Climate change and opportunistic pathogens (OPs) in the built environment

Abstract

Table 1: Characteristics of selected opportunistic pathogens (OPs) of concern in Canada.Legionella spp. Description: Gram-negative bacteria, found in natural water systems and soils, have been detected in most large building water systems and some 10%-30% of home water systems in the United States. Legionella bacteria can be present in water storage containers, pipes, or outlets. Optimal growing conditions: Preference for warm water (e.g., 25-45 °C), high water age, low disinfectant residual, and often associated with biofilms or free-living amoeba (FLA). Routes of transmission: Inhalation or accidental aspiration of aerosolized contaminated water droplets into the lungs from faucets, showerhead, water misters, decorative fountains, hot tubs, cooling towers, etc. Outcome of infection: Legionellosis, includes Legionnaires' disease (LD), a severe pneumonia with a fatality rate of about 10%, and Pontiac fever, a milder flu-like illness. L. pneumophila is the cause of most cases of LD. Groups most at risk: Smokers, over-50s, men, immune-compromised persons, and those with conditions like chronic obstructive pulmonary disease, coronary artery disease, dementia, diabetes, kidney disease, and neurological diseases. Pseudomonas spp. Description: Gram-negative bacteria that can form or join biofilms and colonize plumbing. Found in building water system at point of use areas (e.g., faucets, drains, and showerheads) more often than distribution systems, and can colonize humidifiers, respiratory equipment, swimming pools, hot tubs, and water baths. Optimal growing conditions: Tolerate a range of temperatures (4-42 °C), with an optimum around 37 °C, and reduced virulence below 30 °C; optimal pH around 7.2 and tolerate low dissolved oxygen, low nutrient, and stagnant waters. Grow well in poorly disinfected systems, but also resist disinfectants and can survive in FLA. Routes of transmission: Direct ear and skin contact in swimming pools, hot tubs, and whirlpools; inhalation of aerosols dispersed from faucets, showerhead, etc.; indirect transfer from contaminated devices or fomites. More commonly found in plumbing fixtures than in distribution systems. Outcome of infection: Most infections (80%) associated with P. aeruginosa and P. maltophila range from minor eye, skin, and ear conditions (e.g., swimmer's ear), to bacteremia in immune-compromised individuals or other susceptible patients. A major cause of healthcare-acquired pneumonia, wound infections, and urinary tract infections, and a cause of morbidity and mortality for cystic fibrosis patients. Groups most at risk: Children with cystic fibrosis, hospitalized patients at risk of hospital-acquired pneumonia, newborns, burn patients, patients with invasive devices, and those with underlying pulmonary disease. Nontuberculous mycobacterium (NTM) Description: NTM are a group of more than 190 known species of OP found in natural waters and soil, and building water systems. Includes Mycobacterium avium complex, a group of related bacteria that includes both M. avium and M. intrac...

Opportunistic Pathogens in Drinking Water Distribution Systems—A Review

“…L. pneumophila was detected in drinking water distribution systems only at temperatures greater than 18 • C [34]. In recent excellent reviews on the impact of climate change on opportunistic pathogens in water systems, O'Keeffe [35] and Blanc et al [36] provide evidence that increases in water temperature will increase the proliferation of Legionella spp., Mycobacterium spp., and other opportunistic pathogens. A pilot study by Calero-Preciado et al [37] demonstrated increases in opportunistic pathogens (M. avium, P. aeruginosa, Acanthamoeba, and S. maltophilia) in biofilm and water samples when water temperatures increased from 16 to 24 • C. O'Keeffe [35] notes that warmer temperatures would increase the use of cooling towers that could promote Legionella risk.…”

“…In recent excellent reviews on the impact of climate change on opportunistic pathogens in water systems, O'Keeffe [35] and Blanc et al [36] provide evidence that increases in water temperature will increase the proliferation of Legionella spp., Mycobacterium spp., and other opportunistic pathogens. A pilot study by Calero-Preciado et al [37] demonstrated increases in opportunistic pathogens (M. avium, P. aeruginosa, Acanthamoeba, and S. maltophilia) in biofilm and water samples when water temperatures increased from 16 to 24 • C. O'Keeffe [35] notes that warmer temperatures would increase the use of cooling towers that could promote Legionella risk. Increased water conservation efforts due to climate change would accelerate the adoption of water efficient devices that could indirectly promote the growth of opportunistic pathogens through increased water age and decreased disinfectant residuals [35].…”

“…A pilot study by Calero-Preciado et al [37] demonstrated increases in opportunistic pathogens (M. avium, P. aeruginosa, Acanthamoeba, and S. maltophilia) in biofilm and water samples when water temperatures increased from 16 to 24 • C. O'Keeffe [35] notes that warmer temperatures would increase the use of cooling towers that could promote Legionella risk. Increased water conservation efforts due to climate change would accelerate the adoption of water efficient devices that could indirectly promote the growth of opportunistic pathogens through increased water age and decreased disinfectant residuals [35]. Disease risk for some Mycobacterium species can be greater in warmer or tropical regions [36].…”

“…Cyanobacteria are extensively grazed by amoebae, and Naegleria (and other free-living amoeba) have been associated with cyanobacteria-dominated layers in a stratified lake [39]. Source water concentrations of L. pneumophila, B. pseudomallei, and other opportunistic pathogens can be expected to increase with warmer water temperatures associated with climate change [35,36,41].…”

Photodynamic Inactivation of Opportunistic Premise Plumbing Pathogens and Their Biofilms

“…According to some predictions, climate change will lead to more outbreaks of diseases caused by OPPPs, for example, due to greater use of air-conditioning systems, swimming pools, green infrastructure, etc. [54]. Therefore, new approaches and methods are needed in water disinfection and for the control and fight against OPPPs and their biofilms, and some of these approaches could be based on light-activated mechanisms and photoinactivation.…”