol is bound to a siderophore that mimics the pathogen's own iron chelator; the bacterium imports what it thinks is iron-loaded siderophore but instead internalizes a lethal antibiotic. This directly applies Karen's Brain Primitive 4 (metal dependencies as Achilles' heels) [2].
Beta-Lactamase Resistance
ESBLs and carbapenemases (beta lactamase) hydrolyze cephalosporins, conferring resistance. ESBL genes co-locate with metal resistance genes on shared plasmids (co selection).
Cross-References
- beta lactamase — resistance mechanism
- siderophores — cefiderocol Trojan horse concept
- vancomycin — alternative when cephalosporins fail
- colonization resistance — cephalosporin-induced destruction
- co selection — metal-antibiotic co-resistance