Resumo

Free-living amoebae (FLA) of Acanthamoeba genus are among the most abundant and widely distributed protozoa in the environment. They have been isolated from soil, saltwater, freshwater, air samples and from all over the world, which confers to the genus a great biological and ecological importance. Furthermore, it can be considered an important vehicle of human pathogens like Legionella pneumophila, Mycobacterium avium, and other “amoeba-resistant microorganisms” like viruses and fungi. The phylloplane is considered an important habitat for a wide variety of microorganisms, however it ecological relationships requires further investigation. The main aim of the current study was to identify the presence of FLA in the phylloplane of bromeliads in Southern Brazil. Ten samples of the surface bromeliads leaves were collected with swabs. The swabs were placed in sterile tubes containing 50 ml of sterile distilled water, gently shaken, squeezed and discarded. The material stayed under sedimentation process for 2 hours. Then, centrifugation was performed at 250 x g for 10 minutes. The supernatant was discarded and the sediment resuspended in 0.5 ml of saline page. Then, 100 ml of this suspension was used as inoculum plate of 1.5% non-nutrient agar (NNA) containing an overlayer of an Escherichia coli (ATCC25922) suspension heat inactivated (for 2 h at 56 °C), incubated at 30 °C and for 10 days. Nine (90%) of the leaves samples investigated were found positive for free-living amoebae, all identified as belonging to Acanthamoeba genus. All nine isolates were positive in the Acanthamoeba-specific PCR that amplify the ASA.S1 region of 18S rDNA gene. The isolates are in molecular identification and genotyping process. Physiological tests of thermotolerance and osmotolerance were used to evaluate the pathogenicity of the isolates. All Acanthamoeba isolates investigated grew at 37 °C and with 0.5 M mannitol. The results of this first study on the identification and characterization of Acanthamoeba in the phylloplane of bromeliads leaves in Southern Brazil confirm the presence of potentially pathogenic types that may present a risk to human health and ubiquity of the Acanthamoeba genus, which are distributed in the natural and artificial environment sources. Financial support: CNPq and CAPES.