Background: Enteric fever is a burden in developing countries, in which poor sanitary conditions facilitate its persistence. Most cases are attributed to the bacterium Salmonella typhi. However, S. paratyphi A is an emerging agent of enteric fever. This trend is apparent in Kathmandu, Nepal, where the proportion of enteric fever cases at Patan Hospital caused by S. paratyphi A increased from 17.5% in 1993 to 34% in 2003 (1).

Salmonellatyphi and S. paratyphi A are atypical with respect to the majority of the genus Salmonella because they can survive and replicate in deeper tissues. Systemic dissemination causes organisms to be found in the gallbladder. This ability of S. typhi to remain in the gallbladder is considered central to the transmission of typhoid fever (2). An estimated 10% of untreated patients continue to shed bacteria for up to 3 months after infection, and up to 4% for more than 1 year. Most carriers are asymptomatic, and around 25% have no history of enteric fever (3). The role of chronic carriage of S. paratyphi A has received little attention, and the extent to which it contributes to S. paratyphi A infection is unknown.

Objective: To identify the burden of Salmonella carriage in an area of Kathmandu with a high incidence of enteric disease.

Methods: We assessed the bile and gallbladder from 404 consecutive patients undergoing cholecystectomy between June 2007 and June 2008 at Patan Hospital. Patients were examined before surgery, and surgeons diagnosed the cause of gallbladder symptoms on basis of the preoperative assessment, appearance during surgery, and postsurgical histopathologic examination. Bile was extracted from all removed gallbladders and cultured to isolate enteric bacteria. The Nepal Health Research Council approved this study.

Results: The Table shows data collected from 404 patients undergoing cholecystectomy. We cultured invasive Salmonella from the bile of 22 patients, yielding a prevalence rate in this population of 5.4%. We confirmed 12 isolates to be S. typhi and 9 to be S. paratyphi A, for a ratio of S. typhi to S. paratyphi A of 4: 3. The demographic characteristics of the population with Salmonella carriage were similar to the overall population undergoing cholecystectomy: 16 of 22 (72.7%) of Salmonella isolates were from women, and the median age in the female carriers was 35.9 years.