Pathogenesis and outcome of Paecilomyces keratitis.

Purpose: To examine the clinical pathology and management of Paecilomyces lilacinus keratitis.

Design: Observational case series, literature review, and laboratory study.

Methods: Characteristics and outcome of 17 patients with laboratory-confirmed Paecilomyces keratitis treated at 2 referral centers were combined with 25 previously reported cases. Experimental models were developed by topically inoculating a human corneal isolate of P. lilacinus onto murine eyes and onto human donor corneas.

Results: Of 42 reported eyes with Paecilomyces keratitis, 13 (31%) were associated with chronic keratopathy or previous ocular surgery, 11 (26%) followed corneal trauma, and 10 (24%) occurred in soft contact lens wearers. Medical cure occurred in 13 (31%), including 9 of 31 eyes (29%) treated with natamycin or amphotericin B. Penetrating keratoplasty or other surgery was performed in 29 (69%). In vitro testing of P. lilacinus indicated resistance to natamycin and amphotericin B but susceptibility to ketoconazole and voriconazole. Experimental inoculation after superficial scarification established moderately severe corneal paecilomycosis by hyphae and conidia in immunosuppressed mice and in explanted donor corneas.

Conclusions: P. lilacinus is an emerging fungal pathogen that infects corneal tissue by filamentous invasion with occasional intrastromal sporulation. P. lilacinus keratitis does not reliably respond to natamycin or amphotericin B and has often required therapeutic keratoplasty, but topical azole antifungal agents such as voriconazole appear promising.