Detection of bla NDM−1, mcr-1 and MexB in multidrug resistant Pseudomonas aeruginosa isolated from clinical specimens in a tertiary care hospital of Nepal

Abstract Introduction Pseudomonas aeruginosa is an opportunistic pathogen, which causes healthcare-associated infections in immunosuppressed patients. They exhibit resistance to multiple classes of antibiotics via various mechanisms such as the over-expression of efflux pumps, decreased production of the outer membrane protein (D2 porin), over-expression of the chromosomally encoded AmpC cephalosporinase, modification of drugs, and mutation(s) at the target site of the drug. The bacteria also develop antibiotic resistance through the acquisition of resistance genes carried on mobile genetic elements. Limited data on phenotypic as well as genotypic characterization of MDR P. aeruginosa in Nepal infers the needs for this study. This study was carried out to determine the prevalence rate of metallo-β-lactamase (MBL-producer) as well as colistin resistant multidrug resistant (MDR) P. aeruginosa in Nepal and also to detect MBL, colistin resistance, and efflux pump encoding genes i.e. bla NDM−1 , mcr-1 and MexB respectively in MDR P. aeruginosa isolated from clinical samples. Methods/methodology A total of 36 clinical isolates of P. aeruginosa were collected. All bacterial isolates were phenotypically screened for antibiotic susceptibility using Kirby Bauer Disc Diffusion method. All the multidrug resistant P. aeruginosa were phenotypically screened for MBL producer by Imipenem-EDTA combined disc diffusion test (CDDT). Similarly, MIC value for colistin was also determined by broth microdilution method. Genes encoding carbapenemase (bla NDM−1 ), colistin resistant (mcr-1) and efflux pump activity (MexB) were assayed by PCR. Results Among 36 P. aeruginosa, 50% were found to be MDR among which 66.7% were found to be MBL producer and 11.2% were found to be colistin resistant. Among MDR P. aeruginosa, 16.7%, 11.2% and 94.4% were found to be harbouring bla NDM−1 , mcr-1 and MexB genes respectively. Conclusion In our study, carbapenemase production (encoded by bla NDM−1 ), colistin resistant enzyme production (encoded by mcr-1), and expression of efflux pump (encoded by MexB) are found to be one of the major causes of antibiotic resistance in P. aeruginosa. Therefore, periodic phenotypic as well as genotypic study in Nepal on P. aeruginosa would provide the scenario of resistance pattern or mechanisms in P. aeruginosa. Furthermore, new policies or rules can be implemented in order to control the P. aeruginosa infections

Nosocomial Isolates and Their Drug Resistant Pattern in ICU Patients at National Institute of Neurological and Allied Sciences, Nepal

Multidrug resistant organisms are increasing day by day and the cause is poorly known. This study was carried out from June 2011 to May 2012 at National Institute of Neurological and Allied Sciences Kathmandu, Nepal, with a view to determining drug resistant pathogens along with detection of extended spectrum β-lactamase (ESBL), AmpC β-lactamase (ABL), and metallo-β-lactamase (MBL) producing bacteria causing infection to ICU patients. A standard methodology was used to achieve these objectives as per recommendation of American Society for Microbiology. ESBL was detected by combined disc assay using cefotaxime and cefotaxime clavulanic acid, ABL by inhibitor based method using cefoxitin and phenylboronic acid, and MBL by imipenem-EDTA combined disk method. Two hundred and ninety-four different clinical samples such as tracheal aspirates, urine, pus, swabs, catheter tips, and blood were processed during the study. Most common bacteria were Acinetobacter spp. Of the total 58 Acinetobacter spp., 46 (79%) were MDR, and 27% were positive for ABL and 12% were for MBL. Of the 32 cases of Staphylococcus aureus, 18 (56%) were MDR. Findings of this study warrant routine β-lactamase testing in clinical isolates