Prevalence of metallo-β-lactamase–producing Pseudomonas aeruginosa isolated from diabetic foot infections in Iraq

Metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa is a major cause of nosocomial infections. However, there is little information in Iraq regarding its prevalence in patients with diabetic foot ulcer. Carbapenems are efficient antibiotics against extended-spectrum β-lactamase–producing P. aeruginosa. However, there are many potential health risks associated with carbapenem-resistant P. aeruginosa. We aimed to determine MBL-producing P. aeruginosa isolated from diabetic foot ulcer infections. A total of 97 P. aeruginosa isolates were isolated from pus and deep tissue swabs of 282 patients admitted to Al-Sader hospital, Najaf City, Iraq, with diabetic foot infections from October 2017 to January 2018. All P. aeruginosa isolates were tested by the Kirby-Bauer disc diffusion method for evaluating 13 antibiotics. Phenotypic carbapenem resistance was confirmed by the combined disc test, double-disc synergy test, modified Hodge test and CHROMagar KPC agar. All phenotypic MBL-producing P. aeruginosa isolates were screened for bla(IMP), bla(NDM), bla(SIM), bla(SPM) and bla(VIM) genes by multiplex PCR. Of the 97 P. aeruginosa isolates, combined disc test and modified Hodge test revealed 12 isolates (12.4%) to be MBL producers, and ten (10.3%) displayed MBL production as accessed by CHROMagar KPC agar test. Nine isolates (9.3%) were carbapenemase producers by the imipenem and ceftizoxime double-disc synergy test. Of 12 phenotypic MBL-producing P. aeruginosa, PCR amplification confirmed 4 (33.3%) and 3 (25%) isolates harbouring bla(VIM) and bla(IMP) gene respectively, but none carried the bla(NDM), bla(SIM) or bla(SPM) genes. The steady and rapid increase of MBL production is worrisome and needs to be controlled through extensive studies and more judicious selection of antibiotics, especially carbapenems.