What are penicillins and what is their mechanism of action?

Penicillins are beta-lactam antibiotics that kill bacteria by inhibiting the synthesis of the bacterial cell wall. They bind to penicillin-binding proteins and prevent cross-linking of peptidoglycan, the structural component of the cell wall, causing cell lysis and death. Common penicillins include amoxicillin, ampicillin, penicillin G, and piperacillin. They are effective against many gram-positive bacteria and some gram-negative organisms.