ANTIBACTERIAL AGENTS are a subset of ANTIMICROBIAL AGENTS normally used to treat infections caused by bacteria, on which they have a selective toxic action. A distinction can be made between bacteriostatic’ agents that act primarily by arresting bacterial growth (e.g. sulphonamides, tetracycline antibiotics, chloramphenicol), as compared to the ‘bactericidal’ agents, which act primarily by killing bacteria (e.g. penicillin antibiotics, cephalosporin antibiotics, aminoglycoside antibiotics, isoniazid, rifampicin). See ANTIBIOTICS; ANTISEPTICS; SULPHONAMIDES.