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  • Characterization of Bacillu...
    Heini, Nicole; Stephan, Roger; Ehling-Schulz, Monika; Johler, Sophia

    International journal of food microbiology, 10/2018, Volume: 283
    Journal Article

    Mashed potato powder as well as powdered infant formula (PIF) are frequently contaminated with Bacillus cereus sensu lato (B. cereus s.l.), mainly with its spores. These products have also been implicated in foodborne illnesses. Here, we characterized B. cereus s.l. isolates originating from powdered products based on sporulation assays, toxin gene profiling, and panC typing combined with a SplitsTree analysis. Furthermore, cytotoxicity assays with B. cytotoxicus isolates were performed. 78% of PIF tested positive for B. cereus s.l., whereas 92% of all mashed potato powders were positive. In total, 43 isolates were further characterized. The nhe and cytK2 genes were most frequently detected. Moreover, a cereulide-producer was detected from PIF. Most isolates were assigned to panC group III, but members of group II, IV, V, and VII could also be found. Nine B. cytotoxicus were isolated out of nine mashed potato powders. All panC group VII isolates were positive for cytK1. Cytotoxicity assays of these nine isolates revealed one highly cytotoxic strain, while all other isolates exhibited no detectable cytotoxicity, underpinning that cytotoxicity of a certain B. cereus group strain cannot be deduced from the sole presence or absence of toxin genes. •B. cereus in mashed potato powders and PIFs pose a potential food safety risk.•Most B. cytotoxicus strains seem to be non-toxic.•One highly toxic B. cytotoxicus strain was detected.•The cytotoxicity of B. cytotoxicus was likely overestimated in the past.•One isolate (out of 19) from powdered infant formula harbored cereulide gene ces.