First detection of New Delhi metallo-β-lactamases variants (NDM-1, NDM-2) among Pseudomonas aeruginosa isolated from Iraqi hospitals

Background and Objectives: Multidrug resistance and in particular, carbapenem resistant Gram-negative bacteria is spreading worldwide at an alarming rate. Among the clinically significant carbapenemases, the New Delhi Metallo-β-lactamase (NDM) is one of the most formidable. NDM efficiently hydrolyses β-lactams and is the last-resort among carbapenems. Hence, therapeutic options for NDM producer bacteria become restricted to a handful of antibiotics. The present study was undertaken to detect the prevalence of the blaNDM-variants Metallo β- lactamases (MBLs) among isolates of Pseudomonas aeruginosa recovered from various clinical samples of hospitalized patients in Baghdad, Iraq. Materials and Methods: A total of 100 isolates of Gram-negative bacteria obtained from various clinical samples were subjected to antibiotic susceptibility testing by the disc-diffusion method against meropenem (10 μg), imipenem (10 μg), doripenem (10 μg), polymyxin B (10 μg), colistin (10 μg), amikacin (30 μg), gentamicin (10 μg), aztreonam (30 μg), ciprofloxacin (5 μg), levofloxacin (5 μg), ofloxacin (5 μg), cefepime (30 μg), ceftazidime (30 μg), piperacillin-tazobactam (100/10 μg), tigecycline (15 μg) and tetracycline (10 μg). The results were interpreted according to the guidelines suggested by the Clinical Laboratory Standards Institute. Presence of blaNDM was detected by PCR and it was confirmed by DNA sequencing of the gene present in the isolates that exhibited carbapenem resistance. Results: In the present study, four isolates of P. aeruginosa carried the blaNDM, three isolates harboured blaNDM-1 and one isolate harboured blaNDM-2. All isolates were resistant to imipenem and meropenem. The blaNDM-1 carrying isolates remained susceptible to colistin and β-lactamase inhibitors piperacillin-tazobactam. Conclusion: We are reporting emergence of the P. aeruginosa carrying the blaNDM-variant, which exhibited resistance to imipenem and meropenem for the first time in Iraq.