FIRST PRIZE - COS Awards of Excellence in Ophthalmic Research - Paper

Authors:Tina Felfeli¹, Samantha B. Kasloff², Jay Krishnan², Sherif R. El-Defrawy³, Rajeev H. Muni³, Tony Mazzulli⁴, Todd A. Cutts². ¹Department of Ophthalmology and Vision Sciences and Dalla Lana School of Public Health, University of Toronto, ²Canadian Science Centre for Human and Animal Health and J.C. Wilt Infectious Diseases Research Centre, Public Health Agency of Canada, ³Department of Ophthalmology and Vision Sciences, University of Toronto, ⁴Department of Laboratory Medicine and Pathobiology, University of Toronto.

Author Disclosure Block:T. Felfeli: None. S.B. Kasloff: None. J. Krishnan: None. S.R. El-Defrawy: None. R.H. Muni: None. T. Mazzulli: None. T.A. Cutts: None.

Abstract Body:

Purpose: Shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in ocular secretions of patients with COVID-19 has been reported, which could serve as a source of infection for ophthalmic staff members. The aim of this study was to determine the virucidal efficacy and contact times for commonly used ophthalmic concentrations of povidone-iodine (PVI) and chlorhexidine gluconate (CHX) against SARS-CoV-2 to help inform the use of pre-procedure topical antiseptic application for ophthalmologists.
Study Design: Basic medical research.
Methods: Vero E6 cells (American Type Culture Collection) were maintained in cell culture medium and used as indicator cell lines for viable virus. All experiments were conducted using low passage SARS-CoV-2 virus stocks. PVI (5% w/v) and CHX (0.05% w/v) were tested at full strength, 1:4 and 1:16 dilutions in phosphate buffered saline for the efficacy testing. Fifty microliters of the antiseptics were added to 10 ul of SARS-CoV-2 and incubated at room temperature for 1, 5, 10, and 30-minute contact times. A total of three experiments were conducted for PVI and CHX for the four time points with each dilution series consisting of three biological replicates per time point. Viable residual SARS-CoV-2 was determined by the Reed-Muench TCID₅₀ procedure in Vero E6 cells. Cytotoxicity of residual chemical antiseptics was pre-determined in all test concentrations of PVI and CHX on Vero E6 cells to delineate assay limits of detection.
Results: No SARS-CoV-2 was detected with PVI at full strength and 1:4 dilution after 1, 5 and 10-minute contact times. The 1:16 PVI dilution substantially decreased viral titers from 4.45 (SD 0.44) to 0.12 (SD 0.24) log₁₀ TCID₅₀/mL after 1 minute of contact time. No virus was recovered from the inoculated suspensions after 5 and 10 minutes of contact time with 1:16 PVI dilution. Full strength CHX did not result in SARS-CoV-2 inactivation (4.35, SD 0.77 vs 4.1, SD 0.43 log₁₀ TCID₅₀/mL) even after 30 minutes of contact time.
Conclusions: These findings indicate that PVI at commonly used ophthalmic concentrations has more effective virucidal activity than CHX in inactivating SARS-CoV-2 in inoculated suspensions; with CHX proving to be ineffective at full concentration. This has important implications for ophthalmologists when selecting an ophthalmic solution that reduces transmissibility of SARS-CoV-2 amongst patients and healthcare providers.