Dougherty J M, McCulley J P, Silvany R E, Meyer D R
Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas.
Invest Ophthalmol Vis Sci. 1991 Oct;32(11):2970-5.
Tetracycline administered in low doses can be effective in the long-term management of patients with meibomian keratoconjunctivitis (MKC). However, the mechanism of action does not appear to be a reduction of bacteria. Seventy-five percent of the ocular staphylococci in such patients are resistant to tetracycline. An alternative mechanism of action could be the inhibition of production of extracellular enzymes by the ocular flora. Inhibition of lipase production could result in lowered levels of toxic hydrolysis products (free fatty acids), which may exacerbate the disease process. The authors tested this hypothesis by examining the differential effect of tetracycline on growth and lipase production in a tetracycline-resistant and tetracycline-sensitive strain of Staphylococcus epidermidis and S. aureus isolated from patients with MKC and Staphylococcal blepharitis. Tetracycline caused significant decreases in the production of lipase in the sensitive and resistant strains of S. epidermidis without concominant decreases in growth. In contrast, S. aureus strains showed parallel decreases in both lipase production and inhibition of growth. The authors propose that the sensitivity of lipase production to tetracycline, in tetracycline-resistant S. epidermidis, may partially explain the clinical improvement observed in MKC patients.
低剂量使用四环素对睑板腺角膜结膜炎（MKC）患者的长期治疗可能有效。然而，其作用机制似乎并非减少细菌数量。此类患者中75%的眼部葡萄球菌对四环素耐药。另一种作用机制可能是抑制眼部菌群产生细胞外酶。抑制脂肪酶的产生可能会降低有毒水解产物（游离脂肪酸）的水平，而这些产物可能会加剧疾病进程。作者通过检测四环素对从MKC患者和葡萄球菌性睑缘炎患者分离出的耐四环素和对四环素敏感的表皮葡萄球菌及金黄色葡萄球菌菌株生长和脂肪酶产生的不同影响，对这一假设进行了验证。四环素可使敏感和耐药的表皮葡萄球菌菌株的脂肪酶产生显著减少，而生长并未随之减少。相比之下，金黄色葡萄球菌菌株的脂肪酶产生和生长抑制则呈现平行下降。作者提出，在耐四环素的表皮葡萄球菌中，脂肪酶产生对四环素的敏感性可能部分解释了在MKC患者中观察到的临床改善情况。
