Cornea & Ocular Surface

Antimicrobial Resistant Keratitis Threatens Older Women, Compromised Corneas

Avatar photoStephen J. Bohacik
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Corneal ulcer
Corneal ulcer (green, just below pupil) on the eye of an 67-year-old woman with microbial keratitis. The yellow and green staining is caused by a fluorescein dye, which allows the ulcer to be seen. A corneal ulcer is an infected break in the surface of the eye that fails to heal and becomes inflamed. In this case the ulcer was caused by microbial keratitis, an infection of the cornea (the transparent membrane covering the front of the eye). Treatment depends on the infectious agent present; for example, bacterial ulcers are treated with antibiotics.
Older women with Corynebacterium spp. often experience the least favorable outcomes among patients with microbial keratitis with antimicrobial resistance.

In patients with microbial keratitis with antimicrobial resistance (AMR), clinical outcomes are often more favorable for those with coagulase-negative staphylococci (CoNS) than Staphylococcus aureus (S. aureus) or Corynebacterium spp., according to research published in Cornea. Study findings also reveal an association between women older than 60 years, previous corneal grafts, previous topical steroid use, larger ulcers, and poor baseline visual acuity and the latter 2 types of microbial keratitis with AMR. 

Researchers conducted a retrospective analysis of 140 patients with microbial keratitis with AMR (CoNS=109, S. aureus=19, Corynebacterium spp.=12) presenting to a single center between 2012 and 2016. They assessed patient records to determine predisposing factors, clinical features, and visual outcomes. 

The investigators observed an association between AMR and women older than 60 years with Corynebacterium spp. (67%, P <.001). They also noted associations with previous corneal graft and topical steroid use (14%, 38%, 58%; P <.001 and 20%, 46%, 50%; P =.05 for the CoNS, S. aureus, and Corynebacterium spp. groups, respectively).

Baseline analysis revealed that 45%, 75%, and 78% (P =.011) of CoNS, S. aureus, and Corynebacterium spp. patients were considered to be blind (visual acuity worse than 3/60) at presentation. These percentages decreased to 28% and 67% in the CoNS and S. aureus groups, respectively, upon final visit, while increasing to 80% in the Corynebacterium spp. group (P =.004). 

“In our study, any case with AMR was statistically more associated with a poor outcome, especially from the S. aureus and Corynebacterium spp. groups,” according to the investigators. “The Corynebacterium spp. group had a longer median healing ulcer time, a final VA worse than 3/60 and slow healing or non-healing ulcers needing diverse treatments.”

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Study limitations include its retrospective nature, single center design, and high loss of patients at follow up. 

Reference

Cabrera-Aguas M, Khoo P, Watson SL. Outcomes of microbial keratitis cases resistant to antimicrobials in Sydney, Australia. Cornea. 2022;41(5):572-578. doi:10.1097/ICO.0000000000002803

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