Legionella Amplification

Legionella bacteria can be amplified or incubated to the point where the bacteria multiplies when the right conditions are present. The legionella growth range has been identified in laboratory testing to show that Legionella bacteria will grow at temperatures between 68 and 122 degrees Fahrenheit. Legionella bacteria has an ideal growth range where it reproduces at an accelerated rate between 95 and 115 degrees Fahrenheit (Diagram 1 – How Legionella Bacteria Responds to Water Temperatures ).

Amplification Sources

There are many sources in a building water system that can contribute to amplification of Legionella bactera that is commonly present, in small amounts, in a building water distribution system. Municipal water systems typical introduce chlorine or mono-chlorines to minimize bacteria in the public water supply. Small amounts of organic pathogens, including Legionella, can be introduced into a building water distribution system and the amounts of bacteria can vary from one time of the year to another. There are three common factors that can contribute to increases of Legionella in the water supply. The three factors are water temperatures in the ideal growth range, stagnation and mineral build-up or biofilm in the piping. Stagnation allows the chlorine to dissipate and the warm temperatures create an environment for Legionalla growth on the biofilm on the walls of the pipes or equipment.

Contributing Sources of increased bacteria counts

1) Water Main Construction – Water main construction can dislodge bacteria in the biofilm and mineral build-up on the walls of the water mains. One way to minimize large doses of Legionellae from being introduced a duplex catridge type filter into the piping system, at the meter. The filter can then catch the debris and organisms that Legionellae can feed off of.

2) Warm environment -A warm environment can leave the piping systemslide2-2 valves, tanks, etc in the ideal growth range for Legionellae. Many pipes and equipment are located in spaces or environments that are in the idea growth range for Legionellae. When these piping systems are in the ideal growth range, they should be circulated or treated to minimize the bacteria growth.

Other Legionella Facts

  • Legionella is the name of a bacterium that is found primarily in warm water environments. Legionella cause Legionnaires' disease, a multisystem illness that includes a deadly type of pneumonia. Both disease and the bacterium were discovered following an outbreak traced to a 1976 American Legion convention in Philadelphia.
  • Many if not most cases of nosocomial (hospital acquired) Legionnaires' disease go undetected, and most detected cases are not reported. Therefore, many health care professionals have the false impression that Legionnaires' disease is rare, but it is actually widespread.
  • Legionnaires' disease is contracted by inhaling water droplets containing Legionella. Some investigators believe that the disease may be acquired also by drinking Legionella contaminated water, particularly if Legionella aspirated from the water are inhaled before the water enters the stomach.
  • Underlying disease and advanced age not only increase the risk of contraction Legionnaires' disease but also the risk of dying from it. Thus the death rate for nosocomial cases is higher than the death rate for community acquired cases.
  • Outbreaks have been linked to domestic water systems, cooling towers and evaporative condensers, respiratory care equipment, showers, faucets, whirlpool baths, humidifiers, decorative fountains and a grocery store mist machine. The hot-water system and cooling towers are the primary sources to be addressed by health care facility managers.
  • The hot-water system can be a perfect breeding habitat for Legionella. Legionella grow best in water at 35°C to 46°C. Scale and biofilm within tanks, pipes and fixtures add to the problem by providing food and protection for Legionella.
  • In most cases for a healthy human being, contracting Legionnaires' disease has a low risk. However, there is a general estimate of Legionella per ml ratio that can help you know what procedures need to be taken
  • At very low levels, Legionella bacteria is not a concern. As the concentration increases, the potential for incubation in warm or hot water piping systems.
  • Water pressure shock, major excavation work and the opening of new or renovated buildings have dislodged biofilm full of Legionella and caused Legionella outbreaks. These incidents may cause biofilm or sediments with high concentrations of Legionella to be released into water systems.
  • Numerous cases of Legionella outbreaks have been associated with excavation. Some experts believe that excavation causes the Legionella to release from soil and then can enter cooling towers, air intakes, water pipes or inhalation. Dust and dirt can also potentially provide a nutrient rich food source for existing Legionella in cooling towers or domestic water systems.
  • Water main construction has been known to release scale and biofilm with contain Legionella bacteria from the walls of old water mains. When high doses of Legionella are introduced into the water supply system and water storage temperatures are within the ideal growth range, it increases the risk of Legionella infection.
  • Plumbing systems in new buildings that are not flushed to remove dirt prior to opening can present Legionella problems. Idle buildings with stagnant water or hospitals that have sitting water due to renovation can increase the amounts of Legionella in the water systems.