ORIGINAL ARTICLE Inclusion of Bacillus amyloliquefaciens strain TOA5001 in the diet of broilers suppresses the symptoms of coccidiosis by modulating intestinal microbiota Takamitsu TSUKAHARA, 1 Ryo INOUE, 2 Keizo NAKAYAMA 1 and Takio INATOMI 3,4 1 Kyoto Institute of Nutrition & Pathology, Ujitawara, 2 Kyoto Prefectural University, Shimogamo, Kyoto, 3 TOA Pharmaceutical Co. Ltd., and 4 Inatomi Animal Hospital, Tokyo, Japan ABSTRACT Coccidiosis is an intestinal parasitic infection and one of the most prevalent and economically damaging diseases of chickens. Furthermore, coccidia-induced mucogenesis promotes secondary colonization by Clostridium perfringens,a major pathogen of chickens that causes necrotic enteritis. Our previous work found that supernatant of a culture of Bacillus amyloliquefaciens strain TOA5001 (BA) inhibited the growth of C. perfringens on Gifu anaerobic broth med- ium. Accordingly, we evaluated the effectiveness of dietary BA administration in inhibiting C. perfringens colonization of the intestine in broilers that were experimentally infected with coccidia. Ten healthy broilers from a BA-supplemen- ted (2 9 10 5 colony-forming units/g of feed) broiler group and 10 from a non-treated group were challenged with Eimeria tenella and E. maxima (5000 oocysts of each species/chick) at 28 days old. At 36 days old, five chicks from each group were slaughtered, whereas the remaining five in each group were killed at 49 days old. Dietary BA admin- istration into Eimeria-challenged birds reduced coccidial symptoms such as intestinal lesions. It also modified the cecal microbiota through suppressing C. perfringens and E. coli colonization, and inducing domination of Faecalibacterium prausnitzii, the Lactobacillus group and unknown Lachnospiraceae genera by bacterial DNA-based metagenome analy- ses. B. amyloliquefaciens TOA5001 supplementation suppressed the symptoms of coccidiosis by modulating cecal microbiota in Eimeria-challenged broilers. Key words: Bacillus amyloliquefaciens, broiler, cecal microbiota, Clostridium perfringens, coccidial infection. INTRODUCTION Coccidiosis is an intestinal parasitic infection and one of the most prevalent and economically damaging dis- eases of chickens. Parasitic protozoa of the genus Eime- ria infect the intestinal tract and cause tissue damage, resulting in interruption of feeding and digestive pro- cesses, poor nutrient absorption, dehydration, blood loss and increased susceptibility to other disease agents (Morris & Gasser 2006). The clinical signs of coccidiosis include mortality, morbidity, diarrhea and bloody feces (Williams 1999). However, control and treatment of the disease increases production costs (Hafez 2008). Indeed, anti-coccidial drugs and live vaccines are the main control measures for coccidiosis, but there are increasing problems with prolonged drug usage and the high cost of vaccines. Therefore, alternative strate- gies are needed for safety and cost effectiveness of coc- cidiosis treatment in chickens (Dalloul et al. 2006; Williams 2006). Probiotics have been among the most promising alternative coccidiosis control strategies investigated (Dalloul et al. 2003; Lee et al. 2007). For example, in a previous study conducted in our laboratory, a diet- ary probiotic mixture containing Bacillus mesentericus, Clostridium butyricum and Streptococcus faecalis adminis- tration was effective in preventing coccidial infection in broilers (Hayakawa et al. 2014). The effectiveness of this probiotic against coccidiosis was associated with stimulation of total immunoglobulin A (IgA) production in the intestine, and elongation of the villous height in the jejunum. Bacillus amyloliquefa- ciens strain TOA5001 (BA), a spore-forming bac- terium, produces the anti-fungal factor Bacillomycin Lc, and the culture supernatants of this strain were Correspondence: Takamitsu Tsukahara, Kyoto Institute of Nutrition & Pathology, Ujitawara, Kyoto 610-0231, Japan. (Email: tsukahara@kyoto-inp.cc) Received 9 May 2017; accepted for publication 17 November 2017. © 2017 Japanese Society of Animal Science Animal Science Journal (2017) ,  doi:10.1111/asj.12980