Mullin G S, Rubinfeld R S
Department of Ophthalmology, Washington Hospital Center, Washington, DC, USA.
Cornea. 1997 Nov;16(6):662-5.
Topical anesthetics are commonly used prior to obtaining bacterial cultures in ulcerative keratitis. We performed an in vitro study designed to test both the bacteriostatic and bactericidal effects of commercially available preserved topical anesthetic agents.
Proparacaine, tetracaine, cocaine, and sterile water solutions were applied to filter paper disks, which were then placed on Mueller-Hinton agar plates that had previously been inoculated with known quantities of Pseudomonas aeruginosa and Staphylococcus aureus. After 24 h of incubation, zones of inhibition were measured and recorded.
Proparacaine strongly inhibited the growth of S. aureus at all concentrations (0.5%, 0.25%, 0.125%) and inhibited growth of P. aeruginosa at 0.5% and 0.25% but not at 0.125% concentration. Tetracaine also inhibited S. aureus at 0.5% and inhibited P. aeruginosa at 0.5% and 0.25% concentrations. Cocaine exhibited no inhibition of S. aureus and exhibited mild inhibition of P. aeruginosa growth only at the 4% concentration.
The in vitro antibacterial effect of topical anesthetics suggests one possible reason why bacterial culture yields in clinical ulcerative keratitis are suboptimal. We propose that clinicians consider the use of a 1% or 2% cocaine solution instead of standard commercial topical anesthetics in the management of individual cases of ulcerative keratitis and in future clinical bacterial keratitis studies.
在获取溃疡性角膜炎的细菌培养物之前，通常会使用局部麻醉剂。我们进行了一项体外研究，旨在测试市售的含防腐剂局部麻醉剂的抑菌和杀菌效果。
将丙美卡因、丁卡因、可卡因和无菌水溶液涂在滤纸片上，然后将其放置在先前已接种已知数量铜绿假单胞菌和金黄色葡萄球菌的穆勒-欣顿琼脂平板上。孵育24小时后，测量并记录抑菌圈。
丙美卡因在所有浓度（0.5%、0.25%、0.125%）下均强烈抑制金黄色葡萄球菌的生长，在0.5%和0.25%浓度下抑制铜绿假单胞菌的生长，但在0.125%浓度下无此作用。丁卡因在0.5%浓度下也抑制金黄色葡萄球菌，在0.5%和0.25%浓度下抑制铜绿假单胞菌的生长。可卡因对金黄色葡萄球菌无抑制作用，仅在4%浓度下对铜绿假单胞菌的生长有轻度抑制作用。
局部麻醉剂的体外抗菌作用提示了临床溃疡性角膜炎细菌培养结果不理想的一个可能原因。我们建议临床医生在处理个别溃疡性角膜炎病例以及未来的临床细菌性角膜炎研究中，考虑使用1%或2%的可卡因溶液而非标准的市售局部麻醉剂。
