Study underscores efficacy of simple measures in endophthalmitis prophylaxis

This study evaluated the in vitro susceptibility of postoperative endophthalmitis bacterial isolates to a variety of concentrations and exposure times of povidone-iodine. The results, reported in the January issue of the Journal of Cataract & Refractive Surgery, indicate that exposure to 5% povidone-iodine for 15 minutes or 10% povidone-iodine for five minutes can prevent the growth of most post-cataract surgery endophthalmitis bacterial isolates. While this is an experimental study, it highlights how relatively simple measures may be effective at preventing endophthalmitis.

Organisms were isolated in 30 (68 percent) of the 44 patients diagnosed with postoperative endophthalmitis. Coagulase-negative Staphylococcus was identified in 14 cases (47 percent), Streptococcus species in eight cases (27 percent), Staphylococcus aureus in five cases (17 percent), Bacillus cereus in two cases (6 percent) and Pseudomonas aeruginosa in one case (3 percent).

The authors found that higher povidone-iodine concentrations and longer exposure times were more effective than lower povidone-iodine concentrations or shorter exposure at preventing growth of bacterial isolates. The most effective regimens were 5% povidone-iodine for 15 minutes and 10% povidone-iodine for at least five minutes.

Sixty percent of bacterial isolates remained viable after exposure to 1% povidone-iodine even with an exposure time of 15 minutes, as did 13 percent of bacterial isolates after exposure to 10% povidone-iodine. The authors noted that 10% povidone-iodine applied for one minute was very effective at eradicating all isolates studied except S epidermidis, which required at least five minutes of exposure to this solution for acceptable sterility.

The authors conclude that periocular preparation with povidone-iodine alone may not eradicate all types of postoperative endophthalmitis isolates, and a higher concentration of povidone-iodine and multiple applications may be required in vivo to combat an equal load of in vitro isolates.