Antimicrobial Susceptibility Profile of Gram-negative Bacteria Isolated from Clinical Samples in a Tertiary Care Hospital in Nepal

Abstract

Infections caused by Gram-negative bacteria and the rapid emergence of antimicrobial resistance (AMR) represent a serious global public health challenge. Low and middle-income countries, including Nepal, face a significant burden of AMR due to irrational antibiotic use. This study aims to assess the antibiotic susceptibility patterns of Gram-negative bacteria isolated from a tertiary care hospital in Nepal. A hospital-based cross-sectional study was conducted at the Department of Microbiology, Sukraraj Tropical and Infectious Disease Hospital, Kathmandu, from April to July 2023. A total of 737 clinical specimens including urine (n=263), sputum (n=260) and blood (n=214) were processed using standard microbiological techniques. Antimicrobial susceptibility testing was performed using the modified Kirby–Bauer disk diffusion method following Clinical and Laboratory Standards Institute guidelines. Extended-spectrum β-lactamase (ESBL) production was screened using ceftazidime and ceftriaxone disks and confirmed by double-disc synergy and combined disc methods. Among the 737 processed specimens, 76 (10.3%) showed bacterial growth, of these isolates 63 (82.9%) were Gram-negative bacteria. Escherichia coli (39.7%) was the most prevalent isolate followed by Salmonella Typhi (19.0%). Most Gram-negative isolates showed high resistance to amoxicillin (55.6%) and cefixime (41.3%). Chloramphenicol (96.8%), piperacillin/ tazobactam (95.2%) and meropenem (92.1%) were the most effective antibiotics. Among the 25 E. coli isolates, 13 (52%) were multidrug resistant and 12 (48%) were suspected ESBL producers, of which 10 were phenotypically confirmed. The high prevalence of multidrug resistance and ESBL production highlights the need for routine antimicrobial susceptibility testing and continuous surveillance to guide appropriate antibiotic therapy.