Influence of enrichment media and application of a PCR based method to detect Salmonella in poultry industry products and clinical samples

Abstract

To attempt the rapid detection of Salmonella enterica, we have coupled a culture procedure with PCR amplification of the genus-specific invE / invA genes. The method was applied to different kinds of samples from the poultry industry and evaluated by using hydrolyzed feather meal, meat meal, litter and viscera, all experimentally inoculated with a known number of Salmonella followed by cultivation in selenite–cystine broth prior to the PCR reaction. The expected 457 bp specific DNA fragment could be amplified from dilutions containing as few as 5.7 CFU, indicating that the PCR technique can be successfully coupled with culture in an enrichment broth to distinguish Salmonella species from other enteric bacteria present in samples from the poultry industry. Tetrathionate broth proved to be a much better enrichment media compared to selenite–cystine when the presence of Salmonella was evaluated by PCR in 1-day-old chicks experimentally infected with known numbers of Salmonella. Samples included cecal tonsils and viscera, collected at 48 h and 7 days postinfection. The PCR technique was more sensitive in detecting infected animals than the standard microbiological procedure, which detected only 47% of all PCR positive samples.