Bacillus species (Bacillus cereus, Bacillus clausii, Bacillus pumilus) carried in five commercial probiotic
products consisting of bacterial spores were characterized for potential attributes (colonization, immunostimulation,
and antimicrobial activity) that could account for their claimed probiotic properties. Three B.
cereus strains were shown to persist in the mouse gastrointestinal tract for up to 18 days postadministration,
demonstrating that these organisms have some ability to colonize. Spores of one B. cereus strain were extremely
sensitive to simulated gastric conditions and simulated intestinal fluids. Spores of all strains were immunogenic
when they were given orally to mice, but the B. pumilus strain was found to generate particularly high
anti-spore immunoglobulin G titers. Spores of B. pumilus and of a laboratory strain of B. subtilis were found
to induce the proinflammatory cytokine interleukin-6 in a cultured macrophage cell line, and in vivo, spores
of B. pumilus and B. subtilis induced the proinflammatory cytokine tumor necrosis factor alpha and the Th1
cytokine gamma interferon. The B. pumilus strain and one B. cereus strain (B. cereus var. vietnami) were found
to produce a bacteriocin-like activity against other Bacillus species. The results that provided evidence of
colonization, immunostimulation, and antimicrobial activity support the hypothesis that the organisms have
a potential probiotic effect. However, the three B. cereus strains were also found to produce the Hbl and Nhe
enterotoxins, which makes them unsafe for human use.
Bacillus species (Bacillus cereus, Bacillus clausii, Bacillus pumilus) carried in five commercial probioticproducts consisting of bacterial spores were characterized for potential attributes (colonization, immunostimulation,and antimicrobial activity) that could account for their claimed probiotic properties. Three B.cereus strains were shown to persist in the mouse gastrointestinal tract for up to 18 days postadministration,demonstrating that these organisms have some ability to colonize. Spores of one B. cereus strain were extremelysensitive to simulated gastric conditions and simulated intestinal fluids. Spores of all strains were immunogenicwhen they were given orally to mice, but the B. pumilus strain was found to generate particularly highanti-spore immunoglobulin G titers. Spores of B. pumilus and of a laboratory strain of B. subtilis were foundto induce the proinflammatory cytokine interleukin-6 in a cultured macrophage cell line, and in vivo, sporesof B. pumilus and B. subtilis induced the proinflammatory cytokine tumor necrosis factor alpha and the Th1cytokine gamma interferon. The B. pumilus strain and one B. cereus strain (B. cereus var. vietnami) were foundto produce a bacteriocin-like activity against other Bacillus species. The results that provided evidence ofcolonization, immunostimulation, and antimicrobial activity support the hypothesis that the organisms havea potential probiotic effect. However, the three B. cereus strains were also found to produce the Hbl and Nheenterotoxins, which makes them unsafe for human use.
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