Prevalence and characterization of Clostridium perfringens isolated from different chicken farms in China.

Clostridium perfringens (C. perfringens) is a common pathogenic microorganism present in nature, which can cause animal and human diseases, such as necrotizing enteritis (NE) in poultry. Little is known about the current prevalence status of C. perfringens from poultry farms of different types and regions in China. From December 2018 to August 2019, we investigated the prevalence, genotype distribution and drug resistance of C. perfringens from Guangdong, Pingyin, Tai'an and Weifang. A total of 622 samples were collected and processed for C. perfringens isolation, among which 239 (38.42%) samples were determined to be positive for C. perfringens. A total of 312 isolates of C. perfringens were recovered (1-5 strains were isolated for each positive sample), and 98.72% of the isolates were identified as type A, while the others were type F. Antimicrobial susceptibility testing revealed that 47.71% of the isolates were resistant to at least five classes of commonly used antibiotics. Multilocus sequence typing (MLST) showed that 74 representative isolates were divided into 63 sequence types (STs), and the Simpson's diversity index (Ds) of the STs for the five farms was 0.9799. 37.84% of the isolates were classified into seven clonal complexes (CC1-CC7), and the isolates from the same farm were more concentrated in the minimum spanning tree. In addition, some cloaca isolates and feed isolates were distributed in the same ST or CC; this result indicates that the C. perfringens in chicken can come from the environment (feed etc.).