Proteus mirabilis may be an uncommon cause of microbial keratitis, but individuals with poor ocular surfaces and contact lens wearers are at increased risk for developing it, a study in Cornea reports. The research team from the University of Pittsburgh Medical Center and the University of Michigan found that when cases of P. mirabilis do arise, treatment with fortified antibiotics or fluoroquinolones seem to provide effective coverage.

In this retrospective study, 26 culture-proven cases of P. mirabilis infections were diagnosed and treated between 1998 and 2019 at the University of Pittsburgh Medical Center. The investigation included 16 eyes of 14 keratitis patients, and the study considered demographic information, ocular risk factors and treatment outcomes.

Patients were approximately 48 years old and underwent follow-up at around six months.

The most common ocular risk factors were poor ocular surface (57.1%) and contact lens use (42.9%). Additionally, 11 patients (78.6%) had positive corneal cultures and 13 (92.9%) had positive conjunctiva or eyelid cultures. The researchers reported all isolates were susceptible to ciprofloxacin, ofloxacin, moxifloxacin, gatifloxacin and cefazolin, and surgical intervention was required in four patients (28.6%).

Average logMAR visual acuity was 1.3 ± 1.0 at presentation and 0.9 6 ± 1.0 at the most recent follow-up visit.

Mo S, Durrani A, Safiullah Z, et al. Proteus mirabilis keratitis risk factors, clinical features, treatment eutcomes, and microbiological characteristics. Cornea. August 24, 2020. [Epub ahead of print]