Beta lactamase resistant penicillin:

Ans: b (Cloxacillin) Ref: Tripahti, 6th ed, p. 699Classification1. Acid resistant alternative to pencillin G Phenoxymethyl penicillin (Penicillin V)2. Penicillinase resistant penicillins: Methicillin, cloxacillin3. Extended spectrum penicillina) Aminopenicillin: Ampicillin, bacampicillin, amoxicillinb) Carboxypenicillin: Caebenicillin, ticarcillinc) Ureidopenicillin: Piperacillin, mezlocillind) Ambinocillin: MecillinamBeta-lactamase inhibitors : Clavulanic acid, sulbactum, tazobactumResistanceResistance to penicillins and other b-lactams is due to one of four general mechanisms: (1) inactivation of antibiotic by b-lactamase, (2) modification of target PBPs, (3) impaired penetration of drug to target PBPs, and (4) efflux. b-Lactamase production is the most common mechanism of resistanceAltered target PBPs (penicillin binding proteins)are the basis of methicillin resistance in staphylococci and of penicillin resistance in pneumococci and enterococci. Resistance due to impaired penetration of antibiotic to target PBPs occurs only in gram-negative species because of their impermeable outer cell wall membrane, which is absent in gram-positive bacteria.NotesPiperacillin in combination with a beta- lactamase inhibitor (piperacillin -tazobactam) has the broadest antibacterial spectrum of the penicillins.Piperacillin is most effective anti-pseudomonal penicillin.