Maurer J J, Brown T P, Steffens W L, Thayer S G
Department of Avian Medicine, College of Veterinary Medicine, University of Georgia, Athens 30602-4875, USA.
Avian Dis. 1998 Jan-Mar;42(1):106-18.
Escherichia coli establishes a secondary respiratory tract infection in birds following inhalation of contaminated dust and litter particles. Escherichia coli express adhesins under conditions reflective of the ambient temperatures present in poultry houses. These microbial adhesins allow E. coli to attach to cell types that it initially encounters in the respiratory tract. Ambient temperature-regulated adhesins represent a new class of bacterial hemagglutinins that include pili and the thin, aggregative, flexible filaments known as "curli." This study examines the occurrence of the ambient temperature-regulated adhesins, curli (crl, csgA), and an avian-specific, temperature-sensitive hemagglutinin, tsh, among avian and mammalian E. coli isolates. The avian hemagglutinin gene tsh was present in approximately 46% of clinical avian E. coli isolates. This gene was not detected among commensal E. coli isolated from healthy broiler chickens. Unlike tsh, curli genes were ubiquitous among E. coli. However, curli were observed in only half of the avian E. coli examined by electron microscopy. Curli were not present among several nonavian E. coli positive for crl and csgA. Approximately 25% of avian E. coli isolates agglutinated chicken erythrocytes when bacteria were grown at room temperature. Hemagglutination was not specific to E. coli isolated from poultry. Presence of either tsh or curli genes was not indicative of an isolate's ability to agglutinate chicken red blood cells. No discernible structures were observed mediating attachment of the bacteria to chicken red blood cells. An additional avian-specific hemagglutinin appears to be present among avian E. coli.
大肠杆菌在吸入受污染的灰尘和垫料颗粒后会在禽类中引发继发性呼吸道感染。大肠杆菌在反映禽舍环境温度的条件下表达粘附素。这些微生物粘附素使大肠杆菌能够附着于呼吸道中最初遇到的细胞类型。环境温度调节的粘附素代表了一类新的细菌血凝素，包括菌毛和称为“卷曲菌毛”的细、聚集、柔性细丝。本研究调查了禽源和哺乳动物源大肠杆菌分离株中环境温度调节的粘附素卷曲菌毛（crl、csgA）以及一种禽特异性、温度敏感血凝素tsh的出现情况。禽血凝素基因tsh存在于约46%的临床禽源大肠杆菌分离株中。从健康肉鸡分离的共生大肠杆菌中未检测到该基因。与tsh不同，卷曲菌毛基因在大肠杆菌中普遍存在。然而，通过电子显微镜检查，仅在一半的禽源大肠杆菌中观察到卷曲菌毛。在几种crl和csgA呈阳性的非禽源大肠杆菌中未发现卷曲菌毛。当细菌在室温下生长时，约25%的禽源大肠杆菌分离株凝集鸡红细胞。血凝作用并非禽源大肠杆菌所特有。tsh或卷曲菌毛基因的存在并不表明分离株凝集鸡红细胞的能力。未观察到介导细菌与鸡红细胞附着的可识别结构。禽源大肠杆菌中似乎还存在另一种禽特异性血凝素。
