Australian discovery may help counter Legionnaires' disease outbreaks

Groundbreaking research by Dr Michael Taylor has led to a better understanding of the bacterium

Contaminated water samples were collected and a laser microscope used to produce images of the bacteria. Credit: Flinders University

Flinders University microbiologist Dr Michael Taylor has taken three-dimensional images of the bacteria that offer vital insights into the behaviour of the potentially-fatal Legionella bug, providing new data that could influence future cleaning practices of water systems.

Dr Taylor said he produced the images by growing a range of bacteria, including Legionella, on a rugged microscopic “landscape” then colour-coded their individual DNAs with a fluorescent chemical in order to tell them apart.

“We ended up taking a series of photos which sliced all the way through the slimy film where the organisms were growing,” Dr Taylor, whose research formed part of his just-completed PhD, said.

“Organisms like to live in different areas of their environment so when we stacked the images we could see a 3D view of where the Legionella tended to grow, and importantly, if it could survive outside of another organism,” he said.

“As far as we know, no-one else in the world has actually taken a section of film with all different organisms on it and looked for Legionella in this way.”

Discovered in 1976, Legionella is a naturally-occurring bacterium that thrives in man-made water systems, including showers, spas, cooling towers and soil. Under the right conditions, the bug can grow to uncontrollable levels causing Legionnaires’ disease – a serious and sometimes fatal form of pneumonia contracted by breathing in the bacteria.

About 50-100 cases of Legionnaires’ diseases are reported in Australia every year, although Dr Taylor said a poorly-maintained cooling tower had the potential to cause a large-scale outbreak that could affect “hundreds of people”.

He said the novel research offered important new evidence to suggest the aquatic organism could exist on its own by gaining nutrients from multiple sources, contradicting the popular scientific belief that Legionella is only capable of surviving by feeding off a host.

The information, he said, could change the way human-made water systems were cleaned.

“To disinfect a cooling tower you usually add chemicals to the entire system but if you know where and how Legionella grows you could target the specific area, rather than the host location,” Dr Taylor said.

“If you had a pipe system, for example, where one end was hot and the other was cold, generally the Legionella would grow in the hot area and the host would live in the cold part.

“But if you thought the bacteria only survived in the host you might only clean the cold part, thinking the rest of the system was fine when in fact it could be harbouring Legionella.

“What’s great about these images is that it clearly illustrates how the bacterium survives, what it interacts with and under what circumstances, meaning we can better understand why it turns up in some places and not in others.”