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Characterization of Bacillus cereus group isolates from powdered food products


Heini, Nicole; Stephan, Roger; Ehling-Schulz, Monika; Johler, Sophia (2018). Characterization of Bacillus cereus group isolates from powdered food products. International Journal of Food Microbiology, 283:59-64.

Abstract

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.

Abstract

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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Food Safety and Hygiene
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Scopus Subject Areas:Life Sciences > Food Science
Life Sciences > Microbiology
Uncontrolled Keywords:Bacillus cereus group; Bacillus cytotoxicus; Mashed potato; Powdered infant formula; Vero cell assay
Language:English
Date:20 October 2018
Deposited On:12 Feb 2019 15:12
Last Modified:29 Jul 2020 10:12
Publisher:Elsevier
ISSN:0168-1605
OA Status:Green
Publisher DOI:https://doi.org/10.1016/j.ijfoodmicro.2018.06.019
PubMed ID:30099996

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