Acanthamoeba of three morphological groups and distinct genotypes exhibit variable and weakly inter-related physiological properties
Name: CYNARA OLIVEIRA POSSAMAI
Publication date: 21/03/2018
Advisor:
Name |
Role |
|---|---|
| ALOÍSIO FALQUETO | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| ALOÍSIO FALQUETO | Advisor * |
| BLIMA FUX | Internal Examiner * |
| GUSTAVO ROCHA LEITE | External Examiner * |
| RAQUEL SPINASSÉ DETTOGNI | External Examiner * |
| SARAH GONCALVES TAVARES | Internal Examiner * |
Summary: Free living amoeba of the genus Acanthamoeba can eventually act as parasites, causing severe infections in humans and other animals. Some biological and physiological characteristics have been related to the grade of pathogenicity of strains, allowing inferences about the pathogenic potential of the genera. The main goal of this study was to classify isolates of Acanthamoeba obtained in Brazil, evaluate properties associated with their pathogenicity and discuss the results in association with the origin of the isolates. A total of 39 Acanthamoeba isolates obtained from amoebic keratitis cases (n=16) and environmental sources (n=23) were classified into morphological groups (I, II, III) and genotyped (T1-T20) by sequencing the 18S rDNA fragments ASA.S1 and GTSA.B1. Samples were also tested regarding their thermotolerance, osmotolerance and cytopathogenicity in MDCK cells. Comparisons of clinical and environment isolates were performed by x2 test (p<0,05). Isolates were classified as follows: group I (T17, T18); group II (T1, T3, T4, T11); and group III (T5, T15), with the predominance of genotype T4 (22/39). Clinical isolates were genotyped as T3 (1/16), T4 (14/16) and T5 (1/16). The majority of isolates (38/39) were able to grow at 37 °C, but tolerance to 40 °C was more frequent among environmental samples. The tolerance to 1 M mannitol was infrequent (4/39), with three of these corresponding to clinical samples. There was no significant difference between the numbers of clinical and environmental isolates that presented tolerance to 40 C (p=0,06), to 1 M mannitol (p=0,14) and ability to cause cytopathic effects (p=0,59). Variable correspondence of these properties was observed among distinct genotypes. This study identified, for the first time, the genotypes T1, T15 and T18 in Brazil. It also indicated a weak association between the clinical origin of the isolates and physiological tolerance tests and cytopathogenicity, demonstrating that some in vitro parameters do not necessarily reflect a higher propensity of Acanthamoeba to cause disease.
