Time-Kill Assay Results for a Linalool-Hinokitiol-Based Eyelid Cleanser for Lid Hygiene

Purpose: Time-kill testing was performed for a linalool-hinokitiol-based eyelid cleanser against Pseudomonas aeruginosa, Moraxella catarrhalis, Escherichia coli, Serratia marcescens, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, and Pityrosporum ovale to evaluate its efficacy. Methods: An inoculum of 1 mL of each test organism culture was added to 49 mL of test cleanser. At 30 seconds and 1 minute, 1 mL of sample was removed from each test mixture and added to 9 mL of neutralizer. Five milliliters of aliquots were incubated for 48 hours and counted for colony-forming units. Ten percent povidone-iodine was used as a control. Results: At 30 seconds, the linalool-hinokitiol-based eyelid cleanser produced a 99.9999% reduction in P. aeruginosa, a 99.999% reduction in E. coli, a 99.99% reduction in M. catarrhalis and S. marcescens, a 99.9% reduction in MRSA, a 99.2% reduction in S. epidermidis, and a 97.5% reduction in S. aureus. At 1 minute, this cleanser achieved a 95.8% reduction in P. ovale. At 30 seconds, povidone-iodine produced a 99.9999% reduction in P. aeruginosa and M. catarrhalis, a 99.999% reduction in S. marcescens and a 94.9% reduction in S. epidermidis. At 1 minute, 10% povidone-iodine produced a 93.8% reduction in E coli but failed to produce a 1-log reduction in S. aureus or MRSA. Conclusions: This linalool-hinokitiol-based eyelid cleanser may be helpful in the outpatient setting for patients with presurgical, blepharitis, punctal plug and dry eye, and in the inpatient setting for patients who are allergic to iodine, or as an adjunct to povidone-iodine.