Acanthamoeba Genotype T4 Research Articles

Isolation and identification of Acanthamoeba species related to amoebic encephalitis and nonpathogenic free-living amoeba species from the rice field

Isolation and characterization of the clinically relevant amphizoic amoebas in vegetated farmlands, which may present a risk to farmers' health. Acanthamoeba species was isolated and characterized via morphological and molecular means in the rice field where the patient was exposed to rice paddy water which most probably was the point of infection. An Acanthamoeba sp. abundant in the rice field was identified. Genotyping showed the strain to be genotype T4, which was identical to the amoebic parasite found in patient's cerebrospinal fluid. During the course of the study, three nonpathogenic free-living amoeba species were also isolated and characterized for the first time in Taiwan. This study successfully located a possible source of granulomatous amoebic encephalitis in a patient and provided the first evidence that Acanthamoeba genotype T4 may be a potential pathogen in Taiwan. The integration of field survey, clinical data and morphological and genetic examination represents a sound strategy for investigation of the possible role of free-living amoebae in causing human diseases. Future work should include investigating the potential contributory role of other nonpathogenic free-living protozoa in disease of livestock or even human.

Identification of Acanthamoeba genotype T4 and Paravahlkampfia sp. from two clinical samples

In this study, two free-living amoebae strains, Acanthamoeba genotype T4 and Paravahlkampfia sp., which were isolated from keratitis cases are presented. While the Acanthamoeba strain was isolated as a single agent, the Paravahlkampfia strain was found together with herpes simplex virus. Neither of the patients were contact lens wearers, but they did have a history of minor corneal trauma. Amoebae were detected on non-nutrient agar covered with Escherichia coli. Based on PCR-amplified 18S rRNA-gene analysis the first isolate was identified as Acanthamoeba genotype T4 and the second as Paravahlkampfia sp. In thermotolerance tests, the maximum temperature at which trophozoites continued to divide was determined as 37 degrees C for this Acanthamoeba strain and 35 degrees C for the Paravahlkampfia strain. To the best of our knowledge, the Acanthamoeba strain described herein is the second molecularly identified Acanthamoeba strain in an Acanthamoeba keratitis patient in Turkey. However, the Paravahlkampfia isolate is believed to be the first strain that has been isolated from a keratitis patient and has been molecularly differentiated from Vahlkampfia.

Detection of Four Adenovirus Serotypes within Water-Isolated Strains of Acanthamoeba in the Canary Islands, Spain

We surveyed 236 potentially pathogenic Acanthamoeba strains, isolated from water sources in the Canary Islands, for the presence of human adenoviruses (HAdV) using a polymerase chain reaction (PCR)-based typing assay. A total of 34 of these strains were found to be positive for adenovirus belonging to four different HAdV serotypes (HAdV-1, 2, 8, and 37). We found that HAdV-2 was the most frequently encountered serotype amongst the Acanthamoeba strains, and their identification was confirmed by a nested PCR specific for this serotype. We showed that Acanthamoeba genotype T4 was highly associated with serotype HAdV-2, whereas Acanthamoeba genotype T3 was most often associated with adenovirus serotypes related to ocular diseases. Based on these data, we suggest that Acanthamoeba should be considered as a potential reservoir and perhaps even a transmitter of adenoviruses to human and other secondary hosts.

Acanthamoeba keratitis due to Acanthamoeba genotype T4 in a non-contact-lens wearer in Turkey

An otherwise healthy 22-year-old man presented with Acanthamoeba keratitis (AK) in the right eye. He was not a contact lens wearer and had no history of corneal trauma. The Acanthamoeba strain isolated from a corneal scraping was identified as morphological group II and genotype T4. Three more Acanthamoeba strains isolated from sites of possible human contact with acanthamoebae in the same geographical region, including a lens storage case, tap water and soil, were subjected to morphological and molecular biological identification. Whereas the strain from tap water also exhibited genotype T4, the two other isolates were identified as morphological group I and genotype T9. To the best of our knowledge, this is the first study identifying an AK-causing Acanthamoeba strain in Turkey and the first isolation of genotype T9 in this country.

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.

Genotypic identification and species names in Acanthamoeba: correlation and conflict

Many named isolates of Acanthamoeba, e.g. isolates designated Acanthamoeba polyphaga, are used widely in studies of pathogenicity, and other biological characters. However, molecular analyses show that isolates designated A. polyphaga are polyphyletic. Isolates may be very dissimilar at the molecular level, but share a species name, leading investigators to believe that they should share biological characteristics. Here, we present a summary of the correlation in Acanthamoeba between genotypes and the named species of this genus. Analyses of sequences of the nuclear small subunit ribosomal RNA gene (ssu rDNA) have identified at least fifteen genotypes of the free‐living ameba genus Acanthamoeba. Genotype determination has been defined by a sequence dissimilarity of five percent or greater in pairwise sequence comparisons. The ssu rDNA genotypes correlate well with many of the named species of Acanthamoeba. However, in some cases a species name exists as an invalid synonym of other species names within monophyletic genotypic clades. In addition, numerous species names are associated with the large and widely distributed Acanthamoeba genotype T4. Using molecular examination, some of these species designations are shown to be polyphyletic. The genotypes identified by nuclear ssu rDNA are supported by the addition of data from the mitochondrial ssu rDNA, which also provide some resolution of clades within genotype T4. Some lineages within the T4 genotype are associated with named species. Robust identification of Acanthamoeba isolates, including molecular data such as genotypic designation, is required so that data from studies on physiology or pathology may be correctly interpreted.