Bacillus cereus is a well-known cause of food-borne illness, but infection with this organism is not commonly reported because of its usually mild symptoms. A fatal case due to liver failure after the consumption of pasta salad is described and demonstrates the possible severity of the emetic syndrome.

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Two thousand Bacillus cereus sensu lato isolates from food and environmental matrices were screened by PCR for the presence of cereulide-producing strains. This survey identified 73 potential emetic strains, most of which originated from non-random food and clinical samplings. None of the 460 Bacillus thuringiensis, Bacillus mycoides and Bacillus pseudomycoides strains were PCR-positive for the cereulide genetic determinants. The chromosomal and extrachromosomal gene pool diversity of a subset of 30 cereulide-producing strains was then assessed using multilocus sequence typing, large plasmid gel electrophoresis and Southern blot hybridization. The strain toxicity on boar sperm and cereulide production were also analysed. The most striking observation was the identification of two distinct clusters of cereulide-producing strains, with members of the second group (cluster II) identified as psychrotolerant B. weihenstephanensis able to grow at 8°C. Moreover, the location of the cereulide genetic determinants was shown to vary depending on the strain, indicating a probable genomic mobility.

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Honey bees harvest resins from various plant species and use them in the hive as propolis. While there have been a number of studies concerning the chemical composition of this antimicrobial product, little is known about selective behavior and bee preference when different potential plant sources of resin are available. The main objective of this paper was to investigate some aspects of behavioral patterns of honeybees in the context of resin acquisition. Samples of propolis originating from temperate zones of Europe and the supposed botanical precursors of the product were analyzed. Taxonomical markers of bud resins of two white birch species, aspen, black poplar, horse-chestnut, black alder, and Scots pine were determined through GC-MS analysis. All these trees have been reported as sources of propolis, but comparisons of the chemical composition of their bud resins with the compositions of propolis samples from seven European countries have demonstrated the presence of taxonomical markers only from black poplar, aspen, and one species of birch. This suggests selective behavior during the collection of bud resins by honeybees. To examine the causes of such selectivity, the antimicrobial properties of bud resins were determined. Horse-chestnut resins had lower antimicrobial activity than the other resins which did not differ significantly.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-016-0708-9) contains supplementary material, which is available to authorized users.

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The Bacillus cereus group, which includes entomopathogens and etiologic agents of foodborne illness or anthrax, persists in various environments. The basis of their ecological diversification remains largely undescribed. Here we present the genetic structure and phylogeny of 273 soil B. cereus s.l. isolates from diverse habitats in northeastern Poland, with samplings acquired from the last European natural forest (Białowieża National Park), the largest marshes in Europe (Biebrza National Park), and a farm. In multi-locus sequence typing (MLST), despite negative selection in seven housekeeping loci, the isolates exhibited high genetic diversity (325 alleles), mostly resulting from mutation events, and represented 148 sequencing types (131 STs new and 17 STs already described) grouped into 19 complexes corresponding with bacterial clones, and 80 singletons. Phylogenetic analyses showed that 74% of the isolates clustered with B. cereus s.l. environmental references (clade III), while only 11 and 15%, respectively, grouped with isolates of clinical origin (clade I), and B. cereus ATCC 14579 and reference B. thuringiensis (clade II). Predominantly within clade III, we found lineages adapted to low temperature (thermal ecotypes), while putative toxigenic isolates (cytK-positive) were scattered in all clades of the marsh and farm samplings. The occurrence of 92% of STs in bacilli originating from one habitat, and the description of new STs for 78% of the isolates, strongly indicate the existence of specific genotypes within the natural B. cereus s.l. populations. In contrast to the human-associated B. cereus s.l. that exhibit a significant level of similarity, the environmental isolates appear more complex. Thus we propose dividing B. cereus s.l. into two groups, the first including environmental isolates, and the second covering those that are of clinical relevance.