Identification of Salmonella typhi in faecal specimens by an antiserum-agar method

Abstract

An antiserum-agar technique was evaluated as a method for detecting S. typhi in feces; 31 laboratory strains of S. typhi produced immunoprecipitate haloes during overnight growth on SS agar and blood-agar-base infusion agar (BAB) containing donkey antiserum to a vaccine strain of S. typhi. Other Salmonella spp. sharing O serogroup antigens with S. typhi also produced haloes when streaked in pure culture on SS-antiserum agar but not on BAB-antiserum agar. Results of this method on 141 consecutive fecal specimens [human] cultured on SS-antiserum agar were concordant with those of established isolation techniques on specimens from 6 of 7 suspected carriers of S. typhi. Ten other salmonellas were isolated from the fecal specimens but only S. javiana, like S. typhi a serogroup-D organism, yielded false-positive haloes on antiserum agar. The antiserum-agar technique offers promise as a means of screening for S. typhi in faecal cultures.