Haemolysin E- and enterohaemolysin-derived haemolytic activity of O55/O157 strains and other Escherichia coli lineages.
Haemolysin E- and enterohaemolysin-derived haemolytic activity of O55/O157 strains and other Escherichia coli lineages.
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DOI：
10.1099/mic.0.054775-0
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发表时间：
2012-03
期刊：
影响因子：
1.5
通讯作者：
K. Murase;Tadasuke Ooka;Atsushi Iguchi;Yoshitoshi Ogura;K. Nakayama;M. Asadulghani;Md. Rakibul Islam;Hirotaka Hiyoshi;T. Kodama;L. Beutin;Tetsuya Hayashi
中科院分区：
文献类型：
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作者：
K. Murase;Tadasuke Ooka;Atsushi Iguchi;Yoshitoshi Ogura;K. Nakayama;M. Asadulghani;Md. Rakibul Islam;Hirotaka Hiyoshi;T. Kodama;L. Beutin;Tetsuya Hayashi
迄今为止在大肠杆菌中鉴定的三种溶血素中，α-溶血素（HlyA）是在肠外致病菌株的致病岛上编码的，而肠溶血素（EhxA）是在肠出血性大肠杆菌（EHEC）菌株的毒力质粒上编码的。相比之下，溶血素 E (HlyE) 基因位于大肠杆菌染色体主链上，因此广泛分布于大肠杆菌菌株中。然而，由于 hlyE 基因表达受到 H-NS 蛋白的抑制，并且该基因在许多菌株中已被破坏，因此通过血琼脂平板上的常规筛选无法检测到其溶血活性。在这项研究中，我们发现，在用于检测 EhxA 产生的洗涤血琼脂平板（EHX 平板）上厌氧培养后，可以检测到肠病性大肠杆菌 (EPEC) O55 : H7 的 HlyE 衍生溶血活性。我们还发现，在有氧和厌氧生长条件下在EHX平板上观察到的EHEC O157：H7的溶血活性分别源自EhxA和HlyE；两种溶血素的这种差异表达发生在转录水平。我们对 60 种不同致病型和系统发育的大肠杆菌菌株的溶血素基因库、溶血表型和 hlyE 基因序列进行了分析，结果表明，如果基因完整，在厌氧生长条件下，通常可以在 EHX 平板上检测到 HlyE 活性。此外，我们的结果表明 hlyE 基因失活发生在五个大肠杆菌谱系中的三个（系统群 A、B1 和 B2），这表明了系统群特异性基因破坏模式。
Among three haemolysins identified thus far in Escherichia coli, alpha-haemolysin (HlyA) is encoded on the pathogenicity islands of extraintestinal pathogenic strains, while enterohaemolysin (EhxA) is encoded on the virulence plasmids of enterohaemorrhagic E. coli (EHEC) strains. In contrast, the gene for haemolysin E (HlyE) is located on the E. coli chromosome backbone and is therefore widely distributed among E. coli strains. However, because hlyE gene expression is repressed by the H-NS protein and because the gene has been disrupted in many strains, its haemolytic activity cannot be detected in wild-type strains by routine screening on blood agar plates. In this study, we found that the HlyE-derived haemolytic activity of enteropathogenic E. coli (EPEC) O55 : H7 can be detected after anaerobic cultivation on a washed blood agar plate (EHX plate) that is used to detect the production of EhxA. We also found that the haemolytic activity of EHEC O157 : H7 observed on EHX plates under aerobic and anaerobic growth conditions is derived from EhxA and HlyE, respectively; this differential expression of the two haemolysins occurs at the transcriptional level. Our analysis of 60 E. coli strains of various pathotypes and phylogenies for their repertoires of haemolysin genes, haemolytic phenotypes and hlyE gene sequences revealed that HlyE activity can generally be detected on EHX plates under anaerobic growth conditions if the gene is intact. Furthermore, our results indicate that hlyE gene inactivation occurred in three of the five E. coli lineages (phylogroups A, B1 and B2), which demonstrates phylogroup-specific gene disruption patterns.