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. blaNDM−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 (blaNDM−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 blaNDM−1, mcr-1 and MexB genes respectively. Conclusion In our study, carbapenemase production (encoded by blaNDM−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.

Background: Pseudomonas aeruginosa is an opportunistic pathogen, which causes nosocomial infections in human. The rapid increase in drug resistance of this pathogen is a global concern. The aim of this study was to determine the clinical burden of P.aeruginosa, its antibiotic susceptibility pattern along with metallo-?-lactamase (MBL) detection.Methods: The descriptive cross-sectional study was conducted in Upendra Devkota Memorial National Institute of Neurological and Allied Sciences from January to August 2021. Isolation and identification of P. aeruginosa from clinical specimens was performed by using standard laboratory procedure. All bacterial isolates were phenotypically screened for multidrug resistance 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).Results: A total of 770 samples were processed of which 36 isolates of P. aeruginosa were obtained. P.aeruginosa was isolated mainly from tracheal aspirates, sputum, blood and urine. Among 36 isolates, 50% were found to be multidrug resistant (MDR). More percentage of P.aeruginosa isolates were found resistant to aztreonam, ofloxacin and levofloxacin (52.8%). Furthermore, this study reveals antibiotics like piperacillin/tazobactam and carbapenem were found to be good choice for the treatment of infection caused by this organism. Among MDR isolates 66.7% were found to be MBL producer.Conclusions: The data in this study highlights the prevalence of multidrug resistant, MBL producer, and colistin resistant P.aeruginosa in clinical specimens. In this study, carbapenems and piperacillin/tazobactam were found to be most effective antimicrobial drugs for empirical therapy in P.aeruginosa infections.Keywords: Metallo-?-lactamase; multidrug resistant; prevalence; Pseudomonas aeruginosa.