Copyright © 1992, American Society for Microbiology The Magnetic Immuno Polymerase Chain Reaction Assay for Direct Detection of Salmonellae in Fecal Samples

Direct polymerase chain reaction (PCR)-based detection with fecal specimens is hampered by inhibitory compounds, such as bilirubin and bile salts. These fecal compounds showed significant inhibition ofPCR at low concentrations (10 to 50 ig/ml). For direct PCR analysis, fecal samples must be diluted 500-fold to overcome inhibition. Therefore, the magnetic immuno PCR assay (MIPA), which combines immunomagnetic separation by using specific monoclonal antibodies and PCR, was used to directly detect salmonellae in feces from humans. Immunomagnetically extracted stool samples needed to be diluted only 10-fold when 1 ig ofT4 gene 32 protein was added to the PCR. The MIPA sensitivity obtained was 105 CFU/ml of feces. A panel of monoclonal antibodies specific for Sa1inonella serogroups A to E was used to extract salmonelHae from clinical samples. MIPA detection of salmonellae occurred with 11 out of 14 stool samples stored at 4°C for 2 months. MIPA detection of salmonellae in stool samples is a promising, fast method for detection and identification. Rapid and accurate diagnostic tests for salmonellae are needed by both the food industry and clinical laboratories. The official culture methods (Bacterial Analytical Manual! Association of Official Analytical Chemists) for the detection of salmonellae in food products require at least 5 days befor