Free-living amoebas of the genus Acanthamoeba are ubiquitous, amphizoid protozoans widely distributed in nature. They have been isolated from both aquatic and terrestrial natural environments and from human habitats. They are opportunistic pathogens in humans, causing severe conditions with high morbidity and mortality. They can also act as a reservoir for microorganisms of public health importance. Acanthamoeba spp. remains viable at temperatures between 25°C and 35°C, but little information exists regarding their viability at low temperatures. The objective of this study was to determine the survival rate of different strains of Acanthamoeba spp. under continuous incubation at freezing temperatures of -5°C and freezer temperatures of -20°C. Three strains of Acanthamoeba spp were used: Acanthamoeba polyphaga ATCC 30461, Acanthamoeba spp. isolated in a closed ward of a pediatric hospital and Acanthamoeba spp. recovered from a coastal wetland in southeastern Buenos Aires. The strains were subjected to freezing (-5 ° C) and freezer (-20 ° C) for 30, 120 and 270 days. Growth and viability controls of cysts post exposure and morphological identifications were performed in fresh, subcultures and special staining. The results revealed that 100% of the Acanthamoeba spp strains used in this study remained viable for 30, 120 and 270 days at both -5 ° C and -20 ° C, evidencing the resistance of the protozoan cysts to freezing. The results obtained have significant implications for environmental microbiology, public health, and epidemiological surveillance of infectious diseases.
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