Longer duration of levofloxacin may lead to higher minimum inhibitory concentrations

Kenneth A. Beckman, MD, FACS

Endophthalmitis has long been among the most dreaded complications with cataract surgery. While this severe sight-threatening infection is very rare, this continues to be a source of concern for surgeons. In particular, as no consensus for the most appropriate prophylaxis exists, surgeons are constantly modifying their techniques in search of the best course of care.

In January 2017, Nejima and colleagues published an interesting study on this topic in JCRS, entitled “Effect of the administration period of perioperative topical levofloxacin on normal conjunctival bacterial flora.” In this article, the authors conducted a trial looking at two groups at the time of cataract surgery. In one group, the patients were treated with levofloxacin 1.5% ophthalmic solution for 1 week postop, and in the other group, the patients were treated for 1 month postop. Conjunctival cultures were obtained at various times during the course, looking for both bacterial growth and for the minimum inhibitory concentrations (MIC) for levofloxacin against Staphylococcus epidermidis, one of the leading causes of postoperative endophthalmitis.

In both groups, there was a significant decline in the presence of the bacteria during and at the end of the treatment, with a return to baseline levels 3 months after completing the treatment. Also, in both groups, the MIC increased over the course of treatment to its peak at the conclusion of treatment, and gradually decreased over time following completion of treatment. However, at 3 months following treatment, the group receiving treatment for 1 month had an MIC on average that was twice the MIC for the 1 week treatment group.

These results led to their conclusion that administration of levofloxacin 1.5% during the perioperative course influences the MIC of S. epidermidis. This is significant as surgeons plan their postoperative regimen. Is a patient that uses antibiotics for an extended period of time preoperatively at greater risk for harboring resistant strains of bacteria on their surface when they enter the OR for surgery? In addition, will a prolonged course of postoperative antibiotics make a patient more susceptible to infection as more resistant strains develop on the surface while the eye is vulnerable? While we do not know the answer to these questions, it is clear that we need to continue to investigate the role of prophylactic antibiotics around cataract surgery and strive for a regimen that seems to keep the risks to a minimum.