Persistent culture positivity in fungal keratitis may indicate need for therapeutic PK

Researchers evaluated the usefulness of repeat cultures after starting antifungal medication for predicting outcomes in fungal keratitis.

Study design

This was a prespecified analysis of the randomized Mycotic Antimicrobial Localized Injection (MALIN) trial. The analysis included 70 individuals with fungal keratitis and visual acuity of 20/70 or worse who were randomized to receive intrastromal injection of voriconazole or topical therapy alone. Corneal cultures were performed at presentation, day 3 and day 7 after beginning antifungal medication.

Outcomes

Twenty-five patients were culture positive at day 3 and 20 remained positive on day 7. Cultures that were positive on day 3 and 7 had a hazard ratio of 2.8 and 3.5, respectively, for requiring therapeutic penetrating keratoplasty (TPK). Positive day 3 cultures did not track with perforation, scar size or final visual acuity. In contrast, positive day 7 cultures tended to have 3 logMAR lines worse visual acuity at 3 months and 1.1 mm larger scar size. Aspergillus ulcers were more likely to remain culture positive on day 7 compared with Fusarium ulcers (P<0.001).

Limitations

This study is a secondary analysis of the MALIN randomized trial. Since it was conducted using a South Indian cohort, there may be limits to the generalizability of these results to other patient populations and geographic locations.

Clinical significance

This study confirms the prognostic utility of repeat corneal cultures on day 3 to help predict the need for TPK in patients with moderate to severe filamentous fungal keratitis. Positive cultures on day 7 may also indicate need for surgery as well as predict visual acuity and corneal scar size at 3 months. Given the turnaround time for fungal cultures, repeat cultures on day 3 instead of day 7 can help guide treatment approaches for these challenging cases, facilitate expeditious treatment and improve outcomes.