Detection of NDM-1 in Metallo-Beta-Lactamase-Producing Strains of Pseudomonas aeruginosa isolates from a Tertiary Hospital in Southwest Nigeria.

BACKGROUND

Metallo-beta-lactamase producingPseudomonas aeruginosa (MBL-PA) infections pose a major healthcare concern globally due to the associated extended morbidity, increased cost of treatment and high mortality.

OBJECTIVES

This study aimed to determine the prevalence of circulating MBL-PA strains and evaluate probable risk factors associated with the carriage of MBL-PA among patients in a selected South-western tertiary hospital in Nigeria.

METHODS

One hundred and forty-four isolates recovered from diverse clinical specimens were identified as Pseudomonas aeruginosa by conventional methods. Eight antibiotics were tested on the isolates using Kirby-Bauer disc diffusion technique. All carbapenem resistant isolates were phenotypically screened for MBL-production using the combined disc synergy test. The MBL-producing strains were evaluated for the presence of three MBL genes blaIMP, blaVIM-2 and blaNDM1 by Polymerase chain reaction (PCR).

RESULTS

Fourteen (9.7%) isolates were positive for metallobeta-lactamase production by combined disc synergy test. The MBL-producing strains were more commonly resistant to all the tested antibiotics except to piperacillin tazobactam and imipenem compared with the non MBL producing strains (p<0.05). Antibiotic use and the occurrence of multidrug resistance phenotype were significantly associated with MBLcarriage (p<0.05). Four (28.6%) MBL-PA isolates carried NDM-1 gene, while IMP and VIM-2 genes were not detected in any of the isolates.

CONCLUSION

The study demonstrated a low prevalence of NDM-1 in P. aeruginosa circulating among patients in this environment. This may be because carbapenems are seldom prescribed in our hospital or probably due to the existence of other MBL genes and non-enzymatic resistance mechanisms that we did not investigate. Studies that evaluate the level of carbapenem resistance via non-MBL production route could assist and improve future surveillance of these fast spreading genes.