ABSTRACT

The H30Rx subclade of Escherichia coli ST131 is a clinically important, globally dispersed pathogenic lineage that typically displays resistance to fluoroquinolones and extended spectrum β-lactams. Isolates EC233 and EC234, variants of ST131-H30Rx with a novel sequence type (ST) 8196, isolated from unrelated patients presenting with bacteraemia at a Sydney Hospital in 2014 are characterised here. EC233 and EC234 are phylogroup B2, serotype O25:H4A, and resistant to ampicillin, amoxicillin, cefoxitin, ceftazidime, ceftriaxone, ciprofloxacin, norfloxacin and gentamicin and are likely clonal. Both harbour an IncFII_2 plasmid (pSPRC_Ec234-FII) that carries most of the resistance genes on an IS26 associated translocatable unit, two small plasmids and a novel IncI1 plasmid (pSPRC_Ec234-I). SNP-based phylogenetic analysis of the core genome of representatives within the ST131 clonal complex places both isolates in a subclade with three clinical Australian ST131-H30Rx clade-C isolates. A MrBayes phylogeny analysis of EC233 and EC234 indicates ST8196 share a most recent common ancestor with ST131-H30Rx strain EC70 isolated from the same hospital in 2013. Our study identified genomic hallmarks that define the ST131-H30Rx subclade in the ST8196 isolates and highlights a need for unbiased genomic surveillance approaches to identify novel high-risk MDR E. coli pathogens that impact healthcare facilities.

摘要

大肠杆菌ST131的H 30Rx子群是临床上重要的，全球分布的病原体谱系，通常对氟喹诺酮类和广谱β-内酰胺类具有抗性。本文对2014年在悉尼医院从患有细菌血症的无关患者中分离到的具有新序列类型（ST）8196的ST131- H 30Rx变体EC233和EC234进行了表征。EC233和EC234是phylogroup B2，血清型O25：H 4A，对氨苄西林，阿莫西林，头孢西丁，头孢他啶，头孢曲松，环丙沙星，诺氟沙星和庆大霉素具有抗性，可能是克隆的。两者都带有一个IncFII_2质粒（pSPRC_Ec234-FII），该质粒携带IS 26上的大多数抗性基因相关的易位单元，两个小质粒和一个新的IncI1质粒（pSPRC_Ec234-I）。对ST131克隆复合体内代表的核心基因组进行基于SNP的系统发育分析，将这两个分离株与三个澳大利亚临床ST131- H 30Rx进化枝C分离株置于一个亚小笼中。MrBayes对EC233和EC234进行的系统发育分析表明，ST8196与2013年从同一家医院分离的ST131- H 30Rx菌株EC70具有最新的共同祖先。我们的研究确定了定义ST8196分离株中ST131- H 30Rx子代的基因组标志，并突出显示了需要使用无偏见的基因组监测方法来鉴定影响医疗机构的新型高风险MDR大肠杆菌病原体。