Department of Microbiology and Immunology, Wake Forest University Health Sciences, 5053 Hanes Building, 1000 Medical Center Boulevard, Winston-Salem, NC 27157, USA.
Infect Immun. 2011 Jan;79(1):431-8. doi: 10.1128/IAI.00660-10. Epub 2010 Oct 18.
Nontypeable Haemophilus influenzae (NTHI) is a leading cause of otitis media infections, which are often chronic and/or recurrent in nature. NTHI and other bacterial species persist in vivo within biofilms during otitis media and other persistent infections. These biofilms have a significant host component that includes neutrophil extracellular traps (NETs). These NETs do not mediate clearance of NTHI, which survives within NET structures by means of specific subpopulations of lipooligosaccharides on the bacterial surface that are determinants of biofilm formation in vitro. In this study, the ability of NTHI and NTHI components to initiate NET formation was examined using an in vitro model system. Both viable and nonviable NTHI strains were shown to promote NET formation, as did preparations of bacterial DNA, outer membrane proteins, and lipooligosaccharide (endotoxin). However, only endotoxin from a parental strain of NTHI exhibited equivalent potency in NET formation to that of NTHI. Additional studies showed that NTHI entrapped within NET structures is resistant to both extracellular killing within NETs and phagocytic killing by incoming neutrophils, due to oligosaccharide moieties within the lipooligosaccharides. Thus, we concluded that NTHI elicits NET formation by means of multiple pathogen-associated molecular patterns (most notably endotoxin) and is highly resistant to killing within NET structures. These data support the conclusion that, for NTHI, formation of NET structures may be a persistence determinant by providing a niche within the middle-ear chamber.
无乳链球菌（NTHI）是中耳炎感染的主要原因，这种感染通常具有慢性和/或复发性。NTHI 和其他细菌物种在中耳炎和其他持续性感染期间在体内生物膜中持续存在。这些生物膜具有重要的宿主成分，包括中性粒细胞胞外陷阱（NETs）。这些 NET 并不能清除 NTHI，NTHI 可以通过细菌表面特定的脂寡糖亚群在 NET 结构内存活，这些脂寡糖亚群是体外生物膜形成的决定因素。在这项研究中，使用体外模型系统研究了 NTHI 和 NTHI 成分引发 NET 形成的能力。结果表明，无论是活菌还是死菌 NTHI 株都能促进 NET 形成，细菌 DNA、外膜蛋白和脂寡糖（内毒素）制剂也是如此。然而，只有 NTHI 亲本菌株的内毒素在 NET 形成中的效力与 NTHI 相当。进一步的研究表明，NTHI 被困在 NET 结构内，由于脂寡糖中的寡糖部分，对 NET 内的细胞外杀伤和进入的中性粒细胞的吞噬杀伤均具有抗性。因此，我们得出结论，NTHI 通过多种病原体相关分子模式（最显著的是内毒素）引发 NET 形成，并且在 NET 结构内具有高度的杀伤抗性。这些数据支持这样的结论，即对于 NTHI 而言，NET 结构的形成可能是一种持久性决定因素，因为它在中耳腔内提供了一个小生境。
