Immune response to Bacteroides forsythus in a murine model

A murine skin abscess model was used to study the immune response to an acu te infection with Bacteroides forsythus. BALB/c mice were given subcutaneou s injections of either viable or heat-killed B. forsythus, while a third sh am-immunized control group received phosphate-buffered saline. Weights and lesion sizes were measured. Blood was collected from the heart and specific antibodies to B. forsythus measured by an ELISA. Swabs taken from the lesi ons and also from pooled blood were cultured anaerobically for viable B. fo rsythus. Viable B. forsythus-induced lesions reached maximum size at day 7. B. forsythus cells were recovered from lesions up to day 4 although none w ere cultured from blood samples. Heat-killed bacteria induced much smaller lesions. Serum antibody levels increased during the 9-day study period, bei ng significantly higher in mice injected with viable compared with heat-kil led B. forsythus. Antibody levels in sham control mice were significantly l ower than those seen in the other two groups. These results showed that a s ubcutaneous injection of viable cells of B. forsythus elicited a pronounced abscess formation and induce higher levels of specific antibodies compared with that produced by an injection of dead bacteria. This suggests that, a s with other periodontopathic organisms, this mouse model can be used to st udy the immune response to B. forsythus.