The aggregate-forming pili (AFP) mediates the aggregative adherence of a hybrid-pathogenic <i>Escherichia coli</i> (UPEC/EAEC) isolated from a urinary tract infection

Enteroaggregative <i>Escherichia coli</i> (EAEC) comprises an important diarrheagenic pathotype, while uropathogenic <i>E. coli</i> (UPEC) is the most important agent of urinary tract infection (UTI). Recently, EAEC virulence factors have been detected in <i>E. coli</i> strains causing UTI, showing the importance of these hybrid-pathogenic strains. Previously, we detected an <i>E. coli</i> strain isolated from UTI (UPEC-46) presenting characteristics of EAEC, <i>e.g</i>., the aggregative adherence (AA) pattern and EAEC-associated genes (<i>aatA, aap</i>, and <i>pet</i>). In this current study, we analyzed the whole genomic sequence of UPEC-46 and characterized some phenotypic traits. The AA phenotype was observed in cell lineages of urinary and intestinal origin. The production of curli, cellulose, bacteriocins, and Pet toxin was detected. Additionally, UPEC-46 was not capable of forming biofilm using different culture media and human urine. The genome sequence analysis showed that this strain belongs to serotype O166:H12, ST10, and phylogroup A, harbors the <i>tet, aadA</i>, and <i>dfrA</i>/<i>sul</i> resistance genes, and is phylogenetically more related to EAEC strains isolated from human feces. UPEC-46 harbors three plasmids. Plasmid p46-1 (~135 kb) carries some EAEC marker genes and those encoding the aggregate-forming pili (AFP) and its regulator (<i>afpR</i>). A mutation in <i>afpA</i> (encoding the AFP major pilin) led to the loss of pilin production and assembly, and notably, a strongly reduced adhesion to epithelial cells. In summary, the genetic background and phenotypic traits analyzed suggest that UPEC-46 is a hybrid strain (UPEC/EAEC) and highlights the importance of AFP adhesin in the adherence to colorectal and bladder cell lines.肠聚集性大肠杆菌（Enteroaggregative *Escherichia coli*, EAEC）是一类重要的致腹泻致病型菌株，而尿路致病性大肠杆菌（Uropathogenic *E. coli*, UPEC）则是尿路感染（Urinary tract infection, UTI）最主要的致病菌。近期研究在引发尿路感染的大肠杆菌菌株中检出了EAEC毒力因子，凸显了这类双致病性杂交菌株的重要性。本团队此前曾从尿路感染患者样本中分离得到一株大肠杆菌UPEC-46，该菌株兼具EAEC相关特征，例如聚集性黏附（aggregative adherence, AA）表型以及EAEC相关毒力基因*aatA*、*aap*与*pet*。本研究对UPEC-46的全基因组序列展开分析，并对其部分表型特征进行了系统鉴定。结果显示，该菌株在泌尿与肠道来源的细胞系中均呈现聚集性黏附表型；可检测到卷曲菌毛、纤维素、细菌素及Pet毒素的合成与表达；但在多种不同培养基及人尿液环境中均无法形成生物膜。全基因组序列分析表明，UPEC-46隶属于血清型O166:H12、序列型ST10以及系统群A，携带*tet*、*aadA*以及*dfrA/sul*等耐药基因，且在系统发育层面与从人类粪便中分离的EAEC菌株亲缘关系更为接近。UPEC-46共携带3个质粒：其中质粒p46-1（约135 kb）携带部分EAEC特异性标记基因，以及编码聚集形成菌毛（aggregate-forming pili, AFP）及其调控蛋白AfpR的基因。对编码AFP主要菌毛蛋白的*afpA*基因进行突变后，菌株的菌毛蛋白合成与组装过程完全丧失，且其对上皮细胞的黏附能力显著降低。综上，本研究分析的遗传背景与表型特征均表明，UPEC-46是一株UPEC/EAEC杂交菌株，同时也凸显了AFP黏附素在结直肠与膀胱细胞系黏附过程中的关键作用。