Time-Kill Comparison of Povidone Iodine to Hypochlorous Acid against Endophthalmitis Isolates of Staphylococci

TLDR: In this article, the antibacterial activity of Povidone Iodine (PI) and Hypochlorous Acid (HA) were compared against endophthalmitis isolates of Staphylococcus aureus and coagulase-negative Staphymus using time-kill studies.

Abstract: Purpose: We compared the antibacterial activity of Povidone Iodine (PI) and Hypochlorous Acid (HA) against endophthalmitis isolates of Staphylococcus aureus and coagulase-negative Staphylococcus using time-kill studies. Methods: Time-kill studies of PI, HA (0.008%), and HA (0.01%, Avenova), were conducted in duplicate against MethicillinSusceptible Staphylococcus aureus (MSSA), Methicillin-Resistant Staphylococcus aureus (MRSA), and Coagulase Negative Staphylococcus (CNS) at time points 1, 2, 10, and 30 minutes. Each antiseptic was inoculated to a final bacterial concentration of 106 CFU/mL. The main outcome measure was based on a bactericidal decrease in colony counts units (CFU) (3 log10 or 99.9% decrease). Results: At 1 minute, HA (0.008% and 0.01%) were more bactericidal than PI for decreasing the CFU of MRSA, MSSA, and CNS (p=0.045, Fisher’s Exact Test). At 2 minutes, the bactericidal effect was equivalent for PI and HA (0.008% and 0.01%) against the three Staphylococcal groups. The bactericidal effects of HA 0.008% and HA 0.01% were equivalent at all time points against all three Staphylococcal groups. Conclusions: Povidone iodine is the current gold standard for endophthalmitis prophylaxis. This in vitro study supports a 2-minute contact time between Staphylococci and PI for a bactericidal effect. The contact time between HA (0.008% and 0.01%) and Staphylococci for a bactericidal effect appears to be reduced to 1 minute.