Borst Luke B, Suyemoto M Mitsu, Scholl Elizabeth H, Fuller Fredrick J, Barnes H John
Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America.
Bioinformatics Consulting and Service Core, Bioinformatics Research Center, College of Agriculture and Life Sciences, College of Sciences, North Carolina State University, Raleigh, North Carolina, United States of America.
PLoS One. 2015 Apr 10;10(4):e0121294. doi: 10.1371/journal.pone.0121294. eCollection 2015.
Enterococcus cecorum (EC) is the dominant enteric commensal of adult chickens and contributes to the gut consortia of many avian and mammalian species. While EC infection is an uncommon zoonosis, like other enterococcal species it can cause life-threating nosocomial infection in people. In contrast to other enterococci which are considered opportunistic pathogens, emerging pathogenic strains of EC cause outbreaks of musculoskeletal disease in broiler chickens. Typical morbidity and mortality is comparable to other important infectious diseases of poultry. In molecular epidemiologic studies, pathogenic EC strains were found to be genetically clonal. These findings suggested acquisition of specific virulence determinants by pathogenic EC. To identify divergent genomic features and acquired virulence determinants in pathogenic EC; comparative genomic analysis was performed on genomes of 3 pathogenic and 3 commensal strains of EC. Pathogenic isolates had smaller genomes with a higher GC content, and they demonstrated large regions of synteny compared to commensal isolates. A molecular phylogenetic analysis demonstrated sequence divergence in pathogenic EC genomes. At a threshold of 98% identity, 414 predicted proteins were identified that were highly conserved in pathogenic EC but not in commensal EC. Among these, divergent CRISPR-cas defense loci were observed. In commensal EC, the type IIA arrangement typical for enterococci was present; however, pathogenic EC had a type IC locus, which is novel in enterococci but commonly observed in streptococci. Potential mediators of virulence identified in this analysis included a polysaccharide capsular locus similar to that recently described for E. faecium, an epa-like locus, and cell wall associated proteins which may bind host extracellular matrix. This analysis identified specific genomic regions, coding sequences, and predicted proteins which may be related to the divergent evolution and increased virulence of emerging pathogenic strains of EC.
盲肠肠球菌（EC）是成年鸡肠道中的优势共生菌，并存在于许多禽类和哺乳动物的肠道菌群中。虽然EC感染是一种不常见的人畜共患病，但与其他肠球菌属物种一样，它可在人群中引起危及生命的医院感染。与被认为是机会性病原体的其他肠球菌不同，新兴的致病性EC菌株可导致肉鸡发生肌肉骨骼疾病暴发。其典型的发病率和死亡率与家禽的其他重要传染病相当。在分子流行病学研究中，发现致病性EC菌株具有基因克隆性。这些发现表明致病性EC获得了特定的毒力决定因素。为了鉴定致病性EC中不同的基因组特征和获得的毒力决定因素，对3株致病性EC菌株和3株共生EC菌株的基因组进行了比较基因组分析。致病性分离株的基因组较小，GC含量较高，与共生分离株相比，它们显示出大片的同线性区域。分子系统发育分析表明致病性EC基因组存在序列差异。在98%的同一性阈值下，鉴定出414种预测蛋白，这些蛋白在致病性EC中高度保守，但在共生EC中不保守。其中，观察到不同的CRISPR-cas防御位点。在共生EC中，存在肠球菌典型的IIA型排列；然而，致病性EC有一个IC型位点，这在肠球菌中是新发现的，但在链球菌中常见。该分析中鉴定出的潜在毒力介质包括一个类似于最近描述的粪肠球菌的多糖荚膜位点、一个类epa位点以及可能结合宿主细胞外基质的细胞壁相关蛋白。该分析确定了可能与新兴致病性EC菌株的分化进化和毒力增加相关的特定基因组区域、编码序列和预测蛋白。
