Isolation of Bacillus altitudinis A7 from Eimeria-immunized chickens and its inhibitory effect on Eimeria tenella

Eimeria spp. are responsible for chicken coccidiosis, the most important enteric protozoan disease in poultry, resulting in significant economic losses for the poultry industry. With the prohibition of antibiotic use in animal husbandry, researchers must find alternative preventive agents. The objective of this study was to isolate Bacillus strains and evaluate the anti-Eimeria tenella effects of B. altitudinis A7. In total, four Bacillus strains (A1, A5, A6, and A7) were isolated from the fresh feces of E. tenella-immunized chickens, and three Bacillus species, B. pumilus T246 (A1), B. altitudinis 41KF2b (A5 and A7), and B. cereus NS26 (A6), were identified with morphological and molecular methods. The consumption of B. altitudinis A7 by chickens significantly reduced oocyst production and the cecal lesion score after infection with E. tenella and significantly increased the expression of tight-junction proteins, interleukin-8 (IL-8), interleukin-10 (IL-10), and superoxide dismutase 1 (SOD1) relative to those in the E. tenella-infected, non-B. altitudinis A7-fed group (CON). B. altitudinis A7 also significantly increased the relative abundances of Pediococcus, Fournierella, Clostridium sensu stricto 1, CAG:352, and Tuzzerella compared with those in both the CON group and the normal control (N) group. These findings indicate that B. altitudinis A7 isolated from the feces of E. tenella-immunized chickens promoted host resistance to E. tenella.