Antibiotic Changes Host Susceptibility to Eimeria falciformis Infection Associated with Alteration of Gut Microbiota.

Eimeria falciformis is a murine-infecting coccidium that mainly infects the cecum and colon where it coexists with a large number of endogenous bacteria. Here, we found that mice treated with a broad-spectrum antibiotic cocktail including ampicillin, neomycin, metronidazole, and vancomycin had less oocyst production and milder pathological consequences after infection than mice without antibiotics, regardless of the inoculation doses. Furthermore, we showed that antibiotic treatment reduced parasitic invasion and prolonged asexual stage during infection, which may result in alleviating the infection. Interestingly, when further defining different antibiotic combinations for infection, it was shown that mice treated with ampicillin plus vancomycin had substantially attenuated infections as measured by cecal parasite counts and histopathological features. In contrast, treatment with metronidazole plus neomycin was beneficial to infection. Analyses of gut microbiota revealed various changes in bacterial composition and diversity following antibiotic treatments that were associated with host susceptibility to infection. Together, these findings suggest that gut microbiota may regulate the course and pathogenicity of infection, while the mechanisms need to be further investigated, especially for the development of coccidial vaccines for use in farm animals.