The evaluation of therapeutic responses in experimental keratomycosis

Keratomycosis in captive red pandas (Ailurus fulgens): 2 cases

Two cases of keratomycosis in captive red pandas (Ailurus fulgens) were diagnosed and treated at a zoo in Melbourne, Australia across a 9-year period. Both cases presented with severe unilateral ocular pain and stromal abscessation of the cornea. A superficial keratectomy was performed in both cases and the diagnosis was confirmed with either cytology or histopathology. Following surgery, a combination of oral, topical and subconjunctival medical therapy contributed to a successful outcome.

The contribution of animal models of aspergillosis to understanding pathogenesis, therapy and virulence

Animal models of aspergillosis have been used extensively to study various aspects of pathogenesis, innate and acquired host-response, disease transmission and therapy. Several different animal models of aspergillosis have been developed. Because aspergillosis is an important pulmonary disease in birds, avian models have been used successfully to study preventative vaccines. Studies done to emulate human disease have relied on models using common laboratory animal species. Guinea pig models have primarily been used in therapy studies of invasive pulmonary aspergillosis (IPA). Rabbits have been used to study IPA and systemic disease, as well as fungal keratitis. Rodent, particularly mouse, models of aspergillosis predominate as the choice for most investigators. The availability of genetically defined strains of mice, immunological reagents, cost and ease of handling are factors. Both normal and immunosuppressed animals are used routinely. These models have been used to determine efficacy of experimental therapeutics, comparative virulence of different isolates of Aspergillus, genes involved in virulence, and susceptibility to infection with Aspergillus. Mice with genetic immunological deficiency and cytokine gene-specific knockout mice facilitate studies of the roles cells, and cytokines and chemokines, play in host-resistance to Aspergillus. Overall, these models have been critical to the advancement of therapy, and our current understanding of pathogenesis and host-resistance.

Comparison of efficacy of topical and oral fluconazole treatment in experimental Aspergillus keratitis

PURPOSE

To investigate the therapeutic role of topical and oral fluconazole treatment using a rabbit model of Aspergillus fumigatus keratitis.

METHODS

Aspergillus fumigatus spores were injected into the corneal stroma of the right eye of 20 rabbits. Forty-eight hours later the rabbits were randomly divided into three groups. Group 1 rabbits (six) were treated with topical fluconazole (2 mg/ml, eight times daily), group 2 rabbits (seven) received oral fluconazole (37.5 mg/kg bid), and group 3 rabbits (seven) were untreated controls. The eyes were examined and photographed with a slit-lamp 2, 6, 10, 16, and 20 days after inoculation and an observer graded the corneas in a masked fashion. Corneal cultures were taken on days 2, 14, and 20 for fungus growth.

RESULTS

At the beginning of treatment, the slit-lamp scores did not differ among three groups. However, on days 6, 10, 16, and 20 the treated groups had statistically significant lower scores compared to the untreated controls. No significant difference was observed between topical and oral treated groups at any examination point. All cultures were positive on day 2, but on days 16 and 20, there were significantly lower positive fungal cultures in both treatment groups compared to the control (p < 0.01, chi square test).

CONCLUSION

Our study showed that both topical and oral fluconazole were effective in lessening the severity of fungal keratitis in a rabbit model and should be considered effective treatment alternatives in the therapy of Aspergillus fumigatus keratitis.

Advances in the management of keratomycosis and Acanthamoeba keratitis

PURPOSE

In the late 1960s, the management of fungal keratitis was a serious unresolved problem. Little was known of the epidemiology of the disease, and there were no antifungal agents formulated for use in the eye.

METHODS

A thorough review of the literature was done back to 1969 on clinical reports and experimental studies for keratomycosis and Acanthamoeba keratitis.

RESULTS

Since 1969, through basic and clinical research, the epidemiology of the disease worldwide is better understood. One new topical antifungal agent, natamycin, with efficacy against filamentous fungi has been developed and the pharmacokinetics of topically applied antifungal drops have been explored. Progress has been slow but the prognosis for keratomycosis has immeasurably improved over the period. Acanthamoeba was first recognized as an ocular pathogen in 1973 and was the cause of an epidemic in the 1980s caused by contaminated contact lens, although other risk factors were also identified. At the onset of the epidemic, there was no known treatment. but as a result of intense research efforts, within a few years a well-defined therapeutic approach had been developed that had a significant impact on the prognosis for this initially devastating infection. For both infections, the role of corticosteroids for controlling the inflammation remains controversial, but the place for keratoplasty is now well defined.

CONCLUSIONS

Although there has been steady progress in the management of both infections, continued research is the way to define more effective medical and surgical therapy.

Oral fluconazole therapy for keratomycosis

A 12-year-old girl with fungal keratitis following injury with a vegetable foreign body was successfully treated with oral fluconazole, a new antifungal agent. The infection resolved completely with good visual recovery. Fluconazole was well tolerated systemically.