Correlations between morphological, molecular biological, and physiological characteristics in clinical and nonclinical isolates of Acanthamoeba spp

Abstract

Eleven Acanthamoeba isolates, obtained from Acanthamoeba keratitis patients, from contact lens cases of non-Acanthamoeba keratitis patients, from asymptomatic individuals, from necrotic tissue, and from tap water and two reference strains were investigated by morphological, molecular biological, and physiological means in order to discriminate clinically relevant and nonrelevant isolates. All clinically relevant isolates showed Acanthamoeba sp. group II morphology. 18S ribosomal DNA sequencing revealed sequence type T4 to be the most prevalent group among the isolates and also the group recruiting most of the pathogenic strains. Interestingly, within T4 the strains of no clinical relevance clustered together. Moreover, physiological properties appeared to be highly consistent with initial pathogenicity and with sequence clustering. Altogether, the results of our study indicate a correlation between the phylogenetic relationship and pathogenicity.

FIG. 1

18S rDNA neighbor-joining tree of the 10 sequence type T4 isolates. The tree was rooted by T3 and T11 using the T3 strains S-7, Hay & Seal, Panola Mt., and Sawyer and the T11 strains RB:F:1, BH-2 and the T11 isolate 4RE as an outgroup. Bootstrap values are based on 1,000 replicates. The numbers at the nodes represent bootstrap values based on 1,000 replicates.