Legionella Bacteria

Artist representation of legionella bacteria under a powerful microscope.Legionella bacteria is the bacteria known to cause legionellosis or Legionnaires’ Disease. Legionella was first discovered in 1976 after an outbreak among people who became ill after an American Legion convention held in a hotel in Philadelphia. The people who were affected suffered from a type of severe pneumonia (lung infection) that eventually became known as Legionnaires’ Disease.

Legionnaires’ Disease is still a very big concern today. According to the Centers for Disease Control and Prevention (CDC), there are approximately 5,000 cases of Legionnaires’ disease reported in the United States each year. It is estimated that one out of every 10 people who get sick from Legionnaires’ Disease will die. Recently, during the summer of 2015, New York City had its worst outbreak in recorded history in which 16 people died and 133 people were sickened. New York City alleges that the source of the outbreak was an infected cooling tower located in the South Bronx.

In reaction to this tragedy, New York City and State have passed some of the most comprehensive cooling tower maintenance legislation in the United States, which has also shined a light on the liability associated with not having a plan for controlling Legionella in publicly accessed water systems. Soon property owners, investors and managers, as well as commercial, hospitality, healthcare and residential real estate developers may no longer be able to claim ignorance on the dangers of Legionella. For these groups, being proactive and having a plan is the first step in legionella prevention.

Identifying Legionella Bacteria

Legionella bacteria are easily identified under microscope by Gram staining.  Also called Gram’s method, it is a method of staining used to differentiate bacterial species into two large groups (Gram-positive and Gram-negative). The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique. In the Gram stain process, the cells are stained with a basic dye, known as crystal violet, which is taken up in similar amounts by all bacteria. The cells are then washed and then treated with a counterstain of a paler color, usually appearing as pink or red. Gram-positive organisms preserve the initial violet stain, while Gram-negative organisms are decolorized by the organic solvent used in the washing process and, as a result, show the pink counterstain. The difference between Gram-positive and Gram-negative bacteria lies in the ability of the organism’s cell walls to retain the crystal violet.

Legionella is a Gram-negative bacteria and, therefore, will appear as pink using Gram’s method. Other infamous Gram-negative bacteria include the organisms responsible for bacterial meningitis, cholera and the bubonic plague.

How does someone get Legionnaires’ Disease?Legionella bacteria colonies are amplified in manmade water systems.

Legionella is commonly found in soil and bodies of fresh water, like lakes and streams. In those environments they generally pose little threat because natural conditions (bacteria eaters, UV light, etc) help to keep their colonies at safe levels. Legionella becomes an issue when they infiltrate a manmade water system that presents the conditions necessary for amplification and aerosolization. Amplification happens when Legionella is allowed to grow unhindered in a warm, wet environment. If it has a food source, it multiples faster. If it is shielded from UV light, it multiples faster.

Aerosolization happens when the water that the legionella are growing in is broken into microscopic water droplets. This can easily happen at a shower head, sink faucet or at the end of a hose.

Once the contaminated water becomes an aerosol, it can be easily breathed into human lungs where it will begin to attack healthy cells and multiply.

The four biggest areas of legionella transmission are cooling towers, potable water systems used for showering, hot tubs and decorative fountains; however, there have been outbreaks that have been liked to other infestations, like contaminated topsoil that was disturbed and made airborne. In almost every account of a legionellosis outbreak, the bacterium is made airborne and the human host breathes it in. After approximately 10 days of the bacteria multiplying in the perfect environment of a person’s lungs, symptoms start to manifest; these include a horrible cough and high fever. The human body tries to fight the infection by producing phlegm, and the lungs suffer symptoms that closely resemble severe pneumonia.

Diagnosing Legionnaire’s Disease

If someone shows signs of Pontiac Fever or severe pneumonia, a hospital may perform a test to determine if the patient has Legionnaire’s Disease. There are two primary methods of testing a patient: a urine test for the Legionella antigen or Legionella culture of a respiratory sample.

The first is a urine test that easy to administer and produces a result quickly. The benefit is that the patient can be quickly diagnosed and, therefore, treated with certainty; however, this method only produces a YES/NO result. “Yes, you have it” or “No, you don’t.”

The more involved laboratory culture testing of lung tissue or phlegm is considered the “gold standard” for diagnosing an infection caused by Legionella bacteria. Since a culture test can identify multiple Legionella species, it can also be used to help identify the source of the outbreak.

Is Legionnaires’ Disease Curable?

Legionnaires’ disease is dangerous, but treatable.  It is commonly treated successfully with antibiotics. Most people who get sick need care in a hospital but make a full recovery. However, about 1 out of 10 people who get Legionnaires’ disease will die from the infection. The people who are most at risk are ones that have pre-existing underlying issues. For example, legionellosis is most dangerous to someone with an already compromise immune system, or a smoker, or the very young or very old.

Legionella & Cooling Tower Laws

For years there have been no established laws in the United States that specifically govern the operation of cooling towers or the prevention of Legionella, as there are in Europe and Great Britain. In fact, in England, the Health and Safety Executive (HSE) gives specific guidance to the public on how to comply with the Health and Safety at Work etc Act 1974 (HSWA) which extends to risks from legionella bacteria, which may arise from work activities.

Only recently have New York City and the State of New York passed legislation designed to protect the public from dangers associated with Legionella in cooling towers. The New York Cooling Tower laws are comprehensive and call for assessment, monitoring and control, and responsibility when it comes to preventing Legionella and protecting the public.

The New York cooling tower laws were passed in direct response to the worst Legionnaires’ disease outbreak in New York City’s history, during the summer of 2015. Even though the laws were passed in New York, industry and legal experts agree that the implications of the NY laws and ASHRAE Standard 188 will reach building owners that do not properly care for their water systems in other states.

Legionella Risk Assessment

A risk assessment is an integral part of any Legionella Risk Management Program. Building owners are responsible for determining whether or not people that interact with their properties may be at risk for Legionella infection.  Any water system that has the right environmental conditions could potentially be a source for legionella bacteria growth. There is a reasonably conceivable Legionella risk in your water system if:

  • the water temperature in all or some part of the system may be between 68 to 114°F;
  • there is the potential for dead legs, or areas of low or no flow, in your system
  • there are deposits or debris in the system that can support bacterial growth, such as rust, sludge, scale and organic matter;
  • it is possible for water droplets to be produced and, if so, if they can be dispersed;
  • it is possible for any of your employees, contractors, tenants, or visitors to be exposed to any contaminated water droplets.

Cooling towers, potable water systems used for showering, hot tubs and decorative fountains are very common sources of Legionella exposure. If you have any of these types of systems on your property, you should consider seeking out the counsel of a Legionella Environmental Consultant or Water Treatment Company that can conduct a Legionella Risk Assessment.

Identifying Sources of Legionella

Legionella testing is the only way to determine if a water source is contaminated with the bacteria. Even though a heterotrophic plate test (dipslide test) will show if there is biological activity in a body of water, it does not provide a clear indicator of legionella contamination. While there is more than one method for testing for legionella, the following are the most popular:

  1. Cultured Samples – Water samples are cultured on a buffered charcoal yeast extract (BCYE) culture growth medium. Preliminary culture results typically require three to five days for confirmation from the time of submission. Confirmation of culture results may take additional time because some strains take 10 to 14 days to form visible colonies. Cultured samples may be analyzed to identify specific serogroups. There is strong evidence of a causal relationship when the same serogroup and subtype of an organism is isolated from a patient and a water source.
  1. Direct Fluorescence Antibody (DFA) – The number of organisms in a water sample can also be determined via direct fluorescence antibody (DFA) conjugate tests that stain the organism with a fluorescent dye. While this testing method can produce a result in as little as one or two days, a potential drawback to the DFA test is that it is unable to distinguish between live and dead bacteria and may have some cross-reactivity with other bacteria; and so the potential exists for both false-positive and false-negative results.
  1. DNA Amplification – A relatively new method for rapid, specific detection of Legionella bacteria in water utilizes a polymerase chain reaction (PCR) process to amplify and then detect portions of DNA that is unique to Legionella. DNA Amplification can produce results in one day.

Legionella bacteria live in a wide variety of freshwater habitats and they can be difficult to isolate when testing. Culture and enumeration of Legionella from environmental sources involves several steps including concentration of the bacteria, resuspension, selective pre-treatments, and the use of complex media. The Centers for Disease Control and Prevention created the ELITE Program as a way for laboratories to test their Legionella isolation techniques against standardized samples. ELITE is an acronym for “Environmental Legionella Isolation Techniques Evaluation.” ELITE Certified Labs are sent a panel of test samples twice per year.  Labs that correctly identify Legionella from the test samples in two consecutive panels receive a certificate of proficiency and are listed among the CDCs ELITE Members.

Cultured samples analyzed by a CDC Elite lab is currently the “method of choice” in the United States.

These are the common sites where people are exposed to legionella bacteria in aerosolized water droplets.Legionella Prevention

Legionella bacteria are considered to be ubiquitous, meaning that they are found just about everywhere. They naturally appear in fresh water and soil; however, normal environmental conditions keep Legionella populations at bay in most water environments. The concept of Legionella being omnipresent is so prevalent that there is a saying in the water treatment industry: “If you search for legionella, you are certainly going to find it.” The real question is: How do we keep the most common areas of Legionella transmission operating in a safe manner for humans? The answer is: by putting a proactive system in place that ensures proper preventative measures and maintenance. Water treatment companies are a first line of defense in the prevention of legionella.

In June or 2015, the American Society of Heating, Refrigerating and Air-Conditioning Engineers published ANSI/ASHRAE Standard 188-2015, Legionellosis: Risk Management for Building Water Systems. Standard 188 and the Cooling Tower Institute’s guideline “Legionellosis – Guideline: Best Practices for Control of Legionella” are currently the most widely cited works in the United States on the subject of preventing legionella in cooling towers. Portions of ASHRAE Standard 188 were even written into New York City’s cooling tower laws.

These guidelines, as well as many others, are based in the principle that the key to preventing legionellosis is making sure that the water systems in buildings are properly and proactively maintained and monitored in order to reduce the risk of growing and spreading Legionella.

Legionella Remediation & Disinfection

Any water system that is contaminated with Legionella is a serious matter that needs to be dealt with swiftly and effectively. Not all water system can be or should be disinfected the same way. Limitations imposed by location and engineering are factors that need to be evaluated on a case-by-case basis.  For instance, large potable water distribution systems, like the ones found in hospitals, would be disinfected using different methods than those used to disinfect a large cooling tower.

There are many options available to disinfect potable water distribution systems, including hyperchlorination, thermal eradication, chlorine dioxide generation, copper/silver ionization, ultraviolet light, and instantaneous heating system. No one method is a panacea for all remediation situations, and each method has clear advantages and disadvantages depending on the situation. This article gives some great examples of the advantages and disadvantages of some Legionella disinfection methods.

In cooling towers, the method for disinfection can and should be more aggressive because humans are not consuming the water and because the possibility of infecting groups of people on a larger scale in a shorter amount of time. Hyperchlorination combined with physical cleaning is the most relied upon method. This type of option is also acceptable in decorative fountains and hot tubs.

Regardless of the method employed, a successful Legionella remediation and prevention program requires evaluation, analysis, cooperation, communication and a dedicated team. Plan creation is unique to each installation. Options are usually dependent on budget and maintenance options available, and must be evaluated on a system-by-system basis. Success will always be dependent on a meticulous monitoring program, a committed staff and proficient vendors.