From the editor:
This is the 14th post in an ongoing series profiling microorganisms of particular significance in water and wastewater systems. In this series we will cover microorganisms of many types including some that are beneficial, inhibitory and pathogenic.
Pseudomonas is a genus of Gram-negative, rod shaped, non-spore forming bacteria. More than 190 species have been identified and exist widely throughout the environment including in soil, water, plants, and feces. Notable species include Pseudomas putida, the first genetically modified organism to be patented, thanks to its ability to biodegrade oil spill contamination, and P. aeruginosa, an opportunistic pathogen that is often associated with hospital acquired infections.
P. aeruginosa is likely the most well-known species, because of its ability to cause severe infections in people with compromised immune systems. The bacteria can be found in a range of settings, including soils, plants, animals, humans, and indoor settings. They can persist in places like hospitals because of their ability to survive in low-nutrient conditions. Infections can be difficult to treat, because P. aeruginosa can develop resistance to a variety of antibacterial agents. The bacteria obtain resistance from having a cell wall with relatively low permeability and through having the ability to pump out the antibacterial agent before it has a chance to take effect. According to the World Health Organization, the most common route for infection is through contact between susceptible tissue, which might include burns and wounds, and contaminated water or medical equipment. Therefore, to prevent infections, health-care facilities typically provide additional water treatment or sterilization to limit or eliminate the presence of the bacteria.
CDC estimates P. aeruginosa causes more than 50,000 healthcare-related outbreaks in the US each year, with more than 10% of the cases involving multi-drug resistant strains and as many as 400 cases that are fatal. P. aeruginosa is also responsible for a large number of milder infections on an annual basis, often through exposure to recreational waters, such as pools and hot tubs, causing conditions known as “Hot Tub Rash” and “Swimmer’s Ear.”
Typical drinking water treatment and disinfection practices are relatively effective at inactivating the bacteria in planktonic form. Unfortunately, because the bacteria are so widespread, it is nearly impossible to entirely eliminate them from distribution and domestic water systems, as this would require such high levels of disinfectant that health risks associated with disinfection byproducts would actually outweigh the risks from the bacteria. Consequently, P. aeruginosa can become embedded in biofilms in distribution systems or premise plumbing, where they’re sheltered from disinfectants and are capable of amplification. Therefore, levels of P. aeruginosa are typically controlled by reducing microbiological growth in general and preventing biofilm formation. This is often accomplished by maintaining an adequate disinfectant residual and optimizing organic carbon removal processes.
Another key component for preventing microbiological growth is to implement an effective and reliable microbiological monitoring program to verify that treatment strategies are effective and that microbial levels are acceptable. If you are interested in learning how ATP can be used for monitoring microbial growth in premise plumbing in healthcare facilities, be sure to check out our two case studies below: