Toxin-Producing Ability among Bacillus spp. Outside the Bacillus cereus Group

Abstract

A total of 333 Bacillus spp. isolated from foods, water, and food plants were examined for the production of possible enterotoxins and emetic toxins using a cytotoxicity assay on Vero cells, the boar spermatozoa motility assay, and a liquid chromatography-mass spectrometry method. Eight strains produced detectable toxins; six strains were cytotoxic, three strains produced putative emetic toxins (different in size from cereulide), and one strain produced both cytotoxin(s) and putative emetic toxin(s). The toxin-producing strains could be assigned to four different species, B. subtilis, B. mojavensis, B. pumilus, or B. fusiformis, by using a polyphasic approach including biochemical, chemotaxonomic, and DNA-based analyses. Four of the strains produced cytotoxins that were concentrated by ammonium sulfate followed by dialysis, and two strains produced cytotoxins that were not concentrated by such a treatment. Two cultures maintained full cytotoxic activity, two cultures reduced their activity, and two cultures lost their activity after boiling. The two most cytotoxic strains (both B. mojavensis) were tested for toxin production at different temperatures. One of these strains produced cytotoxin at growth temperatures ranging from 25 to 42°C, and no reduction in activity was observed even after 24 h of growth at 42°C. The strains that produced putative emetic toxins were tested for the influence of time and temperature on the toxin production. It was shown that they produced putative emetic toxin faster or just as fast at 30 as at 22°C. None of the cytotoxic strains produced B. cereus-like enterotoxins as tested by PCR or by immunological methods.The genus Bacillus consists of a heterogenic group of grampositive, endospore-forming, rod-shaped, facultative anaerobic bacteria that are widely distributed in nature. Due to their endospore-forming abilities, these bacteria tolerate adverse conditions better than the nonsporulating bacterial enteropathogens and may proliferate in a wide range of environments including water and processed and untreated foods.Bacillus cereus is the most important cause of food poisoning from this group due to its ability to produce enterotoxins and emetic toxin. The diarrheal type of food-borne illness is caused by three different heat-labile enterotoxins produced during vegetative growth of B. cereus in the small intestine after ingestion (9). The emetic type is due to the production of a heat-stable emetic toxin (cereulide) during growth in foods under various conditions (9). Other Bacillus species have generally been considered of little significance in food poisoning incidents (26), but their ability to produce both enterotoxins and emetic toxin has been increasingly recognized. It is mainly strains of B. subtilis, B. pumilus, and B. licheniformis that have been linked to incidents of food-borne illness (12,20,27), and it is believed that the enterotoxins produced by Bacillus spp. other than B. cereus are proteins transcribed from genes that are similar to those of B. cereus enterotoxins...

Alteration of Microbiological Load Quality of Rainwater Due to Atmospheric Exposure: An alternative Synergy to Potable Water Disinfection in Remote Communities of Niger Delta of Nigeria

“…Of public health concern is also their ability to produce toxins. Bacillus species are endospore-forming organisms and are able to increase rapidly in both water and non-processed or poorly processed foods [18]. The spores produced by them are often heat-resistant and as such require very high temperatures of exposure to radiation or chemicals to destroy them literally to become weak in pathogenicity.…”

Bacillus amyloliquefaciens bacteriemia in two preterm neonates: A significant catheter-related invasive infection in neonates

“…Bacillus species are widely distributed in nature and well known in the food industry as probiotics [1] and due to the ability of many strains to produce enterotoxins, a topic which has been reviewed recently [2][3][4][5]. Bacillus amyloliquefaciens, a gram-positive, rod-shaped, oval spore forming, aerobe bacterium of the family Bacillaceae, that is found commonly in soil, air [6], food, such as dried milk products [7], and many other sources, is the main strain implicated in production of α-amylase and protease [8,9].…”

Guidance on the assessment of the toxigenic potential of Bacillus species used in animal nutrition

“…The production of the B. cereus-like diarrhoeal enterotoxins by some strains of other Bacillus species was described in the SCAN opinion (EC, 2000), although such strains have so far not been associated with foodborne diseases. The current view is that the very few reports of B. cereus-like enterotoxins occurring in other species of Bacillus are likely to have resulted from a misidentification of the strain involved (From et al, 2005). The few incidents of food poisoning investigated where non-B.…”

“…To differentiate species within the B. subtilis group, partial sequences of the gyrA gene or gyrB genes may be needed in addition to the 16S rRNA gene sequences. These can be obtained using methods described in Chun and Bae (2000) and From et al (2005) for gyrA and Wang et al (2007) for gyrB.…”

“…This is essential as it determines whether the current guideline applies and, if so, the nature of the testing recommended. Partial sequences (approximately 500 bp) of the 16S rRNA gene can be amplified using methods described in Guinebretière et al (2001) and From et al (2005) and compared to sequences from databases. If the partial sequence does not provide a definitive identification, then the 16S rRNA gene should be fully sequenced (Guinebretière et al, 2001).…”