Emergence of carbapenem-resistant Acinetobacter baumannii in hospitals in Pakistan.

The emergence of pan-resistance in bacterial pathogens poses a threat to human health. Carbapenem-resistant Acinetobacter baumannii has emerged as a serious challenge, causing nosocomial infection and community-acquired outbreaks in hospitals globally, including in Pakistan. We collected 90 Acinetobacter isolates from patients with secondary or nosocomial infections from different hospitals in Pakistan and screened for carbapenem-resistant strains. Of the 90 isolates, 59 were resistant to carbapenems. Among oxacillinase -encoding genes, blaOXA-51-like was common in all isolates, including in combination with blaOXA-23-like in 14 isolates; however, blaOXA-24-like and blaOXA-58-like were completely absent. Among metallo-β-lactamase-encoding genes, only blaNDM-1 was found in one isolate, while the other three genes, blaIMP, blaVIM and blaSIM, were completely absent. None of the isolates was found to harbour the blaCTX-M gene. The isolates were also tested for susceptibilities to a panel of different antibiotics belonging to several classes. Of all the drugs tested, tigecycline was the most effective with 80 % sensitivity amongst isolates, followed by colistin with 50 % sensitivity. Three categories of resistance were found in these isolates: extreme drug resistance in 26, pan-drug resistance in 19 and multidrug resistance in 87 isolates. The isolates exhibited a high resistance to cephalosporins, trimethoprim-sulfamethoxazole and β-lactam antibiotics, followed by tetracycline and β-lactam/β-lactam inhibitor combination, fluoroquinolone and aminoglycosides. The results show a prominent level of antibiotic-resistance phenotypes in A. baumannii and strongly suggest the need for full-scale national surveillance of carbapenem-resistant A. baumannii with particular emphasis on the newly identified NDM-1 (New Delhi metallo-β-lactamase-1).