How do you test for legionella?

Legionella risk and pat blog's

Legionella bacteria, also known as legionella pneumophila, are usually harmless. However, some types can cause serious human disease infections including Legionnaires’ disease. These bacteria live in water systems such as cooling towers, hot tubs, whirlpools, fountains, drinking water supplies, and air conditioning units. While they typically thrive in warm temperatures and low levels of oxygen, they can also materialise in cold water systems.

The testing of individuals is recommended for anyone who shows symptoms of pneumonia and has been exposed to contaminated water sources. Bear in mind, though, that if you test positive for Legionella, it does not necessarily mean you have Legionnaires’ disease. You might just have Pontiac fever, or another related illness. In this article, we answer the most commonly asked questions about Legionella tests.

Why do I need to take a legionella test?

Exposure to legionella bacteria can cause the development of a number of pneumonia-like symptoms such as

  • Fever over 101°F
  • Headache
  • Muscle aches
  • Confusion
  • Nausea and/or vomiting
  • Gastrointestinal symptoms 
  • Flu-like symptoms

Taking a legionella test, if you have any of these symptoms, can confirm whether you have Legionnaires’ disease or not, and enable you to begin treatment in a timely manner, thereby avoiding serious complications such as lung disease and weakened immune system.

Get your water tested to minimise the risk of legionella exposure

Can I test for legionella myself?

There are different types of tests and diagnostic methods used to detect Legionella bacteria. These include culture, immunoassay, antigen detection, PCR, and nucleic acid amplification test. Each has its advantages and disadvantages. However, there are some commonalities among the most commonly-used tests.  While some tests can be self-administered, the vast majority require the help of a third party medical professional. 

Below are some of the most common legionella diagnostic tests: 

Urinary Antigen Testing

The most commonly used laboratory test to diagnose Legionnaires’ disease is called the Urinary Antigen Test (UAT). This test looks for a specific protein produced by the bacteria. A positive result indicates the presence of legionella pneumophila and points to the presence of Legionnaires’ disease or Pontiac fever. In some cases, it can take up to three weeks for the test to turn up positive. 

Blood test

Blood tests for Legionella pneumophila antibodies are no longer routine, but may be available from certain reference laboratories. These detect antibodies and the body’s immunological response to a legionella attack in the blood. This test is not useful for immediate medical decisions but can be ordered to confirm the presence of a recent infection. In most cases, two blood samples, taken several weeks apart, are required to obtain reliable results.

Usually, two negative antibody tests indicate that the person does not have a current legionella infection. However, a single positive result can occur due to cross reactivity with another bacterium. Cross reaction takes place when the same antigenic determinant is shared among different species. For example, antibodies produced during a previous infection with Streptococcus pneumoniae might cross react with antigens found in Legionella species. If you have had a recent bacterial respiratory tract infection, you could yield a false positive result.

Legionella Culture

This approach involves the examination of culture samples to see if the patient has been infected by Legionella pneumophila. Specialised media is needed to grow Legionella, which is why it doesn’t compete with other bacteria. Cultures take 48 to 72 hours to yield results. They typically test negative after seven days.

What happens during a legionella test?

The process of collecting a urine sample is extremely simple. You will be provided with a collection container within which you will need to urinate. In order to receive an accurate diagnosis, you should ensure that your hands are clean and that you are able to properly collect your urine sample in the container. 

Following this, all you need to do is hand the sample to the physician and wait. Legionella infections usually occur 2–10 days after exposure to contaminated water. A person infected with Legionnaires’ disease must wait 10 days after symptoms begin before testing for the disease.

Can you get legionella from a shower?

Will I need to do anything to prepare for the test?

In most cases, you will not need to do anything in order to prepare for a legionella test. A urine test needs no preparation at all, but a blood test might require some minor preparation. For example, you might need to refrain from eating or drinking, and you might need to mentally prepare yourself if you are afraid of needles. The best thing to do is to talk to your healthcare provider to find out what you need to do before your test. 

Are there any risks related with legionella tests?

There are no risks to providing either a urine or sputum sample. However, you should be aware that some people are allergic to latex gloves. If you do develop a rash, stop the procedure immediately. A nurse will give you another pair of gloves in order to enable you to continue.

With regard to blood tests, you may experience slight pain or develop a bruise on the spot where the needle was put in, but most of the symptoms go away within minutes. Some patients experience nausea or vomiting, but this usually goes away within hours.

How long does it take to test for legionella?

If you have a legionella culture taken, which is widely considered the gold standard of legionella testing, then you can expect your results to be processed extremely quickly. If you test positive for legionella, you will get your results in 48 to 72 hours, whereas if your test is negative, you may have to wait up to a full week in order to confirm the result. 

What do legionella test results mean?

A simple blood test can tell you whether you are infected with Legionnaires’ disease. A negative result doesn’t necessarily mean that you don’t have Legionnaires’ disease; it could simply mean there wasn’t enough legionella in your sample. If you test positive, your doctor will immediately begin a course of treatment. This will usually be an antibiotic treatment, which will begin to fight off the disease. 

Legionella testing services

Legionnaires’ disease testing goes beyond merely having yourself examined in the event of symptoms. It also involves checking the water supply from which it originated. It is imperative that you identify which water source you contracted the disease from, in order to make sure no one else uses it and the problem is fixed immediately. 

Outbreaks of legionnaires must be taken extremely seriously, which is why any possible water source that might carry the disease needs to be checked thoroughly. The process of testing is easy and can be comprehensively carried out by water specialists. Whether you need to check commercial or domestic water sources, we are dedicated to detecting the source of the problem. 

Control of legionella bacteria is our number one priority. After all, if one person contracts the disease, an entire community might be at risk. Therefore, if you have recently tested positive for legionella pneumophila and need to minimise any foreseeable risk, contact us and we will discover the source of the problem for you and help you fix it as soon as possible. 

Identify legionella contamination with comprehensive risk assessments 

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