Phenotypic methods for detection of metallobetalactamase in Meropenem resistant Pseudomonas aeruginosa and molecular detection of blaIMP & blaVIM genes carrying strains

Pseudomonas aeruginosa is one of the major organisms responsible for nosocomial infections such as pneumonia, UTIs, surgical site infections, and bloodstream infections.¹ High intrinsic and acquired resistance to many antimicrobial agents have allowed P. aeruginosa to persist in both community and hospital settings. This study was done to find the prevalence rate of Meropenem resistant Pseudomonas aeruginosa carrying metallobeta lactamase producing genes.

The study included a total of 100 non-duplicate clinically significant, random bacterial isolates obtained from a North Indian rural tertiary care hospital (Sri Guru Ram Das Institute of Medical Sciences and Research, Amritsar, India) from various clinical specimens, over a period of one year (January2012 to December 2012). Identification of organisms was done using the standard microbiological techniques as described by Colle et al 1996.⁷ The antimicrobial susceptibility testing was performed by Kirby Bauer disc diffusion method. To detect MBL producing isolates phenotypicaly, Disc potentiation test (DPT) and Double disc synergy test (DDST) were performed. PCR was performed on Meropenem resistant isolates to detect blaIMP and blaVIM genes.

Out of 100 examined isolates, 36% isolates were resistant to Meropenem. Out of these Meropenem resistant strains, 44.4%(16) P. aeruginosa isolates were MBL producers as detected by DDST method and 69.44%(25) isolates were MBL producers phenotypically by DPT method. PCR revealed prescence of blaVIM gene in 16.66%(6) of Meropenem resistant Pseudomonas aeruginosa isolates and 38.88% (14) isolates were found to be carrying blaIMP gene. Three isolate were shown to carry both blaIMP and blaVIM genes.

Resistance of P. aeruginosa isolates to Meropenem due to MBL enzymes is increasing in rural area. Resistance due to MBL has clinical significance, rapid detection of MBL producing strains followed by appropriate treatment is necessary to prevent the spreading of these organisms.