Britannica
Sources used in this answer
How are cephalosporins related to penicillins?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Antibiotic
Learn why antibiotics are important and how to prevent their overuse.
Cephalosporins and penicillins are closely related groups of antibiotics that share a fundamental mechanism of action: both inhibit the synthesis of the bacterial cell wall. Both classes are categorized as β-lactam antibiotics, as they rely on the β-lactam ring structure to exert their antibacterial effects.123
Despite these similarities, there are key distinctions:
- Chemical Structure: While both contain a β-lactam ring, their basic chemical structures differ, which influences their specific antibacterial spectra.1
- Clinical Use: Because their structures are similar, patients who are hypersensitive to penicillin may also experience allergic reactions to cephalosporins. Consequently, while cephalosporins are sometimes used as an alternative for penicillin-allergic patients, caution is required.132
- Origins: Penicillins are derived from the mold Penicillium, whereas cephalosporins were originally isolated from the fungus Cephalosporium acremonium.132
Both groups are considered relatively nontoxic and are widely used to treat a variety of bacterial infections.13