Genetyping Analysis Of Clostridium Perfringens Strains Isolated From Broiler Chickens In Sourthern China

Clostridium perfringens is the causative agent of avian necrotic enteritis,which is frequently induced by the infection of Eimeria spp.,or by the administration of Eimeria live attenuated oocyst vaccines.This disease is characterized by the necrosis of intestinal mucosa epithelial cells and threatens the poultry industry worldwide.The risk of this disease,due to the obligatory addition of antibacterial and anticoccidiosis drugs,and the extensive use of wheat in diets,has increased in recent years.Recent reports demonstrated that the genetic characteristics were diverse among the strains isolated from NE chickens and healthy individuals,and between different areas.The results also suggested a close correlation between pathogenicity and genetic background.In this study,we collected diarrhoea or bloody faeces and intestine samples from NE chickens and healthy individuals from different areas to identify the toxin genes.We next investigated the drug resistances of C.perfringens isolates.Pulsed field gel electrophoresis(PFGE)analysis was also conducted to evaluate the genetic diversity.These results represent a primary and significant step in understanding the epidemic characters of C.perfringens in southern china,and fundamental data sets for the disease control.1.Among 692 samples collected from 17 districts of 7 provinces,we isolated 214 C perfringens strains,including 206 type A and 8 type C strains.PCR detection specific to ?2 toxin gene found that the rate of ?2-positive strains was 41%(87 of 214),whereas the rate of netB-positive strains was 2.3%(5 of 214).The MIC(Minimum Inhibitory Concentration)results indicated that nosiheptide has good antibacterial effect on all strains,the strains isolated from Deyang Sichuan(2013),Meishan Sichuan(2013)and Heshan Guangdong(2013)exhibited sensitive to 11 drugs,however,Guangxi Guilin(2014)Strains only show sensitivity to nosiheptide.2.By the using PFGE method,we analyzed 108 C.perfringens strains to classify their genetic background.Strains with 75%similarity will be grouped into one genetic cluster,and 99%similarity means same genotype.The results indicated that all the 108 stains were grouped into 15 clusters and 80 genotypes.The genetic relationship of the strains is correlated to geographic location,but irrelevant to stain toxin types.The healthy chicken carried several different C.perfringens clones both within a flock and even individual birds,whereas flocks suffering from NE or cholangio-hepatitis carry only one or two clones.