某大型鸡场鸡大肠杆菌病流行病学调查

某大型鸡场的28个分场分离到的菌株，经生化检验为大肠杆菌的有87株，经O血清测定定型65株，4株自凝，18株未能定型，其中O78占20株，O1占14株，O2占5株，这些分离株中O78、O1、O2有39株占定型菌株的60．0％，因此可以认定O78、O1和O2为该大型鸡场的优势血清型，以不同场分离的菌株，以每分离株10^7菌落形成单位(CFU)细菌气管接种1日龄易感鸡，根据接种后7天内发生死亡和病变鸡的比例，确定出高致病株、中等致病株和低致病株分别为87．36％、8．05％和4．59％。

Epidemiological Investigation of Chicken Colibaciilosis on a Poultry farm

The purpose of this investigation was to characterize avian Eschserichia coli isolate s collected from one large farm.65out of87strains were identified as Escherichia coli isolates.Among E.coli.isolates,65strains were determined while18were not determined and4were self-aggu ltinated,which had20O 78 isolates,14O 1 isolates,5O 2 isolates,and these three isolates occupied60.0%among the65isolates.The relative pahtogenicity of serogroups Escherichia coli isolates from different factories was evaluated in susceptiable1-day-old chickens.Six birds were innoculated intratracheally with10 7 colony-forming unit(10 7 CPU)of E.coli.Based on mortality and lesions occurring during7-days period.The isolates were characterized as high,intermediate,and low pathogenicity respectively.The result suggested that87.36%are high pathogenetic,80.5%intermediate,4.59%low.