It is produced by the strain of semisynthetic isoxazole penicillin. Cloxacillin is a semisynthetic beta-lactamase resistant penicillin antibiotic with antibacterial activity. It is a chlorinated derivative of oxacillin and is an antibiotic useful for the treatment of a number of bacterial infections. It binds to and inactivates penicillin-binding proteins (PBPs) located on the inner membrane of the bacterial cell wall, thus preventing the cross-linkage of peptidoglycans, which leads to an interruption of the bacterial cell wall and causes bacterial cell lysis. It is used against staphylococci that produce beta-lactamase, due to its large R chain, which does not allow the beta-lactamases to bind. It was discovered and developed by Beecham.