Acanthamoeba genotype T4 from the UK and Iran and isolation of the T2 genotype from clinical isolates.

The majority of the keratitis-causing Acanthamoeba isolates are genotype T4. In an attempt to determine whether predominance of T4 isolates in Acanthamoeba keratitis is due to greater virulence or greater prevalence of this genotype, Acanthamoeba genotypes were determined for 13 keratitis isolates and 12 environmental isolates from Iran. Among 13 clinical isolates, eight (61.5%) belonged to T4, two (15.3%) belonged to T3 and three (23%) belonged to the T2 genotype. In contrast, the majority of 12 environmental isolates tested in the present study belonged to T2 (7/12, 58.3%), followed by 4/12 T4 isolates (33.3%). In addition, the genotypes of six new Acanthamoeba isolates from UK keratitis cases were determined. Of these, five (83.3%) belonged to T4 and one was T3 (16.6%), supporting the expected high frequency of T4 in Acanthamoeba keratitis. In total, the genotypes of 24 Acanthamoeba keratitis isolates from the UK and Iran were determined. Of these, 17 belonged to T4 (70.8%), three belonged to T2 (12.5%), three belonged to T3 (12.5%) and one belonged to T11 (4.1%), confirming that T4 is the predominant genotype (S2=4.167; P=0.0412) in Acanthamoeba keratitis.