Potting mix and compost are a breeding ground for fungi, but how likely are you to get sick?

Gardening is a healthy and fulfilling hobby for many Australians. But like many activities in our day-to-day lives, there is some risk involved — particularly when it comes to using potting mix and compost.

Potting mix and compost can contain legionella bacteria which cause Legionnaire’s disease, a potentially deadly form of pneumonia.

These products are also breeding grounds for fungi.

Queensland man Paul Minuzzo had his top jaw and teeth removed after contracting a life-threatening fungal infection known as mucormycosis.

Mr Minuzzo doesn’t know where the infection came from, but he was told by a specialist that it may have been caused by spores in potting mix.

While mucormycosis infections can be life-threatening and hard to treat, they’re also very rare. Nevertheless, there may be some precautions that are worth taking to reduce your risk.

Who is at risk of fungal infections while gardening?

Fungal infections such as mucormycosis are predominantly found in people with compromised immune systems such as those who have undergone transplants or are being treated for cancer with chemotherapy, explains Professor Monica Slavin.

She’s the director of the infectious diseases department at the Peter MacCallum Cancer Centre, and the director of the National Centre for Infections in Cancer at the University of Melbourne.

“These fungal spores are all around us. We inhale them every day and our immune system in our lungs just eliminates them,” she says.

“But if you have a compromised immune system, [the spores] can lead to a problem.”

People with diabetes have a slightly increased risk of infection because these fungi prefer hosts with high blood sugar.

In most cases, infections are caused by breathing in fungal spores. However, you can also become infected through a gardening injury.

“It’s not an uncommon thing in gardening; sometimes people can injure themselves and have some sort of puncture that introduces soil into their body,” Professor Slavin says.

“That can set up a fungal infection.”

Will wearing a mask help protect you from fungal infections?

Professor Slavin says for most people, “Gloves, good shoes and covering up your skin should be enough [protection], really. Unless you’re dealing with potting mix or compost, [in which case] I think it’s not unreasonable to wear a mask.”

While fungal infections are rare, taking precautions while gardening can help reduce your risk, Professor Slavin says.(Doherty Institute)

She says it is “very unlikely” that an otherwise healthy person would contract mucormycosis from gardening.

“When a healthy person contracts it, it’s usually after an accident where they’ve perforated their skin or they’ve breathed in a huge amount of [spores from] soil,” she says.

“In day-to-day gardening activities, you’re probably not at huge risk.”

Professor Slavin explains it’s important for immunocompromised people to take extra precautions when dealing with potting mix, compost, soil or other gardening products containing decaying organic matter.

In addition to protective footwear and clothing such as gloves, she recommends wearing an effective face mask such as an N95 to filter out spores.

How likely are you to get sick from fungal infections while gardening?

Professor Slavin says we don’t have great data about the number of mucormycosis infections, and we don’t know how many are caused by exposure to spores from potting mix and compost.

“We have from several years ago a study where we looked at it over about five years and from 15 different hospitals in Australia,” she says.

“A big teaching hospital might see five cases [of mucormycosis] per year — it’s not very common.

“That one is probably our number two fungus; number one would be aspergillus. With aspergillus, you might see four or five times as many cases as mucormycosis.”

Fungal infections are harder to treat than bacterial infections, and can be harder to diagnose, she adds. Often, mucormycosis infections can be life-threatening and need urgent treatment.

“Because they invade into blood vessels and the tissues, they can cause blockages and tissue can die,” she says.

“They actually then like to grow on that dying tissue. They are very smart in terms of how they invade the human body and cause tissue death and then can live on that dying tissue.

“There’s not one universal treatment and the treatment is prolonged. It often relies on not only antifungal treatment but surgery to remove the dead areas of tissue and reduce the burden of the fungus in the tissue.

“We often treat people for weeks to months, sometimes even longer.”