Enteric Fever Caused by Salmonella enterica Serovars with Reduced Susceptibility of Fluoroquinolones at a Community Based Teaching Hospital of Nepal

Abstract

Enteric fever continues to be an important public health problem especially in developing countries of the tropical region including Nepal. In this study, we aimed to investigate the incidence of enteric fever associated with Salmonella enterica and determine its antimicrobial susceptibilities to therapeutic antimicrobials in a community based teaching hospital of Nepal. A total of 2,304 blood samples from suspected enteric fever patients attending Manmohan Memorial Teaching Hospital were processed with standard microbiological methods for the isolation and identification of bacterial pathogens. The Salmonella enterica clinical strains were subjected to antimicrobial susceptibility testing by Kirby-Bauer disk diffusion method, and the results were interpreted according to the criteria suggested by the Clinical and Laboratory Standards Institute (CLSI). A total of 245 (10.6%) cases of enteric fever associated with Salmonella enterica were confirmed by blood culture. Out of them, 162 (66.1%) were caused by Salmonella Typhi and 83 (33.9%) by Salmonella Paratyphi. On Kirby-Bauer disk diffusion antimicrobial susceptibility testing, Salmonella isolates were highly susceptible to cefixime (100%), ceftriaxone (100%), ampicillin (97.9%), cotrimoxazole (94.6%), azithromycin (96.7%), tetracycline (95.5%), and chloramphenicol (97.5%), respectively. Two hundred twenty-six (92.2%) of Salmonella isolates were nalidixic acid resistant with reduced susceptibility to ciprofloxacin (36.7%) and ofloxacin (54.8%), respectively. Although the rate of MDR Salmonella strains was very low (<5%), their reduced susceptibility to fluoroquinolones has restricted their routine empirical use. Third generation cephalosporins are the safest choice for empirical use but ampicillin, cotrimoxazole, azithromycin, and chloramphenicol can be effective alternatives.