Isolation and identification of Pasteurella from Fowl cholera and the study of its pathogenicity

Avian pasteurellosis,also known as fowl cholera,is a hemorrhagic,septic infectious disease of chickens,turkeys,ducks,geese and other birds caused by Pasteurella multocida.Avian pasteurella disease occured severely in chicken farms in some areas of China,which often caused serious economic losses,and it is one of the major infectious diseases that harms the poultry industry.In October 2011,a chicken farm in Guangxi province was found to have laying hens acute fatal cases,the results of the epidemiological survey and clinical necropsy suspected that the disease may be caused by avian Pasteurella infection.The microscopic examination of isolated pathogen showed that it was a kind of small Gram negative bacilli,with bipolar staining on Wright′s stain.16S rRNA sequence analysis showed that this strain shared 98% homology with avian Pasteurella multocida.Genotyping by PCR identified it as serogroup A Pasteurella multocida.The result of pathogenicity testing showed that the isolated bacteria had a high pathogenicity on chickens,and artificially infected with 100 CFU could lead to the death of a 10-week-old healthy chickens within three days.The result of susceptibility testing showed that the isolated bacteria was sensitive to ciprofloxacin,enrofloxacin,tetracycline,furazolidone and ofloxacin.By thorough disinfection of the chicken farms and with the use of enrofloxacin and tetracycline treatment,further occurrence of the disease was finally controlled.