Re-emergence of susceptibility to conventional first line drugs in Salmonella isolates from enteric fever patients in Nepal.

INTRODUCTION: Enteric fever is endemic in Nepal and poses a significant public health burden. The first-line drugs ampicillin, chloramphenicol, and cotrimoxazole have not been part of empirical therapy for two decades due to the development of multidrug-resistant Salmonella strains. The objective of this study was to determine the antibiogram pattern of Salmonella serovars isolated from the blood of clinically suspected enteric fever patients.

METHODOLOGY: A cross sectional study was carried out in a tertiary care hospital in Lalitpur, Nepal, between July 2011 and February 2012. Standard microbiological procedures were followed during collection and processing of blood samples, isolation and identification of Salmonella serotypes. The antimicrobial sensitivity of ampicillin, chloramphenicol, cotrimoxazole, nalidixic acid, and ciprofloxacin was determined using a modified Kirby-Bauer disk diffusion method as per the guidelines of the Clinical and Laboratory Standards Institute.

RESULTS: Out of 86 Salmonella isolates, 56 (65.1%) were Salmonella Typhi and 30 (34.9%) were Salmonella Paratyphi A. Salmonella Typhi were 100% sensitive to chloramphenicol, cotrimoxazole, and ciprofloxacin and 98.2% sensitive to ampicillin. Similarly, Salmonella Paratyphi A isolates were 100% sensitive to ampicillin and cotrimoxazole and 96.7% sensitive to chloramphenicol and ciprofloxacin. More than 90.0% of isolates were nalidixic acid resistant and none of the Salmonella isolates were multi-drug resistant.

CONCLUSIONS: This study revealed the increasing frequency of nalidixic acid-resistant Salmonella isolates, indicating the possibility of fluoroquinolone resistance in near future. Furthermore, re-emergence of susceptibility to conventional first-line drugs ampicillin, chloramphenicol, and cotrimoxazole supports the possibility of using these drugs in empirical therapy.