Detection of Salmonella typhimurium in oysters by PCR and molecular hybridization

Because shellfish (oysters, clams and mussels) are filter feeders, i.e., able to concentrate pathogens from the surrounding waters within their tissues, they have been widely associated with outbreaks illness. The incidence of salmonellosis caused by the consumption of raw or undercooked shellfish, is a primary concern of public health agencies. Then, in recent years, more rapid and specific methods based on the DNA sequence of salmonella genes have been developed to detect low levels of pathogens in environmental and food samples. In this study, we developed a sensitive method to detect low levels of Salmonella typhimurium in oyster tissues (0.1 cfu/g). This methodology consisted of dissection of the gastrointestinal oyster tract, pre-enrichment of the samples in nonselective medium, DNA extraction and polymerase chain reaction followed by molecular hybridization using a digoxygenin-labeled amplicon-derived probe. These results can benefit the public health agencies and shellfish producers concerning microbiological and quality aspects of the commercial oyster production.