AUTHOR=Zhu Kui , Hölzel Christina S. , Cui Yifang , Mayer Ricarda , Wang Yang , Dietrich Richard , Didier Andrea , Bassitta Rupert , Märtlbauer Erwin , Ding Shuangyang 

TITLE=Probiotic Bacillus cereus Strains, a Potential Risk for Public Health in China

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00718

DOI=10.3389/fmicb.2016.00718

ISSN=1664-302X

ABSTRACT=<p><italic>Bacillus cereus</italic> is an important cause of foodborne infectious disease and food poisoning. However, <italic>B. cereus</italic> has also been used as a probiotic in human medicine and livestock production, with low standards of safety assessment. In this study, we evaluated the safety of 15 commercial probiotic <italic>B. cereus</italic> preparations from China in terms of mislabeling, toxin production, and transferable antimicrobial resistance. Most preparations were incorrectly labeled, as they contained additional bacterial species; one product did not contain viable <italic>B. cereus</italic> at all. In total, 18 <italic>B. cereus</italic> group strains—specifically <italic>B. cereus</italic> and <italic>Bacillus thuringiensis—</italic>were isolated. Enterotoxin genes <italic>nhe, hbl, and cytK1</italic>, as well as the <italic>ces</italic>-gene were assessed by PCR. Enterotoxin production and cytotoxicity were confirmed by ELISA and cell culture assays, respectively. All isolated <italic>B. cereus</italic> group strains produced the enterotoxin Nhe; 15 strains additionally produced Hbl. Antimicrobial resistance was assessed by microdilution; resistance genes were detected by PCR and further characterized by sequencing, transformation and conjugation assays. Nearly half of the strains harbored the antimicrobial resistance gene <italic>tet</italic>(45). In one strain, <italic>tet</italic>(45) was situated on a mobile genetic element—encoding a site-specific recombination mechanism—and was transferable to <italic>Staphylococcus aureus</italic> and <italic>Bacillus subtilis</italic> by electro-transformation. In view of the wide and uncontrolled use of these products, stricter regulations for safety assessment, including determination of virulence factors and transferable antimicrobial resistance genes, are urgently needed.</p>