AMEBIC KERATITIS IN A WEARER OF DISPOSABLE CONTACT-LENSES DUE TO A MIXED VAHLKAMPFIA AND HARTMANNELLA INFECTION

Purpose: To support the hypothesis that Acanthamoeba is not a unique c ause of amebic keratitis, we report a case of amebic keratitis in whic h viable Acanthamoeba could not be isolated from corneal tissue. Vahlk ampfia and Hartmannella, two other genera of free-living ameba, were i solated, however, using prolonged culture. Methods: A 24-year-old wear er of soft contact lenses had keratitis. Extensive histologic and micr obiologic investigations were performed on corneal scrape, biopsy, and keratoplasty tissue. Contact lenses, storage case, and the home water supply, where contact lens hygiene was practiced, were examined for t he presence of micro-organisms. Results: No viruses, pathogenic bacter ia, or fungi were detected from corneal tissue samples. Amebae were ob served using light and electron microscopy, but these could not be une quivocally classified using immunocytochemical staining. Viable Vahlka mpfia and Hartmannella, but no Acanthamoeba, were isolated from the co rneal biopsy sample. Indirect immunofluorescence with a range of polyc lonal rabbit antisera raised against axenically cultivated stains of t he three amebal genera was unhelpful because of crossreactivity. A div erse range of micro-organisms was present within the storage case, inc luding the three amebal species. Amebic cysts also were associated wit h the contact lens. Conclusion: A mixed non-Acanthamoeba amebic kerati tis has been identified in a wearer of soft contact lenses where lack of storage case hygiene provided the opportunity for the free-living p rotozoa Vahlkampfia and Hartmannella to be introduced to the ocular su rface. When Acanthamoeba-like keratitis occurs, but where Acanthamoeba cannot be isolated using conventional laboratory culture methods, alt ernate means should be used to identify other amebae that may be prese nt. Polyclonal immunofluorescent antibody staining was unreliable for generic identification of pathogenic free-living amebae in corneal tis sue.