Prevalence of Free-Living Amoebae in Tap Water and Biofilm, Egypt

Free-living amoebae are protozoa found in soil and water. Among them, some are pathogenic and many have been described as potential reservoirs of pathogenic bacteria. In the present work, a total of 48 tap water samples were collected from Giza governorate, Egypt. Samples were processed for detection of free-living amoebae using non-nutrient agar (NNA) and were incubated at 30 degrees C. The isolates of free-living amoebae were identified morphologically and molecularly to the genus level. Members of genus Acanthamoeba were identified to species level based only on the morphologic criteria. The obtained results showed that free-living amoebae were found in 60.4% of the examined tap water samples. Concerning seasonal variation, the highest occurrence percentage of free-living amoebae in water samples was observed in summer season (75%), and then it decreased to be 66.7, 58.3 and 41.7% in autumn, spring and winter, respectively. Morphological identification and molecular confirmation of the isolated free-living amoebae revealed the presence of 4 genera namely Acanthamoeba spp., Naegleria spp, Vermamoeba (Hartmannella) and Vannella spp. The formed biofilm inside the sampled drinking water pipe lines contained only Acanthamoeba and Vannella spp. In conclusion, the appearance of free-living amoebae especially potentially pathogenic amoebae in tap water might represent a significant threat to public health.