Toxin Profile, Biofilm Formation, and Molecular Characterization of Emetic Toxin–ProducingBacillus cereusGroup Isolates from Human Stools

Abstract

Emetic toxin-producing Bacillus cereus group species are an important problem, because the staple food for Korean is grains such as rice. In this study, we determined the prevalence (24 of 129 isolates) of emetic B. cereus in 36,745 stool samples from sporadic food-poisoning cases in Korea between 2007 and 2008. The toxin gene profile, toxin production, and biofilm-forming ability of the emetic B. cereus isolates were investigated. Repetitive element sequence polymorphism polymerase chain reaction fingerprints (rep-PCR) were also used to assess the intraspecific biodiversity of these isolates. Emetic B. cereus was present in 0.07% of the sporadic food-poisoning cases. The 24 emetic isolates identified all carried the nheABC and entFM genes and produced NHE enterotoxin. However, they did not have hemolysin BL toxin or related genes. A relationship between biofilm formation and toxin production was not observed in this study. The rep-PCR fingerprints of the B. cereus isolates were not influenced by the presence of toxin genes, or biofilm-forming ability. The rep-PCR assay discriminated emetic B. cereus isolates from nonemetic isolates, even if this assay did not perfectly discriminate these isolates. Further study on emetic isolates possessing a high degree of diversity may be necessary to evaluate the performance of the subtyping assay to discriminate emetic and nonemetic B. cereus isolates and could provide a more accurate indication of the risk from B. cereus strains.

Genetic diversity, antimicrobial resistance, toxin gene profiles, and toxin production ability of Bacillus cereus isolates from doenjang, a Korean fermented soybean paste

“…are genetically unrelated, the dendrogram in Figure 1 shows that the rep-PCR assay discriminates emetic B. cereus isolates from nonemetic isolates. This result is consistent with previous studies by Chon et al (2012) using DiversiLab andOh et al (2015) with (GTG) 5 primer. All 23 nonemetic doenjang isolates including the nonemetic toxin-producing reference strain ATCC14579 exhibited a similarity level of 26-100%, and 12 emetic doenjang isolates showed genetic diversity similar to nonemetic toxin-producing B. cereus (similarity level of 24-100%).…”

“…However, these did not possess the hbl toxin-producing genes and the cytK gene and were negative for HBL toxin production reaction. These characteristics of emetic B. cereus isolates in this study were consistent with previous studies (Ehling-Schulz, Vukov, et al, 2005;Kim et al, 2010;Oh et al, 2015).…”

“…All identified strains were suspended in 50% glycerol and tryptone soy broth (TSB; Oxoid) and stored at −70 °C until required for further use. B. cereus ATCC 14579 (diarrheal) and B. cereus Korean Food and Drug Administration (KFDA) 250 (emetic) were used as reference strains, in accordance with previous studies (Oh, Chang, Choi, Ok, & Lee, ).…”

Control ofBacillus cereusspore germination and outgrowth in cooked rice during chilling by nonorganic and organic apple, orange, and potato peel powders

“…Bacterial toxin‐mediated outbreaks caused by B. cereus occur worldwide, as indicated by recent reports of such outbreaks in Australia (May, Polkinghorne, & Fearnley, ), Austria (Schmid et al, ), France (Glasset et al, ), the United Kingdom (Nicholls et al, ), and Germany (Kamga Wambo et al, ). These outbreaks might be associated with morbidity and mortality in humans consuming food contaminated with B. cereus (Kim et al, ; Oh, Chang, Choi, Ok, & Lee, ; Tschiedel et al, ).…”

Detection of hblA and bal Genes in Bacillus cereus Isolates From Cheese Samples Using the Polymerase Chain Reaction

“…B. cereus strains encode two distinct toxins (3) and cause different syndromes, depending on the type of toxin produced (4). Emetic syndrome is caused by ingestion of a preformed heat-stable toxin called cereulide, encoded by the cer gene.…”