Author: Harriet Whiley
Whiley, Harriet, 2015 Legionella spp., L. pneumophila and Mycobacterium avium complex (MAC) in potable and reuse water distribution pipelines., Flinders University, School of the Environment
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Legionella spp. and Mycobacterium avium complex (MAC) are opportunistic human pathogens of public health concern. The clinical manifestations of Legionella include Pontiac fever, an acute febrile illness, and Legionnaires disease, a severe atypical pneumonia. L. pneumophila is the most common causative agent of Legionellosis. In Australia, MAC is not a nationally notifiable disease, but it is responsible for a wide spectrum of illness dependent on subspecies, route of infection and a patient's pre-existing conditions. This includes, but is not limited to, a range of respiratory, gastrointestinal and cutaneous infections. Evidence also suggests that MAC is a causative agent of Crohn's disease. This study investigated the presence of Legionella spp., L. pneumophila and MAC along South Australian potable and reuse water distribution pipelines using qPCR. Two potable water distribution systems were chosen (one chlorine disinfected and the other chloramine disinfected) and two reuse water distribution systems (one utilising recycled wastewater treated with chlorine and UV disinfection and the other recycled wastewater combined with reclaimed stormwater treated with chlorine disinfection only). Samples were collected along each of the pipelines throughout the year, to determine any seasonal variation. Relationships between temperature, chlorine or chloramine residual, indicator bacteria, distance from treatment plant and concentration of Legionella and MAC was explored. Legionella spp., L. pneumophila and MAC were detected in both potable water distribution systems throughout the year. Maximum concentrations detected were 10^3 copies/mL in the chlorine disinfected system and 10^6, 10^3 and 10^4 copies/mL respectively in the chloramine disinfected system. The concentrations of these opportunistic pathogens were primarily controlled throughout the distribution network through the maintenance of disinfection residuals. At a dead-where the disinfection residual was not maintained significant (P[<]0.05) increased numbers of Legionella spp., L. pneumophila and MAC were observed when compared to the concentration measured closest to the processing plant in the same pipeline and sampling period. In the reuse water distribution systems Legionella spp., L. pneumophila and MAC were detected using qPCR at maximum concentrations of 10^5, 10^3 and 10^5 copies/mL respectively. During the summer period of sampling the concentration of all three organisms significantly (P[<]0.05) increased along the pipeline, suggesting multiplication and hence viability. No seasonality in the decrease in chlorine residual along the pipelines was observed. This suggests that the combination of reduced chlorine residual and increased water temperature promoted the presence of these opportunistic pathogens.
Keywords: Legionella,Legionella pneumophila,Mycobacterium avium,Mycobacterium avium complex,Nontuberculous mycobacteria,potable water,reuse water,distribution system,pipelines,risk assessment,qPCR
Subject: Environmental Science thesis
Thesis type: Doctor of Philosophy
School: School of the Environment
Supervisor: Professor Howard Fallowfield