PDF(Pubmed)
Abstract：
Escherichia fergusonii strains have been isolated from patients with diarrhea, but their virulence determinant has not been well elucidated. Here, we report the first isolation of a heat-labile enterotoxin 1 (LT1)-producing E. fergusonii strain (strain 30038) from a patient in Japan. The complete genome sequence of strain 30038 was determined and subjected to comparative genomics and phylogenetic analyses with 195 publicly available genomes of E. fergusonii. In addition to strain 30038, the elt1 gene was also identified in an E. fergusonii strain that is phylogenetically distinct and which was isolated from poultry in the United Kingdom. Fine genomic comparison revealed that these two strains share comparable elt1-bearing plasmids. However, an intriguing distinction arises in strain 30038, wherein the plasmid has integrated into the chromosome via a recombination process mediated by an insertion sequence. The production of active LT1 toxin by strain 30038 was verified through an in vitro assay using cultured cells. A large plasmid carrying 11 antimicrobial resistance genes was also identified in strain 30038. Our results indicate that extensive surveillance of elt1-positive E. fergusonii strains as diarrheagenic pathogens is needed. IMPORTANCE Escherichia fergusonii, a species closely related to Escherichia coli, is known to cause sporadic conditions in humans, including diarrhea. However, the critical virulence factors in E. fergusonii clinical isolates remain to be identified. This study shows the first isolation of an E. fergusonii strain carrying the elt1 gene, which encodes heat-labile enterotoxin 1, from a patient with diarrhea. Our analysis of public databases also revealed the presence of elt1-positive E. fergusonii strains isolated from poultry in the United Kingdom. Interestingly, while the elt1 gene in the poultry isolate was present on a large plasmid, in the human isolate it was integrated into the chromosome, which may confer stability on the elt1-carrying genetic element. Our findings highlight the need for extensive surveillance of elt1-positive E. fergusonii strains in livestock animals.
摘要：
已经从腹泻患者中分离出了大肠杆菌菌株，但是它们的毒力决定因素还没有得到很好的阐明。这里,我们报道了首次从日本患者中分离出产生热不稳定肠毒素1（LT1）的E.Fergusonii菌株（菌株30038）。确定菌株30038的完整基因组序列,并使用195个公开可用的E.fergusonii基因组进行比较基因组学和系统发育分析。除了菌株30038之外,还在系统发生上不同的并且从英国的家禽中分离的E.ergusonii菌株中鉴定了elt1基因。精细的基因组比较显示，这两个菌株共享可比较的携带elt1的质粒。然而,一个有趣的区别出现在菌株30038中，其中质粒已通过插入序列介导的重组过程整合到染色体中。通过使用培养细胞的体外测定来验证菌株30038对活性LT1毒素的产生。还在菌株30038中鉴定了携带11个抗微生物抗性基因的大质粒。我们的结果表明，需要对作为腹泻病原体的elt1阳性E.fergusonii菌株进行广泛的监测。重要性大肠杆菌，与大肠杆菌密切相关的物种，已知会导致人类的零星状况，包括腹泻.然而,临床分离株中的关键毒力因子仍有待鉴定。这项研究显示了携带elt1基因的E.fergusonii菌株的首次分离，它编码来自腹泻患者的不耐热肠毒素1。我们对公共数据库的分析还显示，存在从英国家禽中分离出的elt1阳性E.Fergusonii菌株。有趣的是,虽然家禽分离物中的elt1基因存在于一个大质粒上，在人类分离物中，它被整合到染色体中，这可能赋予携带elt1的遗传元件稳定性。我们的发现强调了对家畜动物中elt1阳性E.Fergusonii菌株进行广泛监测的必要性。
