The occurrence of free-living Amoebae and Amoeba resistant bacteria in drinking water of Johannesburg City, South Africa

M.Tech. (Biomedical Technology)Drinking water in the greater Johannesburg area is produced by Rand Water and is transported to local Johannesburg Water where it is stored in reservoirs for distribution. At any point during the production, distribution and storage of the water, contamination with free-living amoebae, potentially containing amoeba resistant bacteria, may occur. Free-living amoebae are often resistant to the biocides used by water treatment industries and may thus be transmitted to public facilities, consumers’ homes and informal settlements through water distribution systems and during storage in small containers. The aim of our study was to analyse the water quality around Johannesburg with regard to free-living amoebae and amoeba resistant bacteria. A total of 182 tap and 5 storage tank water samples, collected from Hillbrow, Bertrams, Riverlea, Braamfischerville and Hospital Hill, were analysed for amoebae, indicator organisms, Legionellae, environmental mycobacteria, Shigella, Salmonella and Vibrio species using amoebal enrichment method. Direct microscopy indicated the presence of amoebae in 96.1% of samples. Acanthamoeba cysts were present in 69.0% of the samples. In 55.0% of these samples visibly active intracellular bacteria were observed within the sample suspensions. In the 46 samples analysed by polymerase chain reaction, the presence of Acanthamoeba species was confirmed in 65.2%, and the intracellular bacteria such as Legionella pneumophila and Mycobacterium avium was confirmed in 23.9% and 73.9% respectively. All samples indicated the presence of Shigella species while one sample contained Salmonella species on xylose lysine desoxycholate agar after amoebal enrichment processing. Vibrio species was not confirmed in the samples. Our results indicated a high risk of transmission of amoeba resistant bacteria through drinking water to people living in these areas