Identification of foodborne pathogens by nucleic acid hybridization

Nucleic acid hybridization methods have been developed and used to identify microorganisms in foods. Tests performed on mixed cultures save the time required to establish pure cultures. Enterotoxigenic or invasive strains of foodborne bacterial pathogens are detected with probes that identify genes responsible for virulence. Hybridization tests signal the presence or absence of a particular strain or an entire genus and are especially well suited for screening foods for specific pathogens. With the colony hybridization assay format, foodborne bacteria harboring a specific gene can be enumerated. However, hybridization tests require the presence of 10(5) to 10(6) cells to yield a positive result, thereby limiting sensitivity and necessitating a time-consuming growth step. In vitro DNA amplification techniques increase the amount of DNA segments 10(5)-10(6)-fold in 2 to 3 h, thus enhancing test sensitivity.