Brachyspira pilosicoli colonization in experimentally infected mice can be facilitated by dietary manipulation

The purpose of this study was to determine whether defined dietary manipulations would enhance colonization of mice experimentally challenged with the intestinal spirochaete Brachyspira pilosicoli. Weanling C3H/HeJ mice (n = 48) were fed either a standard balanced mouse diet or a diet supplemented with 50 p.p.m. zinc bacitracin (ZnB), with 50 % (w/w) lactose or with both supplements. Eight mice from each group were challenged orally with a human strain of B. pilosicoli (WesB), whilst four in each group acted as uninfected controls to evaluate the effects of the diets alone. The mice were kept for 40 days following challenge and faeces were collected every 3-4 days and subjected to culture and PCR for B. pilosicoli. Feeding ZnB reduced total volatile fatty acid production in the caecum. Feeding lactose alone doubled the weight of the caecum and its contents compared with control mice, and resulted in a relatively greater production of acetate, but a reduction in propionate and isovalerate production. These effects were negated by the addition of ZnB with the lactose. None of the mice fed the standard diet or receiving ZnB alone became colonized following experimental challenge. One of the mice receiving lactose was culture and PCR positive for B. pilosicoli on one sampling 1 week after inoculation, and one was positive on three samplings taken 20, 25 and 29 days after inoculation. All mice receiving both lactose and ZnB became colonized and remained so, with all samples being positive over the last seven samplings. The colonization was not associated with an end-on attachment of the spirochaete to the epithelial cells of the caecum, but colonized mice developed a specific humoral antibody response to the spirochaete.