A large class of antibiotics similar both chemically and in their mode of action to penicillin's. They are tetracyclic triterpene broad spectrum antibiotics first isolated from the culture filtrates of mediterranean fungus acremonium (cephalosporium acremonium). They contain the beta-lactam moiety thia-azabicyclo-octenecarboxylic acid also called 7-aminocephalosporanic acid and are effective against gram-positive bacteria.