Growth and survival of Fusarium solani-F. oxysporum complex on stressed multipurpose contact lens care solution films on plastic surfaces in situ and in vitro.

PURPOSE: To analyze factors implicating the association of ReNu with MoistureLoc (ReNu ML) multipurpose contact lens solution (MPS) with the increased incidence of Fusarium keratitis.
METHODS: Used contact lens cases with and without contact lenses and MPS containers were collected from patients with confirmed or possible Fusarium keratitis. Direct microscopy including transparent adhesive tape preparations and swab cultures were used to determine fungal colonization. Survival and growth of selected isolates of Fusarium spp. in drying MPS on plastic surfaces were determined by microscopy and recoverable colony counts on enriched agar.
RESULTS: Discrete regions of fungal colonization, including occasional microcycle conidiation and chlamydospore formation, were observed on the surfaces of contact lens cases and, less often, on solution containers that had been used by patients with Fusarium keratitis associated with the use of ReNu ML. Isolates provisionally grouped with the F. solani-F. oxysporum complex were inhibited by fresh MPS in original solution containers and contact lens cases, but survived in stressed (drying) films of MPS, particularly ReNu ML. These in vitro test results were similar to the direct in situ observations of the materials from patients.
CONCLUSIONS: Selective, rapid growth and survival of cells of the F. solani-F. oxysporum complex on plastic surfaces, particularly of contact lens cases with stressed ReNu ML films, may explain, in part, the recent Fusarium keratitis outbreak.