肠道出血性大肠杆菌O157∶H7中肠道聚集粘附大肠杆菌耐热肠毒素1基因的检测

Detection of Enteroaggregative Escherichia coli Heat-Stable Enterotoxin 1 Gene in E.coli O157∶H7

应用聚合酶链式反应 ( polymerase chain reaction,PCR)对 1 99株肠道出血性大肠杆菌 ( enterohemor-rhagic Escherichia coli,EHEC) O1 57∶ H7中肠道聚集粘附大肠杆菌耐热肠毒素 1 ( enteroaggregative Es-cherichia coli heat-stable enterotoxin1 ,EAST1 )基因进行了检验。结果 ,从 1 % ( 2 / 1 99)菌株中检出了 EAST1基因。对其中 1株菌 ( EHEC O1 5796-84 )的 EAST1基因进行了序列测定。与以往发表的其他致腹泻性大肠杆菌的 EAST1基因的序列相比较 ,EHEC O1 5796-84与 EAgg EC ( O4 2 ,TL1 0 0和 1 60株 )、产肠毒素性大肠杆菌 ( enterotoxigenic E.coli,ETEC)、肠道致病性大肠杆菌 ( enteropathogenic E.coli,EPEC)、扩散粘附性大肠杆菌 ( diffusely adherening E.coli,DAEC)的 EAST1基因序列相同 ,但与 EAgg EC菌株 1 7-2的EAST1基因有 1个碱基对不同 ,从而导致 1个氨基酸残基的变化。本研究结果进一步表明 。

The presence of the enteroaggregative E.coli (EAggEC) heat stable enterotoxin 1 (EAST1) gene was investigated in 199 strains of enterohemorrhagic E.coli (EHEC) O157∶H7 by polymerase chain reaction (PCR). The EAST1 gene or its homologue was present in 2 (1%) of these strains. The EAST1 gene sequence of a positive strain 96 84 was determined by analyzing the PCR products on an automatic sequencer. Comparison of the EAST1 gene sequences analyzed in this study with those reported previously demonstrated that this E.coli O157∶H7 strain 96 84 shares a common sequence with EAggEC (strains O42, TL100 and 160), enteropathogenic E.coli (EPEC), diffusely adhering E.coli (type 1 DAEC), and enterotoxigenic E.coli (ETEC). But the EAST1 gene sequence of E.coli O157∶H7 strain 96 84 differs from that of EAggEC strain 17 2 by 1 base, resulting in a change in the deduced amino acid residue. This study further suggests that the EAST1 gene or its variant is a virulence gene widely existed among diarrheagenic E.coli.