Tzu G. Wu

Activity of Voriconazole Against Corneal Isolates of scedosporium apiospermum

Purpose. To determine the in vitro antifungal activity of voriconazole, a new triazole, compared with other polyene and imidazole antifungal agents against corneal isolates of Scedosporium apiospermum. Methods. Macro-broth dilution susceptibility testing was performed on five isolates of S. apiospermum obtained from patients with keratomycosis to determine the minimal inhibitory concentrations (MICs) for amphotericin B, natamycin, ketoconazole, itraconazole, and voriconazole. The use of oral voriconazole in the management of a patient with posttraumatic S. apiospermum keratitis is described. Results. S. apiospermum is generally resistant to commonly used topical ophthalmic antifungal agents. The MIC of voriconazole was 0.5 &mgr;g/mL, a concentration lower than that of other imidazoles. Conclusion. Voriconazole has promising activity against S. apiospermum and may prove useful in the management of fungal keratitis.

Immunosuppression Affects the Severity of Experimental Fusarium solani Keratitis

We have established a mouse model of corneal fusariosis that permits the evaluation of fungal infection and pathogenesis. Corneas of immunocompetent and cyclophosphamide-treated adult BALB/c mice were topically inoculated with Fusarium solani after corneal scarification. Eyes were scored for corneal involvement daily for 8 days and at 2 weeks after infection. Eyes were enucleated at various time points for quantitative fungal recovery and histopathological examination. An inoculum-dose response was observed in cyclophosphamide-treated mice, and fungi were recovered from the infected eyes by quantitative microbial culturing. Treatment with cyclophosphamide increased disease severity and delayed fungal clearance. Fungal hyphae, inflammatory cells, and stromal edema were histologically evident within corneal tissue and correlated with disease severity. Although the mouse cornea resists fungal infections, F. solani keratitis could be induced in immunosuppressed mice after surface scarification, which resulted in infection and clinical disease that could be evaluated both in vivo and in vitro.

Molecular analysis of the pediatric ocular surface for fungi.

Purpose. To analyze the conjunctival flora of individuals 21 years of age or less for fungi using polymerase chain reaction (PCR) methodology. Methods. Before povidone-iodine antisepsis, eye-swab specimens were collected from adolescent corneal donors preceding corneal excision and from children during preparation for strabismus surgery. Nucleic acid was extracted from the specimens and analyzed by PCR using primers designed for the detection of broad-spectrum fungal DNA and of Candida albicans -specific DNA. Results. Twelve (38%) of 32 eye donor surfaces and 7 (23%) of 30 patient samples were positive for fungal DNA (P = 0.1). C. albicans DNA was detected in 6 (19%) of the decedents’ eyes but from none of the surgical patients (P = 0.04). Conclusions. Fungi were present on the normal ocular surface of children and adolescents. C. albicans was more likely to be found postmortem than pre-surgically.

Expression of matrix metalloproteinases 2 and 9 in experimental corneal injury and fungal keratitis.

Purpose: Levels of matrix metalloproteinases (MMPs) can be modulated during corneal infection, but little is known about MMP profiles during fungal keratitis. The purpose of this study was to determine the effect of corneal trauma and immunosuppressive treatment on the expression kinetics of MMP-2 and MMP-9 during experimental keratomycosis. Methods: Corneas of immunocompetent and cyclophosphamide-treated adult BALB/c mice were topically inoculated with 1 × 105 culturable units of Fusarium solani or mock-inoculated with or without superficial corneal scarification. Eyes were scored daily for disease severity and processed for zymography after 1.5 hours, 6 hours, 1 day, 4 days, or 8 days. Gelatinase activity was densitometrically quantitated and normalized to MMP-2 and MMP-9 controls. Results: MMP-9 levels in nontraumatized eyes transiently increased at 6 hours after fungal exposure, but this increase was inhibited by cyclophosphamide treatment. Corneal injury significantly induced early MMP-9 expression that returned to baseline levels within 4 days. Cyclophosphamide pretreatment reduced and delayed MMP-9 after scarification. Fusarium exposure dampened the MMP-9 response to corneal trauma in immunocompetent and cyclophosphamide-treated animals. Ocular levels of MMP-2 were not affected by scarification, fungal exposure, or immunosuppressive treatment. Conclusions: Ocular MMP-9 levels, but not MMP-2 levels, increased soon after corneal injury. A similar, although muted, MMP-9 response occurs during early filamentous fungal keratitis, with a kinetic profile similar to corneal disease progression. The early stage of ulcerative keratitis may involve selective regulation of corneal matrix metalloproteinases, suggesting an initial opportunity for therapeutic intervention.