Pseudomonas Aeruginosa: Assessment of Risk from Drinking Water

The Issue

Pseudomonas aeruginosa is a bacterium that is naturally found in many types of drinking water. For example, it is a violation of European regulations to have Pseudomonas aeruginosa present in a 250 ml sample of bottled water. However, no such regulation exists in the United States. Apparently, the Pseudomonas aeruginosa regulation in Europe originated as a quality control issue and not as a health effects issue. During the last decade, a number of papers have appeared that have indicated that Pseudomonas aeruginosa from drinking water is a health threat. However, it is not considered a health threat by those in the clinical microbiology or infectious diseases communities. Therefore, an assessment of health risk to humans from Pseudomonas aeruginosa from drinking water was conducted.

Research Strategy

A practicing infectious disease physician (Dr. Catherine Hardalo, Yale University) and a medical microbiologist (Dr. Stephen Edberg, Yale University) collaborated to perform the health risk analysis of Pseudomonas aeruginosa from drinking water. An extensive literature search was conducted and colleagues were consulted.

Major Findings and Significance

Pseudomonas aeruginosa is a ubiquitous environmental bacterium. It can be recovered, often in high numbers, in common food, especially vegetables. Moreover, it can be recovered in low numbers in drinking water. A small percentage of clones of Pseudomonas aeruginosa possess the required number of virulence factors to cause infection. However, Pseudomonas aeruginosa will not proliferate on normal tissue but requires previously damaged organs. Further narrowing the risk to human health is that only certain specific hosts are at risk, including patients with profound neutropenia, cystic fibrosis, severe burns, and those subject to foreign device installation. Other than these very well defined groups, the general population is refractory to infection with Pseudomonas aeruginosa. Because of its ubiquitous nature it is not only impractical to eliminate Pseudomonas aeruginosa from our food and drinking water but attempts to do so would produce disinfection byproducts more hazardous than the species itself. Moreover, because there is no readily available sensitive and specific means to detect and identify Pseudomonas aeruginosa available in the field, any potential regulation governing its control would not have a defined laboratory test measure of outcome. Accordingly, attempts to regulate Pseudomonas aeruginosa in drinking water would not yield public health protection benefits and could, in fact, be counterproductive in this regard.

Hardalo, C. and Edberg, S.C., Pseudomonas aeruginosa: Assessment of Risk from Drinking Water, Critical Reviews in Microbiology, 23(1):47-75 (1997).