Detection of carbapenemase-producing Pseudomonas aeruginosa by phenotypic and genotypic methods in a tertiary care hospital of East India.

Background: Carbapenemase-producing Pseudomonas aeruginosa is a serious threat in hospital infection due to its multidrug resistance.

Objective: The aim of the study was to determine the frequency of carbapenem resistance in clinical isolates of Pseudomonas aeruginosa and detect the presence of carbapenemase enzymes in carbapenem-resistant P. aeruginosa (CRPA) isolates by phenotypic and genotypic methods.

Methods: Double-disk synergy test [DDST] and combined disk synergy test [CDST]) was performed in CRPA isolates and the prevalence of blaKPC, blaNDM-1, blaIMP, blaVIM, blaSIM, blaSPM, blaGIM, and blaOXA-48 was determined.

Results: Of 559 isolates included in the study, a total of 102 isolates were resistant to carbapenem that accounted for overall 18.24% (102/559) prevalence. Of these 102 isolates, 89 (87.25%) isolates were positive by DDST and 95 (93.17%) isolates were positive by CDST. Of 102 CRPA isolates, blaVIM was detected in 30 isolates (30/102, 29.1%), followed by blaNDM-1 in 29 (29/102, 28.4%) isolates and blaSIM and blaGIM in 6 isolates each (6/102, 5.8%). A combination of two carbapenemase genes was detected in 12 isolates, with six (6/102, 5.88%) CRPA isolates harboring with both blaVIM and blaNDM-1 genes. Four isolates were found to harbor a combination of three carbapenem-resistant genes.

Conclusions: A high rate of carbapenemase production was observed in P. aeruginosa. Coproducers of multiple carbapenemases are also a cause of concern. An in-depth understanding of molecular mechanisms of resistance will be helpful in optimizing patient management and hospital infection control.