Around 2 to 3 people are hospitalised with Legionella longbeachae infection every year in Darwin. It causes fever, cough and breathlessness. It’s a bacterial infection well known to come from soil and potting mix. The standard antibiotic treatment course given in hospital for pneumonia covers this bacteria and cures it effectively. But occasionally, especially if there is a delay, the infection can become very severe.

There are many infections in Northern Territory Top End soils that can get into the lungs, and Legionella longbeachae is one of them. At this time of year, the more common and important soil infection is melioidosis, which people in the Top End are very familiar with. There have already been 5 new cases of melioidosis in Darwin since the start of October. The strategies to protect from melioidosis are the same as the ones that can protect against Legionella longbeachae - avoiding getting stuck outside in a storm, using a mask and gloves when you’re handling soil or potting mix, especially if you already have a lung conditions or a low immune system, and avoiding drinking too much alcohol which stops you effectively fighting infection.

The antibiotics needed for these infections are different, but if you have pneumonia, diagnostic tests can help work out which infection is present, so the right treatment can be given.

Legionella causes a bacterial infection which usually affects the lungs (pneumonia) up to 10 days after being exposed to it. Not everyone exposed to Legionella will get sick. Those particularly susceptible to getting sick with Legionella include smokers, the elderly, those with weakened immune systems, and those with chronic lung disease.

Legionella outbreaks are typically associated with contaminated water cooling towers. But it is a bacterium that is also found in the soil. One species in particular, Legionella longbeachae, can be inhaled from potting mix. That is why it is recommended that people using potting mix should wear a mask and wash their hands afterwards.

Most people using potting mix won't get Legionella pneumonia, but antibiotic treatment is available for those who do. The infection is named "Legionella" because it was first isolated in relation to an outbreak at the American Legion's Convention in Philadelphia.

Legionella is the bacteria that causes Legionnaire’s disease, which is a severe pneumonia-like infection. It can also cause Pontiac Fever, which is like a bad flu. You can also get an asymptomatic increase in Legionella antibodies. This means that many people are exposed to the bacteria, have an immune response, but don’t have any symptoms or get sick. 

Those at greatest risk of Legionnaire’s disease are the elderly, smokers and the immunocompromised. 

In Australia, the two species of Legionella that most commonly cause Legionnaire’s disease are Legionella pneumophila and Legionella longbeachae.

L. pneumophila is found in engineered water systems such as cooling towers, spa baths, swimming pools and showers, whereas L. longbeachae is found in potting mix and soil. 

Legionnaires disease is not transmitted person to person, but through inhalation or aspiration of the Legionella bacteria. This is why it is important to wear a mask, wet down soil and wear gloves/wash hands when handling potting mix.

Legionella are environmental bacteria that can cause life threatening lung infections in susceptible people following exposure to contaminated water or soil. 

The infection is not spread from person to person and most people can fight off the infection quickly. 

While most Legionella outbreaks are spread by water aerosols, potting mix is an ongoing area of public health concern as soil can contain Legionella longbeachae, which is capable of causing fatal infections in people. 

Since Legionella is impossible to eradicate from the environment, people should take measures to protect themselves if undertaking a known risk activity such as gardening with potting mix. 

This includes wearing a face mask, protective eye wear and gloves and allowing particles and dust to settle after opening the potting mix. Legionella causes flu-like symptoms and prompt diagnosis has a better prognosis as antibiotics are generally effective against the bacteria if given early.  

If feeling unwell after handling potting mix, people should seek medical attention at the first sign of symptoms. 

However, it should be noted that standard diagnostic tests are not designed to detect Legionella longbeachae, so it’s important to mention a risk activity like gardening with potting mix to medical practitioners for more specialised testing.

Legionnaires’ disease is caused by Legionella bacteria with illness most commonly associated with Legionella pneumophila serogroup 1. Multiple serogroups of L. pneumophila are known to cause disease as well as L. longbeachae, L. micdadei and L. bozemanii. Legionnaires' Disease, is an acute severe pneumonia, with patients often presenting with flu-like symptoms.

Legionella are widely distributed in the environment and has been found in lakes, rivers, creeks and other bodies of water as well as soils. Man-made water systems such as cooling towers can provide conditions in which the bacteria can multiply to large numbers therefore legionellosis is more commonly associated with the inhalation of the bacterium from contaminated water but infection from contaminated soil can occur. Earlier studies have shown that apart from L. pneumophila, L. longbeachae has been associated with potting mixes (Steele, et al., 1990 and Steele, et al., 1990). It is recommended that gloves and a mask be worn when handling potting mixes to prevent inhalation from potentially contaminated soils."