Li-Korotky Ha-Sheng, Lo Chia-Yee, Zeng Fan-Rui, Lo David, Banks Juliane M
Division of Pediatric Otolaryngology, Children's Hospital of Pittsburgh, Pittsburgh, PA 15201, USA.
Int J Pediatr Otorhinolaryngol. 2009 Oct;73(10):1417-22. doi: 10.1016/j.ijporl.2009.07.007. Epub 2009 Aug 13.
Streptococcus pneumoniae, a leading cause of otitis media (OM), undergoes spontaneous intra-strain variations in colony morphology. Transparent (T) variants are more efficient in colonizing the nasopharynx while opaque (O) variants exhibit greater virulence during systemic infections. This study was intended to delineate the underlying molecular mechanisms by which the predominant S. pneumoniae variant efficiently infects the middle ear (ME) mucosa.
Human ME epithelial cells were preconditioned for 24h under one of the three gas/pressure conditions designed to simulate those for (1) normal ME (NME), (2) ME with Eustachian tube obstruction (ETO) and (3) ME with tympanostomy tube placement (TT), and then were incubated with ∼ 10(7)CFU/ml of either T or O variants of S. pneumoniae (6A) for 3h. Relative expression levels of genes encoding virulence factors, PsaA (surface adhesion), SpxB (pyruvate oxidase), Ply (pneumolysin), and LytA (autolysin) were assessed separately in epithelium-attached and supernatant bacteria 3h post infection using real-time PCR.
Basal levels of the virulence molecules in inocula were comparable between two variants. However, relative expression levels of the gene transcripts were significantly induced in epithelium-attached T variants 3h after infection. Comparing with NME and TT conditions, ETO environment produced the largest effect on the differential expression of the virulence genes in the infected ME epithelial cells between T (induced) and O (suppressed) phenotypic pneumococci.
T variant is a predominant phenotype responsible for the pathogenesis of pneumococcal OM.
肺炎链球菌是中耳炎（OM）的主要病因，其菌落形态会发生自发的菌株内变异。透明（T）变体在鼻咽部定植方面更有效，而不透明（O）变体在全身感染期间表现出更强的毒力。本研究旨在阐明主要的肺炎链球菌变体有效感染中耳（ME）黏膜的潜在分子机制。
将人ME上皮细胞在三种气体/压力条件之一（旨在模拟（1）正常ME（NME）、（2）伴有咽鼓管阻塞（ETO）的ME和（3）伴有鼓膜置管（TT）的ME的条件）下预处理24小时，然后与约10(7)CFU/ml的肺炎链球菌（6A）的T或O变体孵育3小时。使用实时PCR分别评估感染后3小时在上皮附着菌和上清液菌中编码毒力因子PsaA（表面黏附素）、SpxB（丙酮酸氧化酶）、Ply（肺炎溶血素）和LytA（自溶素）的基因的相对表达水平。
两种变体接种物中毒力分子的基础水平相当。然而，感染后3小时上皮附着的T变体中基因转录本的相对表达水平显著上调。与NME和TT条件相比，ETO环境对感染的ME上皮细胞中毒力基因在T（诱导）和O（抑制）表型肺炎球菌之间的差异表达产生的影响最大。
T变体是导致肺炎球菌性中耳炎发病的主要表型。
