Drug of choice for treating extended spectrum beta lactamase (ESBL) organism is:

Ans: B (Imipinem) Ref: Basic A- Clinical Pharmacology, Katzung 12th ed. P.800-802Explanation:Aztreonam is a monobactum and has structural similarities to ceftazidime; hence, its gram- negative spectrum is similar to that of the third- generation cephalosporins.It is stable to many b lactamases with the notable exceptions being AmpC b lactamases and extended-spectrum b lactamases.A carbapenem is indicated for infections caused by susceptible organisms that are resistant to other available drugs, eg, P aeruginosa, and for treatment of mixed aerobic and anaerobic infections.Carbapenems are highly active in the treatment of enterohacter infections because they are resistant to destruction by the b lactamaseCarbapenems are also the treatment of choice for infections caused by extended-spectrum b - lactamase (ESBL) producing gram-negative bacteria.Cefepime a fourth-generation cephalosporin is more resistant to hydrolysis by chromosomal b lactamases (eg, those produced by Enterobacter). However, like the third-generation cephalosporins, it is hydrolyzed by extended- spectrum b lactamases.So cefipime and ceftazidime cannot be used.