Moxifloxacin-resistant and moxifloxacin-susceptible Staphylococcus aureus Keratitis: Outcomes from a 10-year...

Fluoroquinolones, specifically moxifloxacin are commonly used to treat bacterial keratitis. However, recent clinical evidence assessing the clinical outcomes in bacterial keratitis cases resistant to moxifloxacin remains sparse. This study evaluates the clinical characteristics and outcomes in cases of Staphylococcus aureus keratitis with in vitro resistance to moxifloxacin.

Retrospective clinical cohort study.

Keratitis patients with cultures positive for Staphylococcus aureus at the University of Pittsburgh Medical Center, were identified between July 2012 and June 2022.

A total of 104 patients with culture-confirmed Staphylococcus aureus keratitis were included in the study. Patients infected by moxifloxacin-resistant bacteria (n = 32) were significantly older (74.32 ± 17.41 years) than moxifloxacin-susceptible infections (55.56 ± 20.86 years, p < 0.0001). Moxifloxacin resistance was identified in 29.8 % of cases, including methicillin-susceptible (4.8 %) and methicillin-resistant Staphylococcus aureus (25.96 %) isolates. The most common risk factors for moxifloxacin resistance were ocular surface disease (35.5 %) and history of prior infection (32.2 %). Moxifloxacin-resistant Staphylococcus aureus was associated with larger epithelial defects (18.18 ± 4.93 mm² vs. 5.10 ± 0.76 mm², p < 0.0001), longer healing times (42.42 ± 6.75 days vs. 32.2 ± 3.56 days, p < 0.0001), and higher rates of corneal perforation (19.3 % vs. 4.2 %; p = 0.0317). Visual acuity outcomes were significantly worse in the resistant group, with minimal improvement from baseline (1.87 ± 0.14 LogMAR) to final follow-up (1.8 ± 0.18 LogMAR), compared to the moxifloxacin-susceptible group (from 1.46 ± 0.11 LogMAR to 1.15 ± 0.11 LogMAR, p < 0.0001). Enucleation was required in 9.6 % of resistant cases.

The current study determined significant differences in clinical characteristics and outcomes among corneal ulcers caused by moxifloxacin-resistant Staphylococcus aureus.