Diagnosis of Salmonella infections: specificity of indirect immunofluorescence for rapid identification of Salmonella enteritidis and usefulness of enzyme-linked immunosorbent assay.

An indirect immunofluorescence (IFL) method was used for diagnosis of infections caused by Salmonella enteritdis during an epidemic. Antiserum prepared against the synthetic disaccharide tyvelose 1 leads to alpha 3 D-mannose, representative of salmonella O antigen 9, covalently linked to bovine serum albumin, was used. Of 43 decal samples examined, 28 were positive for S. enteritidis by culture. IFL was applied (1) directly on fecal smears, (2) on enrichment broth cultures after incubation for 18-24 hr, and (3) on agar-grown colonies after incubation for 18-48 hr. The percentage of correctly identified Salmonella and the approximate gain of time for IFL as compared with conventional culture were 75% and 72 hr for (1), 89% and 48 hr for (2), and 100% and 24 hr for (3). Serum samples from 26 of the Salmonella-infected patients were examined by an enzyme-linked immunosorbent assay (ELISA). Twenty-four (92%) of the 26 patients acquired elevated ELISA titers of antibody to lipopolysaccharide, representative of Salmonella serogroup D.