Evaluation of a multiplex selective enrichment broth SEL for simultaneous detection of injured Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes

Abstract

Although many rapid and high throughput molecular methods have been developed in the recent years for the multiplex detection of foodborne pathogens, the simultaneous recovery and enrichment of sublethally injured cells is still a problem that needs to be considered. Combined with previous established multiplex real-time PCR assay, the capability of simultaneous recovery and enrichment of sublethally injured Salmonella, E. coli O157:H7 and L. monocytogenes cells was evaluated in a multiplex selective enrichment broth SEL. The injured cells were obtained by heat shock. After evaluation of different procedures, 1 h of recovery period prior to 20 h of enrichment was proved to be necessary for the detection of less than 10 CFU/5 mL broth of injured L. monocytogenes. When the detection method was applied to artificially contaminated ground beef, all the three injured pathogens could be simultaneously detected without discrimination by real-time PCR combined with SEL broth, the detection limit was < 5 CFU/10 g ground beef. Comparatively, when BPW was employed as the enrichment broth in the same detection procedure, injured L. monocytogenes could not be detected if the initially spiked level was below 102 CFU/10 g ground beef. Considering the capability of co-enrichment and high detection effectiveness, the real-time PCR assay combined with SEL broth herein appears to be a promising tool for high-throughput screening of a large number of processed food samples, which require either single or multiple pathogen detection. More important, the sublethally injured foodborne pathogen cells were also detectable.

Multiplex Detection of Salmonella spp., E. coli O157 and L. monocytogenes by qPCR Melt Curve Analysis in Spiked Infant Formula

“…and E. coli O157, thus generating a greater interference with the growth of L. monocytogenes . This observation is in agreement with previous studies [ 26 , 27 ]. Additionally, none of the supplements, or selective compounds, added to the medium were able to improve the growth of L. monocytogenes , having the opposite effect.…”

Development of a multi-pathogen enrichment broth for simultaneous growth of five common foodborne pathogens

“…In particular, multi-pathogen detection on a single platform simplifies the detection procedure and has become a worldwide trend (Perry et al, 2007;Thong et al, 2014). However, the lower detection limit of these methods is a drawback, which indicates the importance of the implementation of an enrichment step prior to the detection of the bacteria by molecular biology techniques (Suo and Wang, 2014;Zheng et al, 2013). Some researchers have reported the use of multi-pathogen enrichment broths, specific for several target bacteria.…”

Multiplex real-time PCRs for detection of Salmonella, Listeria monocytogenes, and verotoxigenic Escherichia coli in carcasses of slaughtered animals

“…However, some studies reported that nonselective media may cause false negative results, especially by interference with complex background flora present in analysed samples (19). Therefore, the use of selective enrichment broth for simultaneous cultivation of multiple pathogens was also described (28), but it should be underlined that such media may inhibit or delay the growth of target microorganisms (31). Moreover, in the present study, one enrichment step was used for Gram-positive and Gram-negative microorganisms, whereas some authors have reported that detection of L. monocytogenes with PCR method is less sensitive and have recommended two enrichment steps (21).…”