Callegan Michelle C, Parkunan Salai Madhumathi, Randall C Blake, Coburn Phillip S, Miller Frederick C, LaGrow Austin L, Astley Roger A, Land Craig, Oh So-Young, Schneewind Olaf
Department of Ophthalmology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd., Oklahoma City, OK 73104, USA; Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd., Oklahoma City, OK 73104, USA.
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 950 Stanton L. Young Blvd., Oklahoma City, OK 73104, USA.
Exp Eye Res. 2017 Jun;159:69-76. doi: 10.1016/j.exer.2017.03.007. Epub 2017 Mar 20.
Bacterial endophthalmitis is a potentially blinding intraocular infection. The bacterium Bacillus cereus causes a devastating form of this disease which progresses rapidly, resulting in significant inflammation and loss of vision within a few days. The outer surface of B. cereus incites the intraocular inflammatory response, likely through interactions with innate immune receptors such as TLRs. This study analyzed the role of B. cereus pili, adhesion appendages located on the bacterial surface, in experimental endophthalmitis. To test the hypothesis that the presence of pili contributed to intraocular inflammation and virulence, we analyzed the progress of experimental endophthalmitis in mouse eyes infected with wild type B. cereus (ATCC 14579) or its isogenic pilus-deficient mutant (ΔbcpA-srtD-bcpB or ΔPil). One hundred CFU were injected into the mid-vitreous of one eye of each mouse. Infections were analyzed by quantifying intraocular bacilli and retinal function loss, and by histology from 0 to 12 h postinfection. In vitro growth and hemolytic phenotypes of the infecting strains were also compared. There was no difference in hemolytic activity (1:8 titer), motility, or in vitro growth (p > 0.05, every 2 h, 0-18 h) between wild type B. cereus and the ΔPil mutant. However, infected eyes contained greater numbers of wild type B. cereus than ΔPil during the infection course (p ≤ 0.05, 3-12 h). Eyes infected with wild type B. cereus experienced greater losses in retinal function than eyes infected with the ΔPil mutant, but the differences were not always significant. Eyes infected with ΔPil or wild type B. cereus achieved similar degrees of severe inflammation. The results indicated that the intraocular growth of pilus-deficient B. cereus may have been better controlled, leading to a trend of greater retinal function in eyes infected with the pilus-deficient strain. Although this difference was not enough to significantly alter the severity of the inflammatory response, these results suggest a potential role for pili in protecting B. cereus from clearance during the early stages of endophthalmitis, which is a newly described virulence mechanism for this organism and this infection.
细菌性眼内炎是一种可能导致失明的眼内感染。蜡样芽孢杆菌可引发这种疾病的一种毁灭性形式，病情进展迅速，在数天内就会导致严重炎症和视力丧失。蜡样芽孢杆菌的外表面可能通过与Toll样受体（TLRs）等天然免疫受体相互作用，引发眼内炎症反应。本研究分析了蜡样芽孢杆菌菌毛（位于细菌表面的粘附附属物）在实验性眼内炎中的作用。为了验证菌毛的存在会导致眼内炎症和毒力增加这一假设，我们分析了用野生型蜡样芽孢杆菌（ATCC 14579）或其同基因菌毛缺陷突变体（ΔbcpA - srtD - bcpB或ΔPil）感染的小鼠眼内实验性眼内炎的进展情况。将100个菌落形成单位（CFU）注射到每只小鼠一只眼睛的玻璃体中部。通过定量眼内杆菌数量和视网膜功能丧失情况，并在感染后0至12小时进行组织学分析来评估感染情况。还比较了感染菌株的体外生长和溶血表型。野生型蜡样芽孢杆菌和ΔPil突变体在溶血活性（1:8滴度）、运动性或体外生长方面（在0至18小时内，每2小时进行一次检测，p>0.05）没有差异。然而，在感染过程中，感染野生型蜡样芽孢杆菌的眼睛中的细菌数量比感染ΔPil突变体的眼睛中的细菌数量更多（在3至12小时，p≤0.05）。感染野生型蜡样芽孢杆菌的眼睛比感染ΔPil突变体的眼睛视网膜功能损失更大，但差异并不总是显著。感染ΔPil或野生型蜡样芽孢杆菌的眼睛出现了相似程度的严重炎症。结果表明，菌毛缺陷型蜡样芽孢杆菌在眼内的生长可能得到了更好的控制，导致感染菌毛缺陷菌株的眼睛中视网膜功能有更好的趋势。虽然这种差异不足以显著改变炎症反应的严重程度，但这些结果表明菌毛在眼内炎早期保护蜡样芽孢杆菌不被清除方面可能发挥了作用，这是针对这种微生物和这种感染新描述的一种毒力机制。
