Evaluation of bacteriophage amplification assay for rapid detection of Shigella boydii in food systems

This study was designed to investigate the possibility of using bacteriophages for the detection of viable Shigella boydii in food products. A Shigella bacteriophage belonging to a member of the Siphoviridae family was isolated from swine fecal samples. The free bacteriophages were highly stable against pH 4.0 to 9.0 and temperature change (z-value = 17.1 A degrees C). The bacteriophage amplification assay was able to selectively detect S. boydii in a bacterial mixture of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium. The number of S. boydii bacteriophages enumerated by the amplification assay was highly correlated with the number of viable S. boydii in single (r = 0.987) and mixed (r = 0.969) cultures. The bacteriophage-based detection of S. boydii was highly reproducible in lettuce (6.3 log CFU/ml and 4.9 log PFU/ml) and cooked chicken breasts (6.1 log CFU/ml and 6.0 log PFU/ml). These results suggest that the bacteriophage amplification assay can be used as an alternative method for rapid, selective, and cost-effective detection of S. boydii in food products, and provides useful information for designing a quick and simple detection kit.