Enteropathogenic Potential of Bacillus thuringiensis Isolates from Soil, Animals, Food and Biopesticides

Abstract

Despite its benefits as biological insecticide, Bacillus thuringiensis bears enterotoxins, which can be responsible for a diarrhoeal type of food poisoning. Thus, all 24 isolates from foodstuffs, animals, soil and commercially used biopesticides tested in this study showed the genetic prerequisites necessary to provoke the disease. Moreover, though highly strain-specific, various isolates were able to germinate and also to actively move, which are further requirements for the onset of the disease. Most importantly, all isolates could grow under simulated intestinal conditions and produce significant amounts of enterotoxins. Cytotoxicity assays classified 14 isolates as highly, eight as medium and only two as low toxic. Additionally, growth inhibition by essential oils (EOs) was investigated as preventive measure against putatively enteropathogenic B. thuringiensis. Cinnamon Chinese cassia showed the highest antimicrobial activity, followed by citral, oregano and winter savory. In all tests, high strain-specific variations appeared and must be taken into account when evaluating the hazardous potential of B. thuringiensis and using EOs as antimicrobials. Altogether, the present study shows a non-negligible pathogenic potential of B. thuringiensis, independently from the origin of isolation. Generally, biopesticide strains were indistinguishable from other isolates. Thus, the use of these pesticides might indeed increase the risk for consumers’ health. Until complete information about the safety of the applied strains and formulations is available, consumers or manufacturers might benefit from the antimicrobial activity of EOs to reduce the level of contamination.

Performance Testing of Bacillus cereus Chromogenic Agar Media for Improved Detection in Milk and Other Food Samples

“…In our study, panC group IV was highly abundant among isolates from salads, vegetables, herbs and spices that may also include biopesticidal B. thuringiensis strains. Furthermore, cytK-2 was highly abundant among panC group IV strains [18,52]. This is concordant with our results as we identified cytK-2 highly abundant in panC/toxin gene profile combination IV/A (21.8% and 33.0% among target strains and sample isolates).…”

The Food Poisoning Toxins of Bacillus cereus

“…This is particularly problematic for the assessment of B. thuringiensis , which is frequently used as biopesticide worldwide [ 107 , 108 , 109 ]. B. thuringiensis has been isolated from a variety of foodstuffs and the presence of the enterotoxin genes nhe , hbl and cytK-2 has been shown, with similar percentages as for B. cereus [ 57 , 60 , 72 , 90 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 ], while ces genes have not been found [ 126 , 127 ]. Enterotoxin production and cytotoxic activity have also been shown [ 57 , 113 , 114 , 116 , 117 , 123 , 128 , 129 , 130 , 131 ], and B. thuringiensis could therefore be involved in food poisoning outbreaks [ 132 ].…”

Whole Genome Sequencing Reveals Biopesticidal Origin of Bacillus thuringiensis in Foods

“…B. thuringiensis belongs to the B. cereus sensu lato group and is genetically intermingled with the widely recognized foodborne pathogen B. cereus sensu stricto ( Ehling-Schulz et al, 2019 ; Carroll et al, 2020b ). In addition, B. thuringiensis strains from biopesticides can express medium to high levels of enterotoxins and were linked to outbreaks of diarrheal disease ( Johler et al, 2018 ; Schwenk et al, 2020 ; Bonis et al, 2021 ).…”