ACANTHAMOEBA GRIFFINI - MOLECULAR CHARACTERIZATION OF A NEW CORNEAL PATHOGEN

Purpose. Acanthamoeba was isolated from the cornea of a soft contact l ense wearer who had keratitis. The protozoan was also isolated from th e contact lens storage case and the domestic water supply used to clea n the case. Using morphologic features, all three isolates were identi fied tentatively as A. griffini, a species not previously associated w ith keratitis. Complete small subunit ribosomal RNA gene (18S rDNA) se quence analysis was used to characterize further the three isolates. M ethods. 18S rDNA was polymerase chain reaction-amplified from whole ce ll DNA derived from amoebal lysates. The genes were cloned and sequenc ed. Complete sequences of approximately 2800 base pairs were obtained from each culture and compared with those stored in a data base of hom ologous Acanthamoeba sequences.Results. The isolates were unequivocall y identified as A. griffini both by comparison of the gene sequence av ailable for the type strain of the species and the presence of a uniqu e group I intron located within the small subunit rDNA. Sequences obta ined for the three isolates were identical, indicating that they were the same strain. Conclusions. The first direct connection between huma n disease and A. griffini is reported from a case of Acanthamoeba kera titis. The type strain of this species was isolated from a marine envi ronment, but the disease-causing strain was isolated from a domestic w ater supply. The DNA sequences obtained confirmed unequivocally the ep idemiologic association between a keratitis-causing strain of Acantham oeba, the contact lens storage case, and the domestic water supply.