Opportunistic Pathogens in Drinking Water Distribution Systems-A Review

Area of Science:

• Environmental microbiology
• Water quality and treatment
• Public health

Background:

• Drinking water treatment historically focused on "frank" pathogens.
• Increasing outbreaks are linked to opportunistic pathogens in drinking water.
• Opportunistic pathogens thrive in biofilms, resist disinfectants, and amplify in distribution systems.

Purpose of the Study:

• To review the public health risks of opportunistic pathogens in drinking water.
• To detail occurrence, disinfectant susceptibility, and management practices for key opportunistic pathogens.
• To address the growing challenge of opportunistic pathogens in drinking water systems.

Main Methods:

• Focus on common opportunistic pathogens: Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa.
• Includes information on nine other less common opportunistic pathogens.
• Discusses factors influencing microbial growth in distribution systems (temperature, disinfectant, nutrients, stagnation).

Main Results:

• Legionella pneumophila has well-established risks and management guidelines.
• Mycobacterium avium is difficult to treat due to disinfection resistance and biofilm formation.
• Management practices for L. pneumophila, such as maintaining disinfectant residual and flushing, benefit control of other opportunistic pathogens.

Conclusions:

• Controlling opportunistic pathogen growth, particularly in biofilms within distribution systems, is crucial.
• Climate change may exacerbate factors driving opportunistic pathogen growth.
• Evaluating and enhancing treatment barriers and management activities are essential for risk reduction.