Role of Bacteroides uniformis in susceptibility of Ta:CF# 1 mice to infection by Treponema hyodysenteriae.

Among the various strains and colonies of mice tested specific-pathogen-free (SPF) Ta:CF#1 mice exhibited the highest susceptibility to Treponema hyodysenteriae infection. Staphylococcus epidermidis 1047, Streptococcus faecalis 2039, Lactobacillus murinus 3010, Escherichia coli 1049, and Bacteroides thetaiotaomicron 3008 were administered to the Ta:CF#1 mice. B. uniformis IK, which appeared to colonize in the breeding facility under SPF conditions, was isolated from the cecal content of a Ta:CF#1 mouse and identified in the mouse flora. Germfree mice were infected with these six bacteria and challenged with T. hyodysenteriae DJ70P3 to elucidate the causal relationship between these bacteria and the sensitivity of mice to T. hyodysenteriae infection. No cecal lesions were observed in gnotobiotic mice either monoassociated with T. hyodysenteriae DJ70P3 or B. uniformis IK or inoculated with T. hyodysenteriae DJ70P3 combined with the 5 a.m. strains. Gross cecal lesions appeared only in mice inoculated with T. hyodysenteriae DJ70P3 combined with B. uniformis IK. A new SPF mouse colony (CF#1/b Ta) established from gnotobiotic mice by inoculation with B. uniformis IK and the 5 laboratory stock cultures was as susceptible to T. hyodysenteriae as the original Ta:CF#1 mice. This suggests that B. uniformis IK plays an important role in the high susceptibility of Ta:CF#1 mice to T.hyodysenteriae.