Legionella in the City: Unveiling Legionella pneumophila in Hillbrow's High-Rise Water Systems

Urban settings in developing countries present unique challenges such as high population density, inadequate water infrastructure and water supply, all factors that contribute to the growing threat of premise plumbing pathogens such as Legionella. Water droplets from showers and faucets aerosolise Legionella, which, when inhaled, invade the human respiratory tract to manifest as Legionnaires' disease. Densely populated, high-rise buildings present an ideal case study for investigating the presence of Legionella. The aim of this study was to investigate the occurrence of Legionella pneumophila (L. pneumophila) in water systems of 15 high-rise buildings in Hillbrow, Johannesburg, South Africa. A total of 67 hot- and cold-water samples and 121 swab samples were collected and analysed for the presence of Legionella pneumophila. Samples were analysed using the Legiolert assay, the South African National Standard (SANS) 11731:2017 method, and the amoeba enrichment method for detecting amoeba-associated Legionella. Molecular confirmation of the pathogen was conducted using conventional PCR and quantitative real-time PCR targeting the mip gene. Legionella pneumophila was found in 93% (14/15) of the buildings that were sampled and was more prevalent in cold-water samples (65%) compared to warm-water (35%) samples. All buildings were positive (100%) for the growth of free-living amoeba (FLA) from water and swab samples. Of these samples, three were confirmed positive for L. pneumophila by PCR and the sequencing alignment results confirmed the identity and relatedness of the isolates to L. pneumophila.