Combination of bacteria concentration and DNA concentration for rapid detection of E. coli O157:H7, L. monocytogenes, and S. Typhimurium without microbial enrichment

Abstract

Microbial enrichment of bacteria is essential for detection because generally foodborne pathogens exist on food at very low concentrations. This study described a rapid and simple pretreatment method, combination of bacteria concentration and DNA concentration for detection E. coli O157:H7, L. monocytogenes, and S. Typhimurium on lettuce and beef. This method is based on filtration, modified PrepMan method, and real-time PCR. Filtration was used to concentrate the foodborne bacteria present in lettuce and beef. Modified PrepMan method was used to concentrate bacterial DNA by reducing DNA elution volume. As a result, the detection limits of E. coli O157:H7 and L. monocytogenes were improved from 103 CFU/g to 101 CFU/g, and from 102 CFU/g to 101 CFU/g in all foods, respectively. And the detection limits of S. Typhimurium were improved from 102 CFU/g to 100 CFU/g. Moreover, detection time including filtration, DNA extraction, and real-time PCR took only about 2 h. These results indicate that this method can be used as rapid detection method without time consuming microbial enrichment process.