cephalosporin

Cephalosporins are a large family of beta-lactam antibiotics, cousins of penicillin, that share the same cell-wall-attacking strategy but tend to resist destruction better and cover a wider range of bacteria. If penicillin is the original model, cephalosporins are the upgraded line that engineers kept re-releasing in new versions to keep ahead of bacterial resistance.

Like all beta-lactams they bind penicillin-binding proteins and block cell-wall cross-linking, killing growing bacteria. They are conventionally sorted into generations: roughly speaking, earlier generations (such as cefazolin) favour Gram-positive bacteria, while later generations (such as ceftriaxone and cefepime) gain progressively more Gram-negative and resistant-organism coverage, often at the cost of some Gram-positive activity.

Cephalosporins are widely used precisely because of this breadth, but breadth has a downside: heavy use of broad-spectrum cephalosporins disrupts protective gut flora and is strongly linked to Clostridioides difficile infection. They also share partial cross-allergy with penicillins, and some interfere with vitamin K or alcohol metabolism, so they are not interchangeable choices to be reached for casually.