Affiliations: *Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok
**Disease Control Divesion, Health Department, Bangkok Metropolitan Administration
***WHO Salmonella and Shigella Center, Ministry of Public Health, Nonthaburi, Thailand
Source: Clinical Infectious Diseases 2004; 38: 1644-5
Sir—While management of asymptomatic food workers who are non-typhoidal salmonella (NTS) carriers needs additional convincing evidence, there is inadequate information about duration of excretion of NTS in healthy asymptomatic adults. We found in our previous report that 98.8% (254/257) of the asymptomatic adult NTS excretors had eradicated their initial NTS infection at the first bacteriologic assessment (day 12 after a positive screening culture),  which was a shorter time than an earlier study had reported.  An examination of 32 studies including 2,814 patients who were observed after being diagnosed with salmonella infection showed that median duration of NTS excretion was approximately five weeks, and that the duration of convalescent salmonella carriage varies with host factors, salmonella serotype, patient’s entry point, and criteria used for determining salmonella eradication. 
We had an opportunity to confirm our finding during a preparation for Asia Pacific Economic Cooperation Forum in Bangkok 2003. A screening for NTS carriers was performed by rectal swab culture in asymptomatic adult hotel workers. Hygienic education about enteric infection and prevention of spreading was given to all participants at the beginning of the study. A repeated rectal swab culture was performed in the initial NTS carries 21-28 days after the first culture. Microbiological methodology was the same as in our previous study. 
Three thousand asymptomatic adults from 16 hotels in Bangkok were include, 142 (4.7%) had Salmonella spp. isolated from a rectal swab culture. Eleven (7.7%) of the 142 initial NTS carriers had salmonelladetected in the second rectal swab culture; none had the initial Salmonella serotype which indicates 100% elimination rate of the initial Salmonella spp. Detection of the new Salmonella serotypes in the 11 initial NTS carriers indicates new infection. None of the NTS carries were treated with an antimicrobial drug before the second culture.
Our previous finding (that there was no benefit of antimicrobial therapy for adults NTS carriers)  was implemented; therefore, no antimicrobial drug was given to any adult salmonella carrier detected by this surveillance. They were assigned to work without food contact until a negative culture was obtained. The short duration of NTS excretion of healthy adults asymptomatic carriers, whose onset of NTS infection is unknown, is confirmed by this study.
Routine rectal swab culture and giving an antimicrobial drug to salonella carriers is still a common practice in several parts of the world. Evidence of short duration of NTS excretion and no benefit of antimicrobial treatment [1,3] lead to a strong recommendation against micrebiological screening and antimicrobial therapy, but for regular education and support for hygienic practice of workers.