Van Nederveen Viktoria, Johnson Yuliya Seldina, Ortega Ennzo, Soc Anthony, Smith Mark A, Melton-Celsa Angela R
Department of Microbiology and Immunology, Uniformed Services University, Bethesda, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, MD, USA.
Charles River Laboratories, Reno, NV, USA.
Microb Pathog. 2025 Jun;203:107444. doi: 10.1016/j.micpath.2025.107444. Epub 2025 Mar 1.
Enteroaggregative Escherichia coli (EAEC) are a diverse group of bacteria that cause diarrhea worldwide. EAEC significantly affect travelers to endemic regions, including military personnel, and children in developing countries where EAEC infection is associated with childhood failure-to-thrive. EAEC creates thick biofilms on the intestinal mucosa, a process that is thought to contribute to the development of both diarrhea and childhood failure-to-thrive. Typical EAEC strains encode and produce just one aggregative adherence fimbriae (AAF) out of the five different AAF types. The AAF are required for aggregative adherence to epithelial cells in vitro, but the degree of importance of each of the AAF types in both biofilm formation and pathogenesis is unknown. In this study, we investigated the role of the fimbriae in EAEC biofilms by deleting the major fimbrial subunit gene for the AAF from each of the five AAF categories and observing the impact on biofilm staining from recent EAEC clinical isolates. We found that biofilm was significantly reduced in all strains when the AAF gene was deleted, and that the defect could be overcome by complementation. In this work we also describe a modified murine EAEC model appropriate for colonization studies. In an antibiotic-treated mouse colonization model, some AAF mutant strains were attenuated for colonization, including AAF/II, AAF/IV, and AAF/V isolates. We did not observe complementation of the attenuated colonization phenotype in the mouse model. However, since we found a colonization defect for several EAEC mutant strains of different AAF types, a link between the fimbriae and colonization in the mice is supported. Taken together, our results show that the AAF are required for biofilm formation, and that some AAF contribute to colonization in a mouse model.
肠聚集性大肠杆菌（EAEC）是一类能在全球范围内引起腹泻的多种细菌。EAEC对前往流行地区的旅行者，包括军事人员，以及发展中国家的儿童有显著影响，在这些地区EAEC感染与儿童发育迟缓有关。EAEC在肠道黏膜上形成厚厚的生物膜，这一过程被认为与腹泻和儿童发育迟缓的发生都有关。典型的EAEC菌株在五种不同类型的聚集性黏附菌毛（AAF）中仅编码并产生一种。AAF是体外聚集黏附上皮细胞所必需的，但每种AAF类型在生物膜形成和发病机制中的重要程度尚不清楚。在本研究中，我们通过删除五种AAF类别中每种的AAF主要菌毛亚基基因，并观察对近期EAEC临床分离株生物膜染色的影响，来研究菌毛在EAEC生物膜中的作用。我们发现，当AAF基因被删除时，所有菌株的生物膜都显著减少，并且这种缺陷可以通过互补来克服。在这项工作中，我们还描述了一种适用于定植研究的改良小鼠EAEC模型。在抗生素处理的小鼠定植模型中，一些AAF突变菌株的定植能力减弱，包括AAF/II、AAF/IV和AAF/V分离株。我们在小鼠模型中未观察到减弱的定植表型的互补情况。然而，由于我们发现了几种不同AAF类型的EAEC突变菌株存在定植缺陷，因此支持了菌毛与小鼠定植之间的联系。综上所述，我们的结果表明AAF是生物膜形成所必需的，并且一些AAF有助于小鼠模型中的定植。
