MYCOTIC CORNEAL ULCERS

A presentation of culture-positive corneal donors and the effect on clinical outcomes

PURPOSE

Donor-to-host transmission of infectious agents is a rare but well-recognised complication of corneal transplantation and may carry a grave visual prognosis. In this case series, we describe the clinical features and risk factors of using culture-positive donor corneas for transplantation.

METHODS

Retrospective chart review of a series of patients who underwent either penetrating keratoplasty (PK) or Descemet's stripping automated endothelial keratoplasty (DSAEK) with positive microbiology cultivation during routine assessment of donor corneal tissue obtained at the time of surgery. Donor and recipient characteristics, tissue preparation and surgical parameters, clinical signs and outcomes were registered.

RESULTS

Eleven patients who received culture-positive corneal grafts were identified: six with Candida, three with Gram-positive bacteria and two with Gram-negative bacteria. Three patients developed clinical keratitis after routine DSAEK using corneas contaminated with Candida species. The median death-to-preservation time (DPT) of these three donor corneas was 18.08 (range 18.08 to 20.90) h, while in the remaining eight donors, it was 12.27 (range 9.32 to 20.47) h. Despite the initiation of antifungal treatment, all three cases required explantation of the graft and a subsequent re-DSAEK.

CONCLUSIONS

The use of donor corneas that are culture-positive for Candida carries a risk for developing postoperative keratitis and the risk may be higher in DSAEK. Unlike the cold storage technique employed for donor corneas described in this case series, organ culture technique requires microbiological screening and supplementation of an antifungal agent which may reduce the risk of donor-to-host transmission of fungal infection.

The changing spectrum of fungal keratitis in south Florida

PURPOSE

To review the clinical experience with fungal keratitis in south Florida over a 10-year period.

METHODS

One hundred twenty-five cases of fungal keratitis were identified in the microbiology laboratory records between January 1982 and January 1992. The medical record of each patient was reviewed.

RESULTS

The most commonly associated risk factor was trauma (44%). Fungal keratitis developed in five patients using extended wear contact lenses and one patient wearing a therapeutic bandage contact lens. Clinical features included irregular, feathery margins (62%), a dry, rough texture (47%), and satellite lesions (41%). An initial positive culture was obtained in 90% of patients, with a majority of cultures becoming positive within 48 hours. The Fusarium sp accounted for 62% of the isolates, with Fusarium oxysporum being the most commonly isolated organism. New fungal isolates include Candida parapsilosis, Aspergillus terreus, Candida tropicalis, and Trichosporon beigellii. Natamycin 5% suspension was the initial antifungal agent used for 91% of the patients, with an average duration of treatment of 38 days. Twenty-five patients were treated with oral ketoconazole for a median duration of 2 weeks, in addition to topical antifungal therapy. Thirty-four patients (27%) required a penetrating keratoplasty. Six patients had recurrence of fungal keratitis after penetrating keratoplasty.

CONCLUSIONS

Trauma, including contact lens wear, is the most commonly associated risk factor. The fungal organisms can be readily identified in culture. F. oxysporum is the most common organism, with new isolates identified. The mainstay of therapy is topical natamycin with the increasing use of imidazoles.

Mycotic keratitis--an underestimated mycosis

Mycotic keratitis, an important ophthalmologic problem, especially in outdoor workers in the tropics, is frequently caused by filamentous fungi such as species of Fusarium, Aspergillus and Curvularia, and by yeast-like fungi such as Candida. A rapid, presumptive diagnosis can be made by recognition of certain typical clinical features and by direct microscopic detection of fungi in corneal scrapings stained by various methods. The diagnosis is confirmed by culture. In difficult cases, microbiological studies on corneal biopsies or histopathological studies on tissue sections may need to be performed. The use of fluorescein-conjugated lectins and similar diagnostic tools is aimed at providing rapid, species-specific detection of fungi in corneal tissue. Antifungal therapy must be instituted as soon as the diagnosis is made. While keratitis due to Aspergillus, Candida and dematiaceous fungi can be successfully treated by many of the currently available polyenes and azoles, the treatment of Fusarium keratitis still frequently requires the use of pimaricin or econazole. Treatment by the oral and parenteral routes may prove useful in severe mycotic keratitis. Surgery may need to be performed on cases unresponsive to medical therapy or where serious complications are likely to occur. The pathogenesis of mycotic keratitis appears to involve agent factors, such as invasiveness and toxigenicity, and host factors, such as trauma and intrinsic defects in resistance. Areas for future research include the development of rapid, species-specific diagnostic aids, of broad-spectrum antifungal compounds active by various routes, and of therapeutic modalities which act on the fungus and on molecules involved in the pathogenesis of the condition.

Efficacy of miconazole in experimental keratomycosis

For the first time comparative efficacy of 1% miconazole in ointment base and drops has been evaluated against Candida, Aspergillus and Fusarium organisms in experimental keratomycosis. The findings of the present study reveal that miconazole in ointment drug delivery system has the advantage of being more effective in healing the fungal ulcers and associated lesions. It requires much less frequent application than drops, a parameter of great importance in improving patient compliance. Miconazole ointment was well tolerated by the rabbit eye and produced no ocular or systemic toxicity. The present study confirms that miconazole is a broad-spectrum antifungal agent and it could be a better alternative to presently available drugs to treat human keratomycosis.

Clinical and experimental keratitis due to Curvularia lunata (Wakker) Boedijn var. aeria (Batista, Lima and Vasconcelos) Ellis

A case of mycotic keratitis due to Curvularia lunata var. aeria is reported for the first time from India. Direct microscopic examination of the corneal scrapings in KOH (50 g1(-1)), stained with lactophenol cotton blue, revealed brown septate hyphae and the cultures were found positive for fungus. It was identified as C. lunata (Wakker) Boedijn var. aeria (Batista, Lima and Vasconcelos) Ellis (IMI 253204) and its growth was better at 28 degrees C than at 37 degrees C. In vitro, the fungus was most sensitive to amphotericin B followed by miconazole nitrate, clotrimazole and triphenyltin isoselenocyanate 4-picoline which had the same activity. Lactones were least active and tolciclate and arnebins and inactive. The fungus produced experimental keratomycosis in the rabbit cornea and the infection severity as well as histopathological changes were more pronounced in rabbits that received penicillin, streptomycin and cortisone.

Frequency and significance of fungal isolations from conjunctival sac and their role in ocular infections

Five hundred conjunctival swabs, from 150 males and 100 females with no history of ocular infections, were collected and cultured for the isolations of fungi. Eighty (16%) of the total specimens yielded positive fungal isolations. The isolation rate was more from the males than the females subjects. Mycelial fungi were predominant than the yeast organisms. Aspergillus species were the commonest isolates with A. flavus taking the lead in the isolations being positive 16 of the total 24 Aspergillus species isolated. A variable rate of fungal isolations was observed in different months of the year. The percentage of the isolations increases after the local use of Efcorlin-N. Nineteen of the 20 eyes studied did not yield the same fungal species in the repeated samples.

The incidence of adverse reactions from steroid/antiinfective combinations

Steroid/antiinfective combinations have a number of advantages over the separate ingredients, but the possibility of complications has been a subject of concern. Based on data obtained from the files of eight pharmaceutical companies and the health registry records of the United Kingdom, Australia and New Zealand for the period 1964-1973, it is concluded that the statistical incidence of adverse reactions was no greater with the steroid/antiinfective combinations than with their separate ingredients. In addition, there was no increase in incidence of the reactions during the same period with combinations. These conclusions were borne out by adverse reaction data reported in the literature and in certain unpublished prospective clinical studies. It was not feasible to obtain data from ophthalmologists who may have observed adverse reactions, but not reported them. A critical evaluation by Dr. Philip Ellis follows the review.

Fungal flora of the conjunctival sac in healthy and diseased eyes

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