Discrimination between Clinically Relevant and Nonrelevant Acanthamoeba Strains Isolated from Contact Lens- Wearing Keratitis Patients in Austria

Abstract

Eighteen cases of Acanthamoeba-associated keratitis among contact lens wearers seen at the Department of Ophthalmology, Karl-Franzens-University, Graz, Austria, between 1996 and 1999 are reviewed. The amoebae were proven to be the causative agents in three patients. The aim of our study was to discriminate between clinically relevant and nonrelevant isolates and to assess the relatedness of the isolates to published strains. Altogether, 20 strains of free-living amoebae, including 15Acanthamoeba strains, 3 Vahlkampfiastrains, and 2 Hartmannella strains, were isolated from clinical specimens. The virulent Acanthamoebastrains were identified as A. polyphaga and two strains ofA. hatchetti. To our knowledge this is the first determination of keratitis-causing Acanthamoebastrains in Austria. Clinically relevant isolates differed markedly from nonrelevant isolates with respect to their physiological properties. 18S ribosomal DNA sequence types were determined for the three physiologically most-divergent strains including one of the keratitis-causing strains. This highly virulent strain exhibited sequence type T6, a sequence type not previously associated with keratitis. Sequence data indicate thatAcanthamoeba strains causing keratitis as well as nonpathogenic strains of Acanthamoeba in Austria are most closely related to published strains from other parts of the world. Moreover, the results of our study support the assumption that pathogenicity in Acanthamoeba is a distinct capability of certain strains and not dependent on appropriate conditions for the establishment of an infection.

Isolation and Genotyping of Acanthamoeba Strains from Soil Sources from Jamaica, West Indies

“…; Walochnik et al. ). Although growth of Acanthamoeba at and over 37 °C is indicative of pathogenic potential, Schuster () proved that some clinical isolates grow better at 30 °C.…”

A rapid and reliable method for the clonal isolation of Acanthamoeba from environmental samples

“…Moreover, Acanthamoeba serves as a carrier for different microorganisms to humans, acting as a vehicle for the circulation of pathogens between the environment and humans (Krusnell and Linder, 2001;Huws et al 2008). Various Acanthamoeba species have been reported to be able to cause keratitis and other human infections, among which the most prevalent are A. castellani, A. polyphaga, A. rhysodes and A. hatchetti (Walochnik et al 2000a;Khan 2006). Although easily recognized at the genus level by their polygonal cysts, the accurate Acanthamoeba species determination and pathogenic potential involves molecular analysis (PCR, RFLP-PCR or DNA sequencing) and several behavioral tests (osmotolerance, temperature tolerance and cytotoxicity assays) which can require axenic and clonal amoeba cultures (Walochnik et al 2000b).…”

Molecular and Physiological Evaluation of Subtropical Environmental Isolates of Acanthamoeba spp., Causal Agent of Acanthamoeba Keratitis

“…One genotype, designated T4, has been found in nearly all AK infections. Rarely, genotypes T3 [Ledee et al 1996) and T11 (Khan et al 2002), and in one case genotype T6 (Walochnik et al 2000a) have been observed in AK infections. Other infections caused by Acanthamoeba spp.…”