Detection of Salmonella typhimurium in raw meats using in-house prepared monoclonal antibody coated magnetic beads and PCR assay of the fimA gene.

A method for detection of Salmonella Typhimurium in meat samples that uses in-house monoclonal antibody (MAb) coated magnetic beads for immunomagnetic separation (IMS) associated with PCR amplification of the gene fimA was developed. An internal amplification control (IAC) of the PCR reaction was constructed. The fimA PCR has shown 100% sensitivity and specificity when tested with various bacteria. The detection limit of the IMS-PCR method, using a post-enrichment in BHI broth for 6 h between IMS and PCR, was 1-10 CFU/mL. The method proved to be rapid (27 hrs), highly sensitive (1-10 CFU/25 g), and specific for detection of S. Typhimurium from experimentally contaminated pork and chicken meat samples.

Shiga toxin-producing Escherichia coli (STEC) isolated from healthy dairy cattle in southern Brazil.

Over a period of 1 year, the production of verotoxin was investigated in 1127 Escherichia coli isolated from 243 dairy cattle from 60 small farms in southern Brazil. Vero cell assay was used to detect toxins in culture supernatants from E. coli isolated from bovine feces. Shiga toxin-producing E. coli (STEC) detection rates were 95% (57 of 60) for farms and 49% (119 of 243) for cattle. Prevalence of STEC-positive cattle in the farms ranged from 0 to 100%. Ninety-six percent (315 of 327) of the STEC isolates did not react in the panel of sera used for typing. Twelve isolates, all non-motile, belonged to serogroups previously associated with human diseases, and 67% (8 of 12) were of only two serotypes (O91:H- and sorbitol-fermenting O157:H-). These results indicate that dairy cattle from the region surveyed may be a source of STEC potentially pathogenic for humans.