Molecular Typing And Pathogenicity Evaluation Of Poultry-origin Candida Isolates

Candidiasis is one of the most important poultry mycoses in China,but no systematic study was conducted to investigate the prevalence the Candida infection and pathogenicity of the isolates so far.In this study,153 yeast-like isolates were isolated from 235 avian samples collected from different avian species in southern Hebei Province.All birds were diagnosed as Candida infection based on clinical symptoms.These isolates were further identified by rDNA-ITS sequence analysis as Candida albicans(72/153),C.glabrata(43/153),C.tropiccalis(\0/153)and non-Candida yeast-like isolates(22/153).Subsequently,the objective Candida species gene specific and universe primer pairs were designed and a SYBR Green I based real-time PCR was developed for rapid diagnosis.The detection limit of pathogen genome is 101 copies·?L-1,with the sensitivity of 100-fold of the conventional PCR techbique.Using multilocus sequencing typing(MLST),the C.albicans isolates were clustered into 48 sequence types(STs),forming 5 individual groups and 10 sigleetons.They could also being assigned to type A(34/72),type B(15/72)and type C(23/72),respectively,by ABC typing.Statistical analysis with the chi-square independence test revealed that there were strong relationship between the molecular typing and host origin of these isolates.To investigate the pathogenicity of the C.albicans,representative isolate from each ST was chosen to infect chicks by oral or intravenous inoculation.Based on the scoring of clinical signs,survival and pathological lesions of infected birds,isolates of the three STs were considerd to be highly pathogenic to chicks by both infection routes.But the mortality rate 9.3%(7/75)for the crop infection was significantly lower than that 61.3%(46/75)of intravenous inoculation.As virulence-associated factors,the activities of secretory hydrolases of the representative isolates were detected,and significant differences were observed,The relationship between the hydrolase activity and virulence to mice was also analyzed.Collectively,our study presented for the first time the data for the prevalence of Candida infection in the avian species in Souhem Hebei.Our results also provided knowledge and technical support for further study on the pathogenesis of the avian candiasis.