Enrichment culture coagglutination test for rapid, low-cost diagnosis of salmonellosis

Abstract

Specific diagnosis of salmonellosis by conventional culture and identification methods usually requires 2 to 4 days. Since Salmonella may be disseminated from infected individuals during this period, this amount of time required for diagnosis may be too slow to aid in epidemic control. To obtain earlier diagnoses of salmonellosis, a coagglutination test was used for rapid, simplified detection of Salmonella oranienburg antigens in enrichment broth cultures of fecal specimens from infants involved in a nursery outbreak. Two selective enrichment broths were used, selenite cystine and dulcitol selenite. These were compared in parallel for efficiency by subculture on deoxycholate lactose sucrose, MacConkey, xylose lysine deoxycholate, and tryptic soy lactose teepol agars. These overnight enrichment broth cultures of stool specimens were also examined by a coagglutination slide test with stabilized protein A-containing staphylococci sensitized with antisera for Salmonella antigens C1, E, and Vi. Of 113 diarrhea stool specimens tested, 86 were positive by conventional culture, 82 were positive by dulcitol selenite-coagglutination, and 55 were positive by selenite cystine-coagglutination. All these tests were negative on 50 stool specimens from infants in a noninfected nursery. Salmonellae were specifically detected in stool cultures within 20 h by the coagglutination technique. This early detection of Salmonella antigens provided a useful adjunct to culture for rapid diagnosis of salmonellosis.