Recent paradigm shifts in the perception of the role of Bacillus thuringiensis in foodborne disease.

Plant protection products based on Bacillus thuringiensis have been used to fight agricultural pests for decades and are the world's most frequently applied biopesticide. However, there is growing concern that B. thuringiensis residues in food may occasionally cause diarrheal illness in humans. This has recently sparked a plethora of research activities and vivid discussions across the scientific community, competent authorities, and the public. To support this discussion, we provide a structured overview of the current knowledge on the role of B. thuringiensis as a causative agent of foodborne infections in humans and pinpoint research gaps that need to be addressed for improved risk assessment. We review (i) recent taxonomic changes in the B. cereus group; (ii) the role of B. thuringiensis in transforming agrosystems; and (iii) key considerations for assessing the hazard potential of B. thuringiensis strains detected in foods. We conclude that (i) the taxonomy of the B. cereus group is collapsing, (ii) B. thuringiensis based biopesticides play a key role in realizing the UN's sustainable development goals, and (iii) risk assessment needs to move from taxonomy-driven considerations to strain-specific identification of virulence and pathogenicity traits We also provide an overview of relevant risk-related data for commonly used biopesticide strains.

Further Insights into the Toxicity of Bacillus cytotoxicus Based on Toxin Gene Profiling and Vero Cell Cytotoxicity Assays.

Bacillus cytotoxicus belongs to the Bacillus cereus group that also comprises the foodborne pathogen Bacillus cereus sensu stricto, Bacillus anthracis causing anthrax, as well as the biopesticide Bacillus thuringiensis. The first B. cytotoxicus was isolated in the context of a severe food poisoning outbreak leading to fatal cases of diarrheal disease. Subsequent characterization of the outbreak strain led to the conclusion that this Bacillus strain was highly cytotoxic and eventually resulted in the description of a novel species, whose name reflects the observed toxicity: B. cytotoxicus. However, only a few isolates of this species have been characterized with regard to their cytotoxic potential and the role of B. cytotoxicus as a causative agent of food poisoning remains largely unclear. Hence, the aim of this study was to gain further insights into the toxicity of B. cytotoxicus. To this end, 19 isolates were obtained from mashed potato powders and characterized by toxin gene profiling and Vero cell cytotoxicity assays. All isolates harbored the cytK1 (cytotoxin K1) gene and species-specific variants of the nhe (non-hemolytic enterotoxin) gene. The isolates exhibited low or no toxicity towards Vero cells. Thus, this study indicates that the cytotoxic potential of B. cytotoxicus may be potentially lower than initially assumed.

Characterization of Bacillus cereus group isolates from powdered food products.

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.

Short communication: Staphylococcus aureus isolated from colostrum of dairy heifers represent a closely related group exhibiting highly homogeneous genomic and antimicrobial resistance features.

In heifers, intramammary infections caused by Staphylococcus aureus affect milk production and udder health in the first and subsequent lactations, and can lead to premature culling. Not much is known about Staph. aureus isolated from heifers and it is also unclear whether or not these strains are readily transmitted between heifers and lactating herd mates. In this study, we compared phenotypic characteristics, spa types, and DNA microarray virulence and resistance gene profiles of Staph. aureus isolates obtained from colostrum samples of dairy heifers with isolates obtained from lactating cows. Our objective was to (1) characterize Staph. aureus strains associated with mastitis in heifers and (2) determine relatedness of Staph. aureus strains from heifers and lactating cows to provide data on transmission. We analyzed colostrum samples of 501 heifers and milk samples of 68 lactating cows within the same herd, isolating 48 and 9 Staph. aureus isolates, respectively. Staphylococcus aureus strains from heifers, lactating herd mates, and an unrelated collection of 78 strains from bovine mastitis milk of mature cows were compared. With 1 exception each, characterization of all strains from heifers and lactating cows in the same herd yielded highly similar phenotypic and genotypic results. The strains were Staphaurex latex agglutination test negative (Oxoid AG, Basel, Switzerland) and belonged to agr type II, CC705, and spa types tbl 2645 and t12926. They were susceptible to all antimicrobial agents tested. In contrast, the strains from mature cows in other herds were spread across different clonal complexes, spa types, and SplitsTree clusters (http://www.splitstree.org/), thus displaying a far higher degree of heterogeneity. We conclude that strains isolated from colostrum of heifers and mastitis milk of lactating cows in the same herd feature highly similar phenotypic and genomic characteristics, suggesting persistence of the organism during the first and potentially subsequent lactations or transmission between heifers and mature herd mates.