Antibiotic resistance and β-lactam resistant genes among bacterial isolates from clinical, river water and poultry samples from Kathmandu, Nepal

Objective To assess the antibiotic resistance and beta-lactam resistance genes among bacterial isolates from clinical, river water and poultry samples. Methods Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were isolated from clinical, poultry and river water samples collected during 2020–22. They were subjected to antimicrobial susceptibility tests following the CLSI guidelines. The bacteria were screened for β-lactam resistance genes blaTEM, mcr-1, mecA and blaNDM-1. Results Among 2835 clinical samples, E. coli was the most frequently isolated bacterium (10.3%, 292), followed by S. aureus (6.0%, 169) and P. aeruginosa (4.0%, 143). Of the E. coli isolates, 64.4% exhibited multidrug resistance (MDR) and 43.8% were extended-spectrum β-lactamase (ESBL) producers, with 44.5% and 16.4% harbouring the blaTEM and mcr-1 genes, respectively. Among S. aureus isolates, 80.9% of methicillin-resistant strains (MRSA) carried the mecA gene, while 30.1% of metallo-β-lactamase (MBL)-producing P. aeruginosa were positive for the blaNDM-1 gene. In poultry samples, 30.4% of E. coli isolates harboured the blaTEM gene among 128 ESBL producers, and the prevalence of colistin-resistant isolates carrying mcr-1 was higher than in clinical samples. In contrast, the occurrence of ESBL-producing E. coli and MRSA, along with their associated resistance genes, was lower in water samples. Conclusions This study demonstrated widespread multidrug resistance (MDR) and ESBL production among clinical, poultry and river water bacterial isolates in the Kathmandu valley. Colistin-resistant E. coli carrying the mcr-1 gene, methicillin-resistant S. aureus (MRSA) with mecA and metallo-β-lactamase (MBL)-producing P. aeruginosa harboring blaNDM-1 were detected across sources. These findings emphasize an urgent One Health approach to curb the growing threat of antimicrobial resistance in the region.