All have beta lactam ring EXCEPT:
Penicillin
Linezolid
Cefotaxime
Imipenem
ANSWER: (B) LinezolidREF: Goodman and Gillman 11th edition page 780"Linezolid is a synthetic antimicrobial agent of the oxazolidinone class"The three classes of drugs which have beta lactam ring in its structure are:Penicillins consist of a thiazolidine ring connected to a b-lactam ring, to which is attached a side chainCephalosporins are produced from 7-aminocephalosporanic acid by the addition of different side chains. Modifications at position 7 of the b-Iactam ring alter antibacterial activity, while substitutions at position 3 of the dihydrothiazine ring alter the metabolism and pharmacokinetic properties.IILCarbapenems are b-lactams that have a broader spectrum of activity than most other fa- lactam antibiotics
Penicillin & Cephalosporin