Laboratorio de Patogénesis e Inmunología de Procesos Infecciosos, Instituto de Medicina Experimental (IMEX)-CONICET, Academia Nacional de Medicina, Buenos Aires, Argentina.
Division of Infection and Immunity, The Roslin Institute, University of Edinburgh, Easter Bush Campus, Edinburgh, EH25 9RG, U.K.
Clin Sci (Lond). 2020 Dec 23;134(24):3283-3301. doi: 10.1042/CS20200971.
Host adaptation of pathogens may increase intra- and interspecies transmission. We showed previously that the passage of a clinically isolated enterohemorrhagic Escherichia coli (EHEC) O157 strain (125/99) through the gastrointestinal tract of mice increases its pathogenicity in the same host. In this work, we aimed to elucidate the underlying mechanism(s) involved in the patho-adaptation of the stool-recovered (125RR) strain. We assessed the global transcription profile by microarray and found almost 100 differentially expressed genes in 125RR strain compared with 125/99 strain. We detected an overexpression of Type Three Secretion System (TTSS) proteins at the mRNA and protein levels and demonstrated increased adhesion to epithelial cell lines for the 125RR strain. Additional key attributes of the 125RR strain were: increased motility on semisolid agar, which correlated with an increased fliC mRNA level; reduced Stx2 production at the mRNA and protein levels; increased survival at pH 2.5, as determined by acid resistance assays. We tested whether the overexpression of the LEE-encoded regulator (ler) in trans in the 125/99 strain could recreate the increased pathogenicity observed in the 125RR strain. As anticipated ler overexpression led to increased expression of TTSS proteins and bacterial adhesion to epithelial cells in vitro but also increased mortality and intestinal colonization in vivo. We conclude that this host-adaptation process required changes in several mechanisms that improved EHEC O157 fitness in the new host. The research highlights some of the bacterial mechanisms required for horizontal transmission of these zoonotic pathogens between their animal and human populations.
病原体的宿主适应性可能会增加种内和种间传播。我们之前曾表明，通过胃肠道传递临床分离的肠出血性大肠杆菌（EHEC）O157 菌株（125/99）会增加其在同一宿主中的致病性。在这项工作中，我们旨在阐明粪便回收（125RR）菌株适应病原体的潜在机制。我们通过微阵列评估了全球转录谱，发现与 125/99 菌株相比，125RR 菌株中几乎有 100 个差异表达基因。我们在 mRNA 和蛋白质水平上检测到 III 型分泌系统（TTSS）蛋白的过度表达，并证明 125RR 菌株对上皮细胞系的粘附性增加。125RR 菌株的其他关键属性包括：在半固体琼脂上的运动性增加，这与 fliC mRNA 水平的增加相关；在 mRNA 和蛋白质水平上 Stx2 产量降低；在 pH 2.5 下的生存能力增加，通过耐酸测定来确定。我们测试了在 125/99 菌株中转录过表达 LEE 编码的调节因子（ler）是否可以重现 125RR 菌株中观察到的增加的致病性。正如预期的那样，ler 过表达导致 TTSS 蛋白的过度表达和细菌体外粘附上皮细胞，但也导致体内死亡率和肠道定植增加。我们得出结论，这种宿主适应过程需要改变几种机制，这些机制提高了 EHEC O157 在新宿主中的适应性。该研究强调了这些人畜共患病病原体在其动物和人群之间进行水平传播所需的一些细菌机制。
