Antimicrobial Susceptibility Pattern of Acinetobacter Baumannii and Rate of Carbapenem Resistance at a Tertiary Care Hospital in Karachi

Abstract

Objective:To know frequency of carbapenem resistance in Acinetobacter baumannii and its antimicrobial susceptibility pattern at PNS Shifa Hospital Karachi. Methodology:This study was carried out at PNS Shifa Hospital, Karachi, from 1st January 2015 till 31st October 2016. Samples from patients having different sites of infection were received in the laboratory from different wards of hospital and inoculated on culture plates. After 24 hours incubation, identification of non-lactose fermenter colonies of Acinetobacter baumannii was done by conventional methods. Antimicrobial susceptibility was recorded for ß-lactam group of antimicrobials, ß-lactam/ß-lactamase inhibitor combination group, tetracyclines, fluoroquinolones and aminoglycosides as per CLSI guidelines. Results: During the study period, a total of 117 Acinetobacter baumannii isolates were identified from culture of different samples representing 5.0% of all bacterial isolates (n=2352) and 7.5% of all Gram-negative bacilli (n=1559) throughout the hospital. Out of one hundred and seventeen isolates, 52.1% (n=62) were found carbapenem resistant. Higher percentages of Acinetobacter baumannii were isolated among samples received from medical wards (26.4%). Percentage of Acinetobacter baumannii isolated was highest from the blood culture specimens (22.2%). Isolates showed higher resistance against ceftriaxone (84.6%) followed by cotrimoxazole (65.8%) and ciprofloxacin (63.2%). Comparatively low resistance against doxycycline and minocycline (23.9%), and tigecycline (38.9%) was observed. Resistance pattern to other antimicrobials was gentamycin (54.7%), amikacin (55.6%), piperacillin-tazobactam (48.7%), cefoperazone-sulbactam (51.35%), meropenem (52.1%) and imipenem (52.1%). Conclusion: Carbapenem resistance in Acinetobacter baumannii is increasing and therapeutic options left to treat are highly toxic especially for patients with co-morbidities.