Free-Living Amoebae in Soil Samples from Santiago Island, Cape Verde

Abstract

Free-Living Amoebae (FLA) are widely distributed protozoa, which contain some groups considered as pathogenic microorganisms. These members are able to produce several opportunistic diseases including epithelial disorders, such as keratitis and fatal encephalitis. Even though they have been reported in numerous sources, such as soils, dust and water, there is no legislation related to the presence of these protozoa in soil-related environments worldwide. Therefore, there are no established prevention or disinfection protocols to advise the population regarding FLA infections or eliminate these microorganisms from human-related environments to date. Acanthamoeba spp. are the most common FLA isolated in soil samples, which is also the most common genera found in clinical cases. Thus, the aim of the present study was to evaluate the presence of potentially pathogenic FLA in human-related soil samples of Santiago Island, Cabo Verde. A total of 26 soil samples were seeded in non-nutrient agar plates (2%), incubated at 26 °C, and monitored daily to evaluate the presence of FLA. DNA was extracted from those plates on which there was suspected FLA growth, and PCR amplification of the 18S rRNA gene was carried out. A total of 17 from the 26 analysed samples were positive for FLA, where Acanthamoeba is the most abundant isolated genus (14/17; 82.4%), with the T4 genotype being the most common (13/14; 92.9%), followed by the T5 genotype, A. lenticulata (1/14; 7.1%). Moreover, Vermamoeba vermiformis, Stenamoeba dejonckheerei and Vannella pentlandi were isolated in three other samples. To the best of our knowledge, this is the first report of FLA presence in Cape Verde and the first report of V. vermiformis in beach sand worldwide.