Clinical and microbiological characteristics of Moraxella keratitis.

Background/aims: To describe the risk factors, clinical features, bacterial subspecies characteristics and treatment outcomes of Moraxella keratitis in a single centre.

Methods: A retrospective review of all patients diagnosed with Moraxella keratitis between November 2012 and December 2017 at the Royal Victoria Eye and Ear Hospital, Dublin, Ireland was performed. Matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry was used to identify subspecies.

Results: Forty-one cases of Moraxella keratitis were identified. Previous ocular surgery and diabetes were the most common local and systemic risk factors. The most common appearance on presentation was an oval-shaped paracentral infiltrate with a mean diameter of 4.2 mm. Mean presenting and final logarithm of minimal angle of resolution visual acuity were 1.307±0.74 and 0.99±1.01, respectively. Surgical procedures, including penetrating keratoplasty, corneal glueing or evisceration, were required to manage nine (22%) patients. Mean time to complete corneal epithelialisation was 32 (range, 7-109) days and mean duration of topical antibiotic therapy was 54 (range, 9-124) days. MALDI-TOF analysis revealed the following subspecies: (16; 39%), (15; 36%), (4; 10%) and (2; 5%). In four cases (10%), subspecies analysis was inconclusive. and . were associated with larger infiltrates on presentation (p<0.05), required more surgical intervention and longer treatment duration (p<0.001).

Conclusion: In this large series of patients from Ireland, Moraxella keratitis was notable for its severity on presentation, slow response to antimicrobial therapy, high risk of surgical intervention and poor visual outcome. We have demonstrated the value of subspecies identification using MALDI-TOF by reporting significant differences in the clinical features and prognosis of and compared with other subspecies.