Rapid and simple method for detecting Salmonella in chicken feces using polymyxin-cloth enzyme immunoassay

The presence of three strains of Salmonella cells in chicken feces was detected by polymyxin-cloth enzyme immunoassay. A cotton swab-full of Salmonella-free chicken feces (containing an aerobic count of about 3x 10(7) cfu) was mixed with a small number of Salmonella typhimurium (6 or 12 cfu), Salmonella enteritidis (6 or 15 cfu) or Salmonella hadar (5 or 10 cfu) in 5 ml of brain-heart infusion medium supplemented with 0.5% yeast extract, 0.3% sodium hydrogen selenite, and 0.5% sodium cholate. After 20 h static incubation at 37 degrees C, heat-extracted lipopolysaccharide (LPS) antigens were captured by polymixin B adsorbed onto macroporous polyester cloth. The LPS antigens were then detected via sequential reactions with a mixture of mouse anti-Salmonella LPS antibody and rabbit Salmonella O antiserum followed by a mixture of horseradish peroxidase conjugates of antibody to mouse and rabbit immunoglobulin G. The total procedure took about 22 h. This method was also used to detect endogeneous Salmonella in feces of chicken inoculated with Salmonella and to measure the level of fecal Salmonella. This simple, rapid and sensitive method for Salmonella detection in feces should be useful not only for routine screening of Salmonella shedding in poultry, but also for Salmonella testing of stool from human patients and food handlers. (C) 1996 Academic Press Limited