Detection of Salmonella typhi carriers in food handlers by Vi serology in Lima, Peru.

The work described here sought to assess the merits of using an indirect hemagglutination test employing highly purified Vi antigen to screen a high-risk population for chronic S. typhi carriers in Lima, Peru. A total of 1,931 female food handlers over 30 years old were enrolled in the study. Indirect hemagglutination tests performed on these subjects' sera, taking a titer of 1:40 or more as positive, yielded 29 positive results. Subsequent bacteriologic testing performed on 26 of these 29 subjects identified four (15%) as S. typhi carriers. The procedure had a sensitivity of 79%, indicating that the prevalence of S. typhi carriers among the population studied was on the order of 262 per 100,000. It appears that Vi serology employing highly purified Vi antigen offers a practical and cost-effective way of screening for S. typhi carriers in both endemic and nonendemic typhoid fever areas.