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Povidone-iodine preserves conjunctival flora, does not promote bacterial resistance
Use of povidone-iodine 5% alone without antibiotics reduces cost, potential for community health risk.
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Application of povidone-iodine 5% drops before intravitreal injections without topical antibiotics did not appear to promote bacterial resistance or alter ocular conjunctival flora, according to a study.
Intravitreal injections have become one of the most common ophthalmologic procedures for a variety of retinal diseases, including macular degeneration, retinal vein occlusion and diabetic macular edema. Multiple studies have demonstrated that the use of topical antibiotics after these injections increases bacterial resistance, alters conjunctival flora and may even increase infection risk by selecting for more virulent bacteria, resulting in a shift among specialists toward use of povidone-iodine alone, lead study author Jason Hsu, MD, told Ocular Surgery News.
“Additional studies have shown no significant difference in rates of endophthalmitis whether or not you use antibiotics as long as you use povidone-iodine at the time of the injection,” Hsu said. “Our study was designed to look at whether povidone-iodine by itself would have any adverse effects on the conjunctival flora.”
The study was published in the American Journal of Ophthalmology.
Design, methods
In the prospective interventional case series, 13 treatment-naïve patients with exudative age-related macular degeneration or macular edema due to retinal vein occlusion underwent serial monthly anti-VEGF treatment with sterilization of the ocular surface using only povidone-iodine 5% drops. Patients did not receive antibiotic drops before or after injections.
Conjunctival cultures were obtained before each injection. Of 37 culture-positive samples from baseline and monthly follow-up visits, 47 bacterial isolates were identified, with the most common being coagulase-negative Staphylococcus. Resistance patterns and proportion of coagulase-negative Staphylococcus were similar when comparing baseline to follow-up cultures.
“We’re not affecting the conjunctival flora in any negative way,” Hsu said. “We’re not encouraging the growth of more resistant or virulent bacteria that could be more damaging or more likely to cause endophthalmitis.”
Implications
The study findings confirm that povidone-iodine alone does not promote bacterial resistance as seen with topical antibiotics. When combined with other published studies, povidone-iodine appears to be the safest and most effective antiseptic against endophthalmitis, according to Hsu.
“This was something our group wanted to close the chapter on and confirm that povidone-iodine alone was safe,” Hsu said.
Giving antibiotics at the time of injection in conjunction with povidone-iodine adds cost and potentially increases community health risk by strengthening antimicrobial resistance.
“Essentially you are contributing to the development of resistant organisms, not just for the eye, but even the nasopharyngeal flora, which may lead to sinusitis and pneumonia that is harder to treat. So, it can become a very large community problem to use antibiotics unnecessarily,” Hsu said.
Physician preference plays a role in what concentration of povidone-iodine to use, Hsu said. In this study, the researchers chose the standard 5% concentration. Other protocols, such as whether to instill povidone-iodine both before and after the injection and how long to leave the drop in the eye before injection, are also based on physician preference.
“Most people feel that the optimal antiseptic effect occurs a few minutes after the drop is administered. Therefore, it is best not to inject immediately after giving the drop,” Hsu said.
The drawbacks of the study included the short length of follow-up and the small number of study subjects. – by Steve Ahern