Corneal Ulcer due to Pseudomonas Infection

This picture shows a severe central corneal ulcer due to Pseudomonas aeruginosa infection. The intense whiteness of the lesion was caused by a deposition of precipitates from the fortified ciprofloxacin eye drops used over a period of several weeks. These were alternated with fortified tobramycin eye drops. Cultures were performed prior to initiating therapy, which confirmed susceptibility of the bacterium to these two antibiotics. Many strains show resistance to multiple antibiotics, but most are still susceptible to aminoglycosides and to the fluoroquinolones.¹

Establishing susceptibility and antibiotic sensitivity is especially important with P. aeruginosa, as the bacterium has proven its ability to become increasingly resistant to antibiotics through several different mechanisms. Pseudomonas is able to produce a biofilm consisting of, among other things, gelatinase, elastase, and alkaline protease. It adheres to corneal epithelial cells and invades them. In this way, it can initiate and maintain the infection.²

A complicating variable is the reaction of patients’ own immune systems. An excessive reaction typically involves over-recruitment of polymorphonuclear leukocytes and cytokines. The chemokines are able to phagocytose and kill P. aeruginosa, but this may also lead to permanent scarring.³

This 84-year-old woman was especially at risk because of two factors: a neurotrophic cornea and contact lens wear. She had been successfully wearing a scleral lens on the eye for more than two years. The lens relieved her chronic discomfort and irritation, corrected her vision to 20/30+, and helped protect the ocular surface. Maintaining her independence, she lived alone and was compliant with her care regimen. Nonetheless, contact lens wear has a positive association with Pseudomonas infections.^2,4 After several weeks of intensive treatment, the ulcer was almost completely resolved, with minimal scarring.

References

1. Subedi D, Vijay AK, Willcox M. Overview of mechanisms of antibiotic resistance in Pseudomonas aeruginosa; an ocular perspective. Clin Exp Optom. 2018 Mar;101;162-171.
2. Pinna A, Usai D, Sechi LA, Molicotti P, Zanetti S, Carta A. Detection of virulence factors in Pseudomonas aeruginosa strains isolated from contact lens-associated corneal ulcers. Cornea. 2008 Apr;27:320-326.
3. Willcox MDP. Pseudomonas aeruginosa infection and inflammation during contact lens wear; a review. Optom Vis Sci. 2007 Apr;84;273-278.
4. Hazlett LD. Role of innate and adaptive immunity in the pathogenesis of keratitis. Ocul Immunol Inflamm. 2005 Apr-Jun;13;133-138.