Division of Experimental Infection Medicine, Department of Translational Medicine, Lund University, Malmö, Sweden.
Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden.
Infect Immun. 2020 Sep 18;88(10). doi: 10.1128/IAI.00133-20.
Biofilm formation by (group A streptococcus [GAS]) in model systems mimicking the respiratory tract is poorly documented. Most studies have been conducted on abiotic surfaces, which poorly represent human tissues. We have previously shown that GAS forms mature and antibiotic-resistant biofilms on physiologically relevant epithelial cells. However, the roles of the substratum, extracellular matrix (ECM) components, and GAS virulence factors in biofilm formation and structure are unclear. In this study, biofilm formation was measured on respiratory epithelial cells and keratinocytes by determining biomass and antibiotic resistance, and biofilm morphology was visualized using scanning electron microscopy. All GAS isolates tested formed biofilms that had similar, albeit not identical, biomass and antibiotic resistance for both cell types. Interestingly, functionally mature biofilms formed more rapidly on keratinocytes but were structurally denser and coated with more ECM on respiratory epithelial cells. The ECM was crucial for biofilm integrity, as protein- and DNA-degrading enzymes induced bacterial release from biofilms. Abiotic surfaces supported biofilm formation, but these biofilms were structurally less dense and organized. No major role for M protein, capsule, or streptolysin O was observed in biofilm formation on epithelial cells, although some morphological differences were detected. NAD-glycohydrolase was required for optimal biofilm formation, whereas streptolysin S and cysteine protease SpeB impaired this process. Finally, no correlation was found between cell adherence or autoaggregation and GAS biofilm formation. Combined, these results provide a better understanding of the role of biofilm formation in GAS pathogenesis and can potentially provide novel targets for future treatments against GAS infections.
生物膜形成 （A 组链球菌[GAS]） 在模拟呼吸道的模型系统中形成的情况记录不佳。大多数研究都是在非生物表面进行的，这些表面不能很好地代表人体组织。我们之前已经表明，GAS 在生理相关的上皮细胞上形成成熟和抗抗生素的生物膜。然而，基质、细胞外基质（ECM）成分和 GAS 毒力因子在生物膜形成和结构中的作用尚不清楚。在这项研究中，通过测定生物量和抗生素耐药性来测量呼吸道上皮细胞和角质形成细胞上的生物膜形成，并用扫描电子显微镜观察生物膜形态。所有测试的 GAS 分离株在上皮细胞和角质形成细胞上都形成了具有相似但不完全相同的生物量和抗生素耐药性的生物膜。有趣的是，功能性成熟的生物膜在上皮细胞上形成得更快，但在上皮细胞上结构更密集，并且涂有更多的 ECM。ECM 对于生物膜的完整性至关重要，因为蛋白和 DNA 降解酶会诱导细菌从生物膜中释放出来。非生物表面支持生物膜的形成，但这些生物膜结构不那么密集和有组织。尽管观察到一些形态差异，但在对上皮细胞形成生物膜时，M 蛋白、荚膜或链球菌溶血素 O 并没有起到主要作用。NAD-糖基水解酶是形成生物膜的最佳条件，而链球菌溶血素 S 和半胱氨酸蛋白酶 SpeB 则会损害这一过程。最后，没有发现细胞粘附或自动聚集与 GAS 生物膜形成之间存在相关性。综合这些结果，更好地了解了生物膜形成在 GAS 发病机制中的作用，并可能为未来针对 GAS 感染的治疗提供新的靶点。
