Detection of Shiga toxin-producing Escherichia coli (STEC) in ground beef and bean sprouts: Evaluation of culture enrichment conditions. (January 2018)

• Record Type: Journal Article
• Authors: Amagliani, Giulia; Rotundo, Luca; Carloni, Elisa; Omiccioli, Enrica; Magnani, Mauro; Brandi, Giorgio; Fratamico, Pina
• Is Part Of: Food research international. Volume 103(2018)
• Page Start: 398
• Page End: 405
• Publication Date: 2018-01
• Subjects: STEC -- Enrichment medium -- Sprouts -- Ground beef -- Real-time PCR -- ISO/TS 13136:2012; Food -- Analysis -- Periodicals; Food industry and trade -- Periodicals; Food industry and trade -- Canada -- Periodicals; Food Technology -- Periodicals; Food -- Periodicals; Food-Processing Industry -- Periodicals; Aliments -- Industrie et commerce -- Périodiques; Aliments -- Industrie et commerce -- Canada -- Périodiques; Aliments -- Recherche -- Périodiques; Food industry and trade; Canada; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.foodres.2017.10.059
• Languages: English
• ISSNs: 0963-9969

Abstract

Abstract: The main purpose of this work was to evaluate culture enrichment conditions, with particular regard to those reported in ISO/TS 13136:2012, for STEC detection in food. The culture media evaluated included mTSB with novobiocin 0–16 mg/l (mTSB + N0–16 ) or acriflavin 12 mg/l (mTSB + A12 ); BPW; mBPWp with acriflavin 10 mg/l, cefsulodin 10 mg/l, vancomycin 8 mg/l (mBPWp + ACV); and mBPWp with cefsulodin 10 mg/l, vancomycin 8 mg/l (mBPWp + CV). They were used for the growth of STEC O157, O26, O103, O111, O145 and O104 in pure cultures or in artificially contaminated food matrices (ground beef, mung bean sprouts). STEC detection was accomplished using commercially available multiplex real-time PCR assays targeting stx 1 -stx 2 and eae, and serogroup-associated genes. More rapid multiplication of STEC in pure cultures occurred in mBPWp + CV, while an inhibitory effect of novobiocin and acriflavin was observed for some STEC serogroups in media with these selective agents. mBPWp + CV allowed the detection of all serogroups in bean sprouts when inoculated at levels as low as 1 CFU/25 g. A reduced novobiocin concentration of 2 mg/l in mTSB was required for STEC detection in ground beef samples. A temperature of 42 °C for the entire duration of the enrichment or 44 °C after an initial phase of 6 h at 37 °C was important to limit the multiplication of non-target bacteria. Results of this study suggest that media and protocols should be adapted to the food being analyzed, since protocols provided in official reference methods may produce insufficient sensitivity. Graphical abstract: Highlights: Culture enrichment conditions for STEC detection in food were evaluated. Media and enrichment protocols should be adapted to the food type analyzed. Enrichment at 42–44 °C was more effective than 37 °C for recovering low levels of STEC. Media provided in official reference methods may produce insufficient sensitivity.