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

Abstract

The presence of three strains ofSalmonella cells in chicken feces was detected by polymyxin-cloth enzyme immunoassay. A cotton swab-full ofSalmonella -free chicken feces (containing an aerobic count of about 3×10 7cfu) was mixed with a small number of Salmonella typhimurium (6 or 12 cfu),Salmonella enteritidis (6 or 15 cfu) orSalmonella 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°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 rabbitSalmonella 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 endogeneousSalmonella in feces of chicken inoculated withSalmonella and to measure the level of fecalSalmonella . This simple, rapid and sensitive method forSalmonella detection in feces should be useful not only for routine screening ofSalmonella shedding in poultry, but also forSalmonella testing of stool from human patients and food handlers.