Dajcs Joseph J, Austin Megan S, Sloop Gregory D, Moreau Judy M, Hume Emma B H, Thompson Hilary W, McAleese Fionnuala M, Foster Timothy J, O'Callaghan Richard J
Department of Microbiology, Immunology, and Parasitology, Louisiana State University (LSU) Health Sciences Center, New Orleans, Louisiana 70112-1393, USA.
Invest Ophthalmol Vis Sci. 2002 Apr;43(4):1109-15.
To determine the pathogenic role of gamma- and alpha-toxin in a rabbit model of Staphylococcus aureus keratitis.
S. aureus strains Newman (expressing gamma-toxin), Newman Delta(hlg) (deficient in gamma-toxin), Newman Delta(hlg)/pCU1 hlg(+) (chromosomal gamma-toxin-deficient mutant rescued by a plasmid encoding gamma-toxin), and Newman Delta(hla) (alpha-toxin-deficient) were intrastromally injected into rabbit corneas. Eyes were scored by slit lamp examination (SLE), and bacterial colony-forming units (CFU) per cornea were determined at 15, 20, and 25 hours after infection. Histologic examination of corneas was performed. Rabbits were immunized against alpha-toxin and subsequently challenged with S. aureus strain Newman. Western blot analyses of culture supernatants were performed to detect alpha-toxin production.
All strains grew equivalently, producing approximately 7 log CFU per cornea at 25 hours after infection. SLE scores at 20 and 25 hours after infection revealed that strains Newman Delta(hlg) and Newman Delta(hla), although virulent, caused significantly less ocular damage and inflammation than their parent or the gamma-toxin genetically rescued strain (P <or= 0.0006). Histologic and SLEs revealed that all strains except Newman Delta(hla) produced corneal erosions. Rabbits immunized actively or passively to alpha-toxin had reduced SLE scores (P <or= 0.0003 and P <or= 0.0033, respectively) and no epithelial erosions when infected with strain Newman. Western blot analysis demonstrated that strains Newman and Newman Delta(hlg), but not Newman Delta(hla), produced alpha-toxin.
These results illustrate that the virulence of strain Newman involves both alpha- and gamma-toxin, with alpha-toxin mediating corneal epithelial erosions. An additional uncharacterized toxin could also be active in damaging the cornea.
确定γ毒素和α毒素在金黄色葡萄球菌角膜炎兔模型中的致病作用。
将金黄色葡萄球菌菌株纽曼（表达γ毒素）、纽曼Δ（hlg）（缺乏γ毒素）、纽曼Δ（hlg）/pCU1 hlg（+）（由编码γ毒素的质粒拯救的染色体γ毒素缺陷突变体）和纽曼Δ（hla）（α毒素缺陷）基质内注射到兔角膜中。通过裂隙灯检查（SLE）对眼睛进行评分，并在感染后15、20和25小时测定每只角膜的细菌菌落形成单位（CFU）。对角膜进行组织学检查。用α毒素对兔进行免疫，随后用金黄色葡萄球菌菌株纽曼进行攻击。对培养上清液进行蛋白质印迹分析以检测α毒素的产生。
所有菌株生长情况相当，在感染后25小时每只角膜产生约7 log CFU。感染后20和25小时的SLE评分显示，菌株纽曼Δ（hlg）和纽曼Δ（hla）虽然具有毒性，但与它们的亲本或γ毒素基因拯救菌株相比，引起的眼部损伤和炎症明显更少（P≤0.0006）。组织学检查和SLE显示，除纽曼Δ（hla）外，所有菌株均导致角膜糜烂。主动或被动免疫α毒素的兔在感染菌株纽曼时SLE评分降低（分别为P≤0.0003和P≤0.0033），且无上皮糜烂。蛋白质印迹分析表明，菌株纽曼和纽曼Δ（hlg）产生α毒素，而纽曼Δ（hla）不产生。
这些结果表明，菌株纽曼的毒力涉及α毒素和γ毒素，其中α毒素介导角膜上皮糜烂。另一种未鉴定的毒素也可能在损伤角膜中起作用。
