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

Abstract

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 bla _NDM-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 bla _NDM 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 bla _NDM, three isolates harboured bla _NDM-1 and one isolate harboured bla _NDM-2. All isolates were resistant to imipenem and meropenem. The bla _NDM-1 carrying isolates remained susceptible to colistin and β-lactamase inhibitors piperacillin-tazobactam.

Conclusion:

We are reporting emergence of the P. aeruginosa carrying the bla _NDM-variant, which exhibited resistance to imipenem and meropenem for the first time in Iraq.