The gram-negative bacteria Serratia marcescens is a common cause of keratitis and conjunctivitis, often associated with contact lens wear, topical medication use and an abnormal corneal surface. In a new retrospective observational study, researchers evaluated the risk factors and treatment outcomes of ocular infection due to S. marcescens. Cases were reviewed from 51 patients over an 18-year period for ocular risk factors that included visual acuity (VA), medical management and time to epithelial defect closure.

The most prevalent ocular risk factors were contact lens use (68.6%), corneal disease (52.9%) and history of ocular surgery (41.2%). About half of the patients presented with a central ulcer (49%), large infiltrate and hypopyon (43.1%). Worse outcomes were associated with older age, infiltrate size, presence of hypopyon, worse initial VA, longer time to epithelial defect closure and a history of glaucoma, and many cases also had a history of ocular surgery—including failed grafts.

The study found a significant association between history of glaucoma and worse visual outcomes, and the authors suggest this could be related to the use of antiglaucoma drops—as noted in a previous study.

In addition, 11.8% of the patients used topical steroids at the time, and other previous studies have found a relation with topical steroid use and keratitis development.

“This association is explained by the consequent suppression of immune defense as well as contamination of the topical eyedropper itself,” the authors explained in their study. “Contamination of eyedroppers has previously been associated with microbial keratitis, including S. marcescens, as the collection of moisture surrounding the cap and bottle tip can support growth of Serratia.

The authors concluded the outcomes show ocular infections are generally manageable with antibiotic drops, infrequently adjunctive treatment or surgical intervention. They noted several complications as well.

“Complications observed during the course of infection included antibiotic toxicity, pannus, ruptured globe, failed PKP, superimposed viral infection, corneal perforation, steroid-induced glaucoma secondary to HSV infection, and scleritis secondary to rheumatoid arthritis,” the authors concluded. “Although rare, these findings suggest the potential seriousness of infection and necessity for adequate early treatment in cases of S. marcescens ocular infection.”

Atta S, Perera C, Nayyar S, et al. An 18-year overview of Serratia marcescens ocular infection. Eye & Contact Lens. 2021; 1-5.