Detection of legionella species and other microbiological and physicochemical Properties in natural and man-made water systems in the Colombo District

Abstract

𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 is a gram negative, aerobic, flagellated rod shaped bacterium found in aqueous environments, and exists as free living plankton, as an intracellular parasite in some free-living amoeba and as inhabitants of biofilms. Forty eight species of 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 have been discovered so far, of which 21 are pathogenic to human. Occurrence of 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 spp., in cooling towers in Sri Lanka has been previously recorded. However, there is no information regarding the prevalence of this bacterium in environmental sources. Therefore, the objective of this study was to evaluate the occurrence of 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 spp., in natural and man made water systems. Thirty six water and biofilm samples were collected to cover six different types of water sources from various parts in the Colombo district. They were decorative water features, domestic water supplied by wells, domestic water supplied by municipal, domestic hot water (initial supply from wells or municipal) and natural water bodies. Samples were analyzed by standard culture methods (ISO 11731:1998E) for 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 sp. The colonies which grew on BCYE but failed to grow on blood agar, were regarded as 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢, and further confirmed serologically by latex bead agglutination. Simultaneously, water samples were also assessed for aerobic plate counts (SLS 516 part 1: 1991, AMD 371), total coliform and Escherichia coli (SLS 614 part 2: 1983) and physicochemical properties, viz; turbidity, pH, colour, odour, temperature, free chlorine, electrical conductivity, iron and total hardness (SLS 614: part 1). Algae were detected microscopically. The results indicated that 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 spp. were not present in detectable numbers in natural and man made water systems that were investigated in the current study. However, the natural water bodies were contaminated with total coliforms, in the range of 900-1800 MPN per 100 ml, while 60% of domestic water systems supplied by well water was faecally contaminated (𝘌𝘴𝘤𝘩𝘦𝘳𝘪𝘤𝘩𝘪𝘢 𝘤𝘰𝘭𝘪) in the range of 5-80 MPN per 100 ml. Domestic water systems supplied by municipal water was free of total coliforms and 𝘌. 𝘤𝘰𝘭𝘪. Algae (𝘊𝘩𝘭𝘰𝘳𝘦𝘭𝘭𝘢, diatoms, 𝘜𝘭𝘰𝘵𝘩𝘳𝘪𝘹, 𝘗𝘦𝘥𝘢𝘴𝘵𝘳𝘪𝘶𝘮, 𝘕𝘦𝘵𝘳𝘪𝘶𝘮, 𝘡𝘺𝘨𝘯𝘰𝘮𝘢, 𝘌𝘶𝘥𝘰𝘳𝘪𝘯𝘢, 𝘈𝘯𝘢𝘤𝘺𝘴𝘵𝘪𝘴, 𝘚𝘱𝘪𝘳𝘰𝘨𝘺𝘳𝘢 and some unidentified alga) were detected in decorative water features and natural water bodies while they were not detected in municipal and well water. All physicochemical parameters investigated were within the permissible levels other than pH levels of well water, which were in the range of 4.4 - 5.8 and the high turbidity of natural water bodies and decorative water features. According to the current study it can be concluded that 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 spp. is not an environmental threat in the Colombo district. Several biotic and abiotic factors such as high aerobic plate counts, absence of algae and protozoa, low electrical conductivity levels and iron in water may be contributory to the non detectable levels of 𝘓𝘦𝘨𝘪𝘰𝘯𝘦𝘭𝘭𝘢 in the water samples analyzed in the current study.