Department of Microbiology and Immunology, Medical College of Wisconsingrid.30760.32, Milwaukee, Wisconsin, USA.
Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsingrid.30760.32, Milwaukee, Wisconsin, USA.
Microbiol Spectr. 2022 Aug 31;10(4):e0208322. doi: 10.1128/spectrum.02083-22. Epub 2022 Jul 20.
Achromobacter xylosoxidans is an opportunistic pathogen implicated in a wide variety of human infections including the ability to colonize the lungs of cystic fibrosis (CF) patients. The role of A. xylosoxidans in human pathology remains controversial due to the lack of optimized and model systems to identify and test bacterial gene products that promote a pathological response. We have previously identified macrophages as a target host cell for A. xylosoxidans-induced cytotoxicity. By optimizing our macrophage infection model, we determined that A. xylosoxidans enters macrophages and can reside within a membrane bound vacuole for extended periods of time. Intracellular replication appears limited with cellular lysis preceding an enhanced, mainly extracellular replication cycle. Using our optimized model system along with transposon mutagenesis, we identified 163 genes that contribute to macrophage cytotoxicity. From this list, we characterized a giant RTX adhesin encoded downstream of a type one secretion system (T1SS) that mediates bacterial binding and entry into host macrophages, an important first step toward cellular toxicity and inflammation. The RTX adhesin is encoded by other human isolates and is recognized by antibodies present in serum isolated from CF patients colonized by A. xylosoxidans, indicating this virulence factor is produced and deployed . This study represents the first characterization of A. xylosoxidans replication during infection and identifies a variety of genes that may be linked to virulence and human pathology. Patients affected by CF develop chronic bacterial infections characterized by inflammatory exacerbations and tissue damage. Advancements in sequencing technologies have broadened the list of opportunistic pathogens colonizing the CF lung. A. xylosoxidans is increasingly recognized as an opportunistic pathogen in CF, yet our understanding of the bacterium as a contributor to human disease is limited. Genomic studies have identified potential virulence determinants in A. xylosoxidans isolates, but few have been mechanistically studied. Using our optimized cell model, we identified and characterized a bacterial adhesin that mediates binding and uptake by host macrophages leading to cytotoxicity. A subset of serum samples from CF patients contains antibodies that recognize the RTX adhesion, suggesting, for the first time, that this virulence determinant is produced . This work furthers our understanding of A. xylosoxidans virulence factors at a mechanistic level.
木糖氧化无色杆菌是一种机会性病原体，与多种人类感染有关，包括能够定植囊性纤维化 (CF) 患者的肺部。由于缺乏优化的 和 模型系统来识别和测试促进病理反应的细菌基因产物，因此木糖氧化无色杆菌在人类病理学中的作用仍存在争议。我们之前已经确定巨噬细胞是木糖氧化无色杆菌诱导细胞毒性的靶宿主细胞。通过优化我们的巨噬细胞感染模型，我们确定木糖氧化无色杆菌进入巨噬细胞，并可以在膜结合的空泡中长时间存在。细胞内复制似乎受到限制，细胞裂解前有一个增强的、主要是细胞外复制周期。使用我们优化的 模型系统和转座子诱变，我们确定了 163 个基因有助于巨噬细胞细胞毒性。从这个列表中，我们鉴定了一个位于 I 型分泌系统 (T1SS) 下游的巨型 RTX 粘附素，该粘附素介导细菌结合和进入宿主巨噬细胞，这是细胞毒性和炎症的重要第一步。RTX 粘附素由其他人类分离株编码，并被从定植有木糖氧化无色杆菌的 CF 患者血清中分离的抗体识别，表明这种毒力因子被产生和部署。这项研究代表了木糖氧化无色杆菌感染期间复制的首次表征，并确定了多种可能与毒力和人类病理学相关的基因。 受 CF 影响的患者会发展为慢性细菌感染，其特征为炎症加重和组织损伤。测序技术的进步拓宽了定植在 CF 肺部的机会性病原体的名单。木糖氧化无色杆菌在 CF 中越来越被认为是一种机会性病原体，但我们对该细菌作为人类疾病的贡献的理解是有限的。基因组研究已经确定了木糖氧化无色杆菌分离株中的潜在毒力决定因素，但很少有对其进行机制研究。使用我们优化的 细胞模型，我们鉴定并表征了一种介导与宿主巨噬细胞结合和摄取的细菌粘附素，导致细胞毒性。来自 CF 患者的一部分血清样本含有识别 RTX 粘附素的抗体，这首次表明该毒力决定因素被产生。这项工作在机制水平上进一步加深了我们对木糖氧化无色杆菌毒力因子的理解。
