Effects of anaerobic bacteria on Eimeria tenella infection in bacteria-free, monofloral, and conventional chickens.

Bacteria-free, monofloral, and conventional chicks were infected with Eimeria tenella. Monofloral chicks were established by inoculating birds in several gnotobiotic isolators with a single species of Escherichia coli or with one of three Bacteroides sp. isolates (No. 157, No. 202, or No. 366). Daily weights of individual birds were recorded for six days post-infection (PI). On Day 6 PI all birds were sacrificed and cecal lesions were scored. Conventional, infected birds lost weight on days 5 and 6 PI and showed severe lesions. Birds maintained as monofloral groups with isolates of Bacteroides sp. No. 157, No. 202 or E. coli showed equally severe lesions, but lost weight only on day 6 PI. Conventional, uninfected birds with no lesions, birds infected with Bacteroides sp. isolate No. 366 with mild lesions, and bacteria-free birds with mild to severe coccidial lesions all continued to gain weight on each day post-infection.