In vitro antimicrobial activity of a new ophthalmic solution containing povidone-iodine 0.6% (IODIM®)

Purpose To assess the in vitro antimicrobial activity of a new commercial ophthalmic solution containing povidone-iodine 0.6% (IODIM (R)). Methods Staphylococcus aureus ATCC 43300, Pseudomonas aeruginosa ATCC 27853, three ocular bacterial isolates (1 S. epidermidis, 1 S. aureus, 1 P. aeruginosa) and five Candida species were used. The bacterial and fungal isolates were cultured on Columbia blood agar base plates and Sabouraud-dextrose agar plates, respectively and incubated overnight at 37 degrees C. Bacterial and fungal suspensions in sterile saline solution were prepared to an optical density equal to 0.5 McFarland standard (approximately 10(8) CFU/ml). Suspensions of the isolates were made in IODIM (R) solution to obtain a final concentration of 10(6) CFU/ml. The suspensions were then distributed in conical tubes in a final volume of 1 ml and incubated at 37 degrees C. At different time-points (1, 5, 10, 15, 20, 25, 30 min and 24 hr), 10 mu l of each suspension was removed, seeded on Columbia blood agar base and Sabouraud-dextrose agar plates and then incubated for 24 hr at 37 degrees C. Positive and negative controls were included in all experiments. Results After 5-min incubation, there was no bacterial growth on any plate. Conversely, IODIM (R) failed to kill the Candida isolates after 30 min' exposure and needed 24 hr to eradicate the organisms. Conclusion IODIM (R) ophthalmic solution showed in vitro antimicrobial activity against S. epidermidis, S. aureus, P. aeruginosa and Candida species. Results suggest that it may be a potential candidate for the treatment of ocular surface infections and antimicrobial prophylaxis before intravitreal injections.