-Lactam - -lactamase inhibitor combinations as the choice therapy for multidrug resistant Acinetobacter

Acinetobacter, an important nosocomial pathogen, is capable of causing infectious outbreaks in critically ill patients which results into high morbidity and mortality worldwide. It is rated among top seven pathogens that disturb the health care delivery system. The situation has become complicated due to the organism’s capability to acquire diverse resistance mechanisms. This has resulted in the emergence of multidrug resistant and pan-drug resistant strains. A total of 100 clinical isolates of Acinetobacter spp. were evaluated against five β-lactam – β-lactamase inhibitor combinations by modified Kirby Bauer disc diffusion method using Mueller-Hinton agar. Zone sizes were interpreted according to CLSI 2012 guidelines. Out of 100 isolates, 85 were Acinetobacter baumannii, 9 were Acinetobacter johnsonii and 6 were Acinetobacter lwoffii. Eighty four isolates of A. baumannii, 8 isolates of A. johnsonii and all 6 isolates of A. lwoffii were multidrug resistant. One isolate from each of A. baumanni and A. johnsonii, and no isolate of A. lwoffii were susceptible to co-amoxiclav. Twenty eight isolates of A. baumanni, one isolate of A. johnsonii and no isolate of A. lwoffii were susceptible to ampicillin-sulbactam. Forty one (41) isolates of A. baumanni, one isolate of A. johnsonii and no isolate of A. lwoffii were susceptible to piperacillin-sulbactam. Eight isolates of A. baumanni, one isolate of A. johnsonii and no isolate of A. lwoffii were susceptible to piperacillin-tazobactam. Forty eight isolates of A. baumannii, one isolate of A. johnsonii, and no isolate of A. lwoffii were susceptible to cefoperazone-sulbactam. Cefoperazone-sulbactam was the most effective combination against 49% isolates of Acinetobacter. Ninety one percent isolates were resistant to piperacillin-tazobactam. Combinations having sulbactam were more effective as compared to others. This work also support the postulate that sulbactam, though not an antimicrobial, but does possess antibacterial activity against Acinetobacter species.