Relative in vitro Rates of Attachment and Penetration of Hydrogel Soft Contact Lenses by Haplotypes of Fusarium

Abstract

Purpose: : To investigate the relative abilities of different genotype groups of the Fusarium solani (FSSC) - F. oxysporum (FOSC) complexes to attach to and invade hydrogel contact lenses.

Methods: : Silicone hydrogel (SH) and traditional HEMA soft contact lenses were exposed to conidia (10⁴ ml^-1) in phosphate buffered saline (PBS) of representative isolates of different genotypes of fusaria associated with the Fusarium keratitis outbreak of 2004-2006. Select lenses and fungi were reexamined under conditions of organic enrichment. The lenses were incubated with shaking at ambient temperatures and whole lenses examined microscopically and with digital scanning for the presence of penetration pegs (PP).

Results: : Attachment to and penetration of balafilcon A lenses in PBS within 96 h was observed with representative isolates of FSSC group 1-a, 1-b and 2-d. Densities and coiled morphology of the PP were similar. Eight of eight FOSC failed to attach or form PP in PBS without prior sorption of organics by the lens. Generally FSSC group 1 isolates gave the more rapid development of PP, while PP by one representative of FSSC 2-c (ATCC 36031, a standard challenge strain) and 3 of 5 isolates representing FSSC group 2-d required prolonged incubation (>17 days) and/or organic enrichments. Attachment to lotrafilcon lenses was marked by representatives of all genotypes, but depth and numbers of PP were usually less than observed with balafilcon A lenses. The development of PP in etafilcon A and galyfilcon A required extended incubations (>21 days) relative to balafilcon A lenses.

Conclusions: : The data indicate that the degrees of attachment to and penetration of hydrogel soft contact lenses varies with the strain and lens type. Vigorous and rapid lens penetration without organic enrichments trended to be associated more often with FSSC group 1 isolates and sparse to latent with FOSC and FSSC 2-c and group 3.

Keywords: contact lens • fungal disease