Betalactams

Beta-lactams are a broad class of antibiotics that share a beta-lactam ring in their chemical structures. They include penicillins, cephalosporins, carbapenems, and monobactams. Their primary mechanism is to inhibit bacterial cell wall synthesis by binding to penicillin-binding proteins, blocking transpeptidation and peptidoglycan cross-linking, which weakens the wall and causes cell lysis during growth.

Major groups and examples: Penicillins (penicillin G, amoxicillin); Cephalosporins (cephalexin, ceftriaxone); Carbapenems (meropenem, imipenem); Monobactams (aztreonam). Some beta-lactams are combined with beta-lactamase inhibitors to broaden activity, such as amoxicillin-clavulanate and piperacillin-tazobactam.

Resistance: Bacteria may produce beta-lactamases that hydrolyze the ring, or acquire altered PBPs with reduced affinity (as in MRSA). Other mechanisms include decreased permeability and efflux. Resistance is driven by overuse and poor stewardship; susceptibility testing guides therapy.

Clinical use and safety: Used for respiratory, skin, urinary, intra-abdominal, and other infections. Choice depends on spectrum and local resistance. Most beta-lactams are well tolerated; adverse effects include hypersensitivity and gastrointestinal upset. Some agents require dose adjustment in kidney disease; severe reactions are rare but can be life-threatening in allergic individuals.

History and significance: Penicillin was discovered by Alexander Fleming in 1928 and developed for clinical use in the 1940s. Beta-lactams remain among the most prescribed antibiotics, though resistance necessitates prudent use and ongoing surveillance.