Combination of Hydrophobic Filtration and Enrichment Methods for Detecting Bacillus cereus in Fresh-Cut Cabbage

Abstract

This study developed a rapid detection method for Bacillus cereus in fresh-cut cabbages. Fresh-cut cabbage samples were inoculated at 1-, 2-, and 3-Log CFU/g, and the pathogens were enriched in tryptic soy broth containing 0.15% polymyxin B at 30, 37, and 42oC to determine detection limit and appropriate enrichment temperature for multiplex PCR detection. Enriched bacterial cells in enrichment broth were collected in a hydrophobic filter prior to DNA extraction for multiplex PCR. Filters were resuspended in distilled water, and DNA was extracted from the suspension. DNA samples were further analyzed by multiplex PCR. Detection limit of the multiplex PCR was 5-Log CFU/mL. B. cereus cell counts were higher (p < 0.05) at 42oC than other temperatures. Detection rate of l-, 2-, and 3-Log CFU/g inoculated samples were 60, 80, and 100 % after enrichment respectively. However, when enriched samples were filtered with hydrophobic membrane filter, detection rates became 100%, regardless of inoculation level. Results indicate a combination of enrichment with hydrophobic filtration improves rapid detection efficiency of B. cereus in fresh-cut cabbage by multiplex PCR.