Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Parasitology

Free living amoebae are ubiquitous in nature. Some species of FLA belonging to the genera Acanthamoeba and Naegleria are responsiple for opportunistic and non-opportunistic infections in humans. This study was conducted for the isolation and molecular characterization of FLA obtained from different water sources and to address the occurrence of FLA in water sources as a potential risk for human health. This cross sectional study was carried out on 120 water samples collected from different water sources including Nile River, tap and swimming pool water samples in Giza governorate, Egypt. The water samples were collected from 30 fixed places during the four different seasons to assess seasonal variability of FLA. Each Water sample was filtrated and transferred to non-nutrient agar(NNA) plates seeded with a suspension of Escherichia coli and incubated for 14 days at 37{u00B0}C. The plates were examined by microscopy to morphologically identify FLA families, and PCR and sequence analysis were then performed to define the species of the detected Naegleria and Acanthamoeba isolates. FLA were found in 77 (64.2%) of the investigated water samples. Nile water and tap connected to tank water were the sources with higher prevalence rates(100% for both).Identification of FLA species/genotypes, based on the 18S r DNA regions, allowed to identify four different Acanthamoeba genotypes(T4, T9, T11and T15) with T9 being reported for the first time in Egypt and genetically distinct isolates of Naegleria including N.australiensis, N. philippinensis, N.neojejuensis and Vahlkampfia ciguana, this is the first study that reports the prescence of these Naegleria isolates in Egypt. N. fowleri,previously reported in Egypt,was not recovered in the present study

Issued also as CD