Cyniclomyces guttulatus is an opportunistic pathogen in rabbits with coccidiosis
Abstract Background: Cyniclomyces guttulatus is a common inhabitant of the gastrointestinal tract in rabbits, and large numbers are often present in feces of diarrheic rabbits. However, its relation with rabbit diarrhea has not been clearly identified. Relationship between C. guttulatus and the rabbit are identified in this paper.Methods: YPG (pH 1.5) medium and 96-well culture plate were used to isolate C. guttulatus from rabbit. Automatic microbial growth curve analyser and optical density scanner were used to optimized culture conditions of the C. guttulatus strain in the YPG medium. Microscope observation, PCR and gene sequencing were used to identify the C. guttulatus strain. Animal inoculation with the C. guttulatus strain or co-inoculation with E. intestinalis were used identify relationship between C. guttulatus and the rabbit. Results: A C. guttulatus Zhejiang strain was isolated from a rabbit with diarrhea and the culture conditions in YPG medium were optimized. The sequenced 18S and 26S ribosomal DNA fragments were 1559bp and 632bp, respectively, and showed 99.8% homology with the 18S ribosomal sequence of the NRRL Y-17561 isolate from the dog and 100% homology with the 26S ribosomal sequence of the DPA-CGR1 and CGDPA-GP1 isolates from the rabbit and guinea pig. Our isolate was not pathogenic to healthy SPF rabbits. Instead, rabbits inoculated with the yeast had a slightly better body weight gain and higher food intake. Rabbits co-inoculated with C. guttulatus and the coccidian, E. intestinalis developed more severe coccidiosis as shown by clinical signs, and decreased body weight gain, diarrhea and death, associated with significantly higher fecal output of C. guttulatus vegetative cells but lower coccidian oocysts output than the rabbits inoculated with C. guttulatus or E. intestinalis alone. We also surveyed the prevalence of C. guttulatus in rabbits and found a positive rate of 83% in Zhejiang province. Conclusions: Our results indicate that C. guttulatus alone is not pathogenic to healthy rabbits and seems a probiotic microorganism in rabbits, but could become an opportunistic pathogen when the digestive tract is damaged by other pathogens such as coccidia.