Loss of the Group A Streptococcus Regulator Srv Decreases Biofilm Formation In Vivo in an Otitis Media Model of Infection
Loss of the Group A Streptococcus Regulator Srv Decreases Biofilm Formation In Vivo in an Otitis Media Model of Infection
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DOI：
10.1128/iai.00255-10
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发表时间：
2010-11-01
影响因子：
3.1
通讯作者：
Reid, Sean D.
中科院分区：
文献类型：
--
作者：
Roberts, Amity L.;Connolly, Kristie L.;Reid, Sean D.
A组链球菌(GAS)是一种常见的咽炎病原体，但GAS在中耳炎中的作用被低估。在这项研究中，我们试图验证这样一种假设，即GAS在中耳定居，并在代表生物膜的局部三维社区建立自己。为了验证这一假设，龙猫的中耳被一种能够在体外形成生物膜的气体菌株(MGAS5005)或一种由于缺乏转录调控因子SRV而导致生物膜形成不足的菌株(MGAS5005 Delta Srv)感染。感染导致MGAS5005和MGAS5005 Delta srv感染动物中耳内形成大的宏观结构。平板计数、扫描电子显微镜、活/死染色和革兰氏染色显示，MGAS5005和MGAS5005 Delta srv在感染样本中的分布存在差异。从中耳积液中分离到大量的MGAS5005 Delta srv的CFU，MGAS5005 Delta srv随机分布于切除的大体结构中。相比之下，MGAS5005在密集排列的微菌落中被发现，这表明中耳切除的物质中有生物膜。在感染早期，渗出液中MGAS5005的CFU水平明显低于MGAS5005 Delta srv。在MGAS5005 Delta srv背景中，染色体编码的链球菌半胱氨酸蛋白酶(SpeB)的等位基因替换恢复了体内生物膜的形成。有趣的是，我们的结果表明，在中耳炎期间，GAS自然形成生物膜，但经球囊接种栗鼠后，生物膜的形成并不是建立感染所必需的。
Group A Streptococcus (GAS) is a common causative agent of pharyngitis, but the role of GAS in otitis media is underappreciated. In this study, we sought to test the hypothesis that GAS colonizes the middle ear and establishes itself in localized, three-dimensional communities representative of biofilms. To test this hypothesis, the middle ears of chinchillas were infected with either a strain of GAS capable of forming biofilms in vitro (MGAS5005) or a strain deficient in biofilm formation due to the lack of the transcriptional regulator Srv (MGAS5005 Delta srv). Infection resulted in the formation of large, macroscopic structures within the middle ears of MGAS5005- and MGAS5005 Delta srv-infected animals. Plate counts, scanning electron microscopy, LIVE/DEAD staining, and Gram staining revealed a difference in the distributions of MGAS5005 versus MGAS5005 Delta srv in the infected samples. High numbers of CFU of MGAS5005 Delta srv were isolated from the middle ear effusion, and MGAS5005 Delta srv was found randomly distributed throughout the excised macroscopic structure. In contrast, MGAS5005 was found in densely packed microcolonies indicative of biofilms within the excised material from the middle ear. CFU levels of MGAS5005 from the effusion were significantly lower than that of MGAS5005 Delta srv early during the course of infection. Allelic replacement of the chromosomally encoded streptococcal cysteine protease (speB) in the MGAS5005 Delta srv background restored biofilm formation in vivo. Interestingly, our results suggest that GAS naturally forms a biofilm during otitis media but that biofilm formation is not required to establish infection following transbullar inoculation of chinchillas.