Microbial and Physico-chemical Characteristics Associated with the Incidence of Legionella spp. and Acanthamoeba spp. in Rainwater Harvested from Different Roofing Materials

The incidence of Legionella and Acanthamoeba spp. was correlated to microbial indicator analysis and physico-chemical characteristics of rainwater harvested from catchment areas constructed from galvanized zinc, Chromadek®, and asbestos, respectively. Quantitative PCR (qPCR) analysis indicated that no significant difference (p > 0.05) in copy numbers of Legionella spp. and Acanthamoeba spp. was recorded in tank water samples collected from the respective roofing materials. However, significant positive Spearman (ρ) correlations were recorded between the occurrences of Legionella spp. gene copies vs. nitrites and nitrates (p = 0.05) in all tank water samples. Significant positive correlations were also established between Acanthamoeba spp. vs. barium (p = 0.03), magnesium (p = 0.02), sodium (p = 0.02), silicon (p = 0.05), arsenic (p = 0.03), and phosphate (p = 0.01), respectively. Additionally, while no significant correlations were observed between Legionella spp. vs. the indicator bacteria (p > 0.05), positive correlations were observed between Acanthamoeba spp. vs. total coliforms (p = 0.01) and Acanthamoeba spp. vs. Escherichia coli (p = 0.02), respectively. Results obtained in the current study thus indicate that the incidence of Acanthamoeba and Legionella spp. in harvested rainwater was not influenced by the roofing material utilized. Moreover, it is essential that the microbial quality of rainwater be assessed before this water source is implemented for potable and domestic uses as untreated harvested rainwater may lead to legionellosis and amoebae infections.