Phenotypic and Genotypic Detection of Metallo-β Lactamase in Non-Fermenting Gram Negative Bacilli Obtained from Clinical Samples in a Tertiary Care Hospital in Nepal

Abstract

Introduction Non-fermenting Gram-negative bacilli (NFGNB) are significant nosocomial pathogens with limited treatment options. Among these, metallo-β-lactamases (MBL) are of major concern which hydrolyze carbapenems and contribute to antimicrobial resistance. This study aimed to determine the prevalence of MBL-producing non-fermenting gram negative bacilli in clinical specimens using both phenotypic and genotypic methods. Methods A descriptive cross-sectional study was conducted at Nepal Medical College Teaching Hospital from January to December 2024. A total of 16,954 clinical specimens were processed for culture and sensitivity testing. MBL production was detected phenotypically using the Imipenem-EDTA combined disc method. The presence of IMP and VIM genes was confirmed by conventional PCR. Results Among 16,954 specimens, 163 (0.96%) NFGNB isolates were identified, with Pseudomonas aeruginosa (52.1%) being the most prevalent, followed by Acinetobacter species (39.3%) and Burkholderia species (8.6%). MBL production was detected in 22 (13.5%) isolates: Pseudomonas aeruginosa (59.1%), and Acinetobacter species (40.9%). Genotypically IMP and VIM genes were found in 36.4% and 31.8% of MBL-positive isolates, respectively, while one isolate harbored both genes. Notably, 27.3% of phenotypic MBL producers tested negative for both IMP and VIM, suggesting the potential involvement of other MBL genes. Conclusion The significant prevalence of MBL-producing NFGNB, particularly among Pseudomonas aeruginosa and Acinetobacter species, highlights a serious challenge for antimicrobial therapy and underscores an urgent need for robust infection control and antimicrobial stewardship strategies.