The safety of Bacillus subtilis and Bacillus indicus as food probiotics

Hong, H. A.
Huang, J.-M.
Khaneja, R.
Hiep, L. V.
Urdaci, M. C.
Cutting, S. M.

¹ School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
² National Institute of Vaccines and Biological Substances, Nha Trang, Vietnam
³ Laboratoire de Microbiologie, UMR5248 CNRS-Université de Bordeaux-ENITA, Gradignan, France

Correspondence Simon M. Cutting, School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK. E-mail: [email protected]

2007/1919: received 27 November 2007, revised 24 December 2007 and accepted 16 January 2008

Journal of Applied Microbiology 105(2):p 510-520, August 2008.

Aims

To conduct in vitro and in vivo assessments of the safety of two species of Bacillus, one of which, Bacillus subtilis, is in current use as a food supplement.

Methods and Results

Cultured cell lines, Caco-2, HEp-2 and the mucus-producing HT29-16E cell line, were used to evaluate adhesion, invasion and cytotoxicity. The Natto strain of B. subtilis was shown to be able to invade and lyse cells. Neither species was able to adhere significantly to any cell line. The Natto strain was also shown to form biofilms. No strain produced any of the known Bacillus enterotoxins. Disc-diffusion assays using a panel of antibiotics listed by the European Food Safety Authority (EFSA) showed that only Bacillus indicus carried resistance to clindamycin at a level above the minimum inhibitory concentration breakpoints set by the EFSA. In vivo assessments of acute and chronic dosing in guinea pigs and rabbits were made. No toxicity was observed in animals under these conditions.

Conclusions

Bacillus indicus and B. subtilis should be considered safe for oral use although the resistance of B. indicus to clindamycin requires further study.

Significance and Impact of the Study

The results support the use of B. subtilis and B. indicus strains as food supplements.