Incidence and microbiological profile of mycotic keratitis in a tertiary care eye hospital: A retrospective analysis

Abstract

Purpose: To determine the incidence and microbiological profile of mycotic keratitis seen at a tertiary care eye hospital.

Materials and methods: A retrospective review of microbiology records of patients presenting with suspected microbial keratitis seen between January 2006 and December 2009 was performed. Patients with positive fungal cultures were further analyzed for the type of fungus isolated and associated bacterial pathogens.

Results: Microbiology records of 2300 patients with suspected microbial keratitis were reviewed. A microbiological diagnosis of mycotic keratitis was established in 87 (3.8%) patients over a four year period based on positive fungal cultures. The yearly incidence of mycotic keratitis was 3.2% (2006), 4.9% (2007), 3.3% (2008) and 3.6% (2009). Filamentous fungi were isolated more often than yeasts. Aspergillus species followed by Fusarium species and Trichophyton species were the commonest filamentous fungi isolated while Candida albicans was the most frequently encountered yeast. Mixed infections due to fungal and bacterial pathogens were seen in 25/87 (28.7%) patients.

Conclusion: Cumulative incidence of mycotic keratitis was 3.8% over a four year period. Aspergillus species and Candida albicans were the most frequent pathogenic organisms causing mycotic keratitis in this part of the world. Mixed infections were seen in 28.7% of the patients. Knowledge of the "local" etiology within a region may be valuable in the management of mycotic keratitis in instituting an empirical therapy, especially when facilities for microscopy, cultures and antifungal susceptibility are not readily available. The baseline information presented will also be helpful in the planning of a corneal ulcer management strategy and for future studies on mycotic keratitis.

Keywords: Incidence; Microbiological profile; Mycotic keratitis.

Figure 1

Diffuse illumination of the right eye with Trichophyton shoenleinii keratitis. Note the central thick infiltrate and the hypopyon.

Figure 2

Slit lamp view of the right eye with Trichophyton shoenleinii keratitis after 2 months of therapy. Note the reduced infiltrate and the absence of hypopyon.

Figure 3

Diffuse illumination of the right eye with Candida utilis keratitis: Note the infiltrate along the suture.

Figure 4

Histological appearance of the corneal tissue showing corneal stromal thinning with extensive inflammatory infiltrate, X 40, Hematoxylin & Eosin stain.

Figure 5

The appearance of yeast cells with special stain within the corneal stromal lamellae, X 2000, Gomori’s Methanamine Silver stain.