The detection of foodborne pathogens using bacteriophage-based AK assay
A sensitive and rapid phage-mediated AK assay was developed for the detection of 'E. coli' G2-2 and 'S. enteritidis '. In this assay, a bacteriophage is employed as a lytic agent for its target bacteria. The number of bacterial cells presence can be detected by measuring the degree of lysis and hence the release of intracellular adenylate kinase (AK). AK is assayed in the presence of excess ADP by measuring the formation of ATP by bioluminescence using the luciferase/luciferin reaction. In this study, the commercial ADP was purified for the assay using HPLC technique. For 'E. coli' G2-2 and 'S. enteritidis', the detection limits in pure culture were estimated to be approximately 1.2 * 103 CFU/ml and 1.5 * 103 CFU/ml, respectively. The effect of competitive flora on the ability of phages to infect host cells was also evaluated. The detection limit of 'E. coli' G2-2 in mixed culture was around 1.4 * 103 CFU/ml; for ' S. enteritidis', it was approximately 1.7 * 103 CFU/ml.