Occurrence and Mitigation of Opportunistic Drinking Water Pathogens in Large Building Water Systems

«Drinking water is recognized as a significant source of waterborne infections when opportunistic pathogenic bacteria are present, such as Legionella pneumophila (Lp), Pseudomonas aeruginosa (Pa), and nontuberculous mycobacteria (NTMs). These bacteria pose major public health concerns when they proliferate in water systems, particularly within biofilms that adhere to the internal surfaces of plumbing pipes and fixtures. Unlike frank pathogens, these opportunistic bacteria do not cause severe diseases in healthy individuals, but they can lead to acute, sometimes fatal, infections in immunocompromised populations, the elderly, and those with chronic illnesses. • Legionella pneumophila is responsible for the majority of Legionnaires’ disease cases in Europe/North America, a severe form of pneumonia-like infection transmitted by inhaling contaminated aerosols. Although most cases are community-acquired or travel-related, nosocomial infections impose a disproportionate health burden due to their severity and the vulnerability of the populations involved. • Pseudomonas aeruginosa causes numerous hospital-acquired infections, especially among burn victims and cystic fibrosis patients. A recent European study found that 31% of strains were resistant to at least one group of antibiotics, therefore complicating treatment efforts. • Nontuberculous mycobacteria are a diverse group that can cause chronic pulmonary diseases, as well as skin and soft tissue infections, with an alarmingly increasing incidence rate globally. They are also linked to the highest number of investigations into water-related nosocomial infections in the United States. Given these concerning trends, managing water systems in large buildings has become a complex, but crucial challenge. These systems feature heterogeneous conditions of operation, design, and usage, thus creating environments conducive to the growth and dispersal of microorganisms. Despite these challenges, regulations and practices specific to managing building water systems remain limited or inconsistent. The primary goal of this research project is to provide evidence-based recommendations to improve the monitoring, operation, and design of plumbing systems in large buildings. By combining novel tools, this research aims to study the occurrence of opportunistic pathogens (OPs) (Lp, Pa, NTMs) and assess the effectiveness of preventative and corrective measures designed to reduce users’ exposure risks. This thesis also seeks to inform building managers of their duty of diligence by suggesting practical solutions for proactive management of their buildings’ water systems.»