30 years of studying and treating a deadly bacterium

Menzies School of Health Research leads global collaborations in addressing the potentially fatal tropical disease melioidosis.

Thirty years ago, over 30 per cent of melioidosis patients in Royal Darwin Hospital died from the disease. It was the most common cause of fatal community-acquired bacteremic pneumonia in the Top End. Today mortality is less than five per cent.

Clearly, something happened along the way.

Stormy beginnings

Severe Tropical Cyclone Kathy formed in Australia’s Gulf of Carpentaria on 16 March 1984. It quickly grew into a Category 5 storm: a ‘monster’ menacing the Northern Territory township of Borroloola. Three fishing vessels were hammered by cyclonic winds for eight hours, and one of the trawlers sank resulting in the loss of life of one crew member.

Tropical Cyclone Kathy crossed the coast north of Borroloola on 22 March 1984 as a Category 4 storm; large numbers of dugongs and green turtles were carried over the flat coastal land, and a dugong was found 8 km inland.

That same year in Darwin, Menzies School of Health Research was officially opened in June 1984.

Getting started

The following year in January 1985, Menzies began its work in research, specifically into life threatening tropical diseases, with a major focus on improving Aboriginal and Torres Strait Islander health and wellbeing.

Melioidosis is a tropical infectious disease caused by the bacterium Burkholderia pseudomallei and is found in soil and surface water in areas where melioidosis is endemic: commonly Southeast Asia and Northern Australia, but also in other parts of Asia, including China, India, and Sri Lanka.

Melioidosis was first described in Australia in an outbreak in sheep in 1949 in north Queensland, and the first human case of melioidosis was from Townsville in 1950 and the first human case in the NT was in 1960.

In the Northern Territory, melioidosis is a common cause of serious pneumonia and blood poisoning. The bacteria live below the soil’s surface during the dry season, but after heavy rainfall can move to and proliferate in surface water and mud; and from there, can become airborne during severe weather events.

Taking action

Due to the high number of melioidosis cases and mortality in the Northern Territory, the Darwin Prospective Melioidosis Study began in October 1989, and continues today.

The study is spearheaded by Professor Bart Currie from Menzies School of Health Research and Royal Darwin Hospital, who said that the study’s primary aim has been to decrease mortality from melioidosis in the Northern Territory through ‘public’ and ‘health staff’ recognition of melioidosis; better and quicker diagnosis; use of newer, better antibiotics; and state-of-the-art hospital care for critically ill patients.

“With early diagnosis, best antibiotics and ICU treatment, healthy people should not die from melioidosis,” Prof Currie said.

Building teams  

Senior Researcher Mark Mayo came to Menzies in 1992 as a laboratory trainee under the mentorship of Menzies scientists Professor Amanda Leach and the late Professor Dave Kemp, where it wasn’t long before Mark’s talents were realised.

After completing University study, Mark optimised pulsed field gel electrophoresis typing of the melioidosis bacterium to study clusters of melioidosis cases and he has subsequently spent the past twenty-one years as the Program Manager for the Darwin melioidosis team, working alongside Professor Currie.

Senior Researcher Mark Mayo and Professor Bart Currie

“We work across Australia’s tropical north and also throughout Southeast Asia in collaboration with our partners in Thailand, Singapore, Malaysia, Cambodia and beyond, and we can see that our work is having a real impact, and lives are being saved,” Mr Mayo said.

“It’s great to be working with scientists, physicians and researchers that are at the top of their game.”

Collaboration

While the melioidosis program at Menzies has driven the research questions and the coordination and publication of new findings in diagnostics and therapy, it is the broad collaboration with hospital doctors and nurses and the NT CDC public health team that has translated the research into best practice that has driven down the mortality. In turn, two decades of close collaborations with colleagues around the world through the International Melioidosis Network (https://www.melioidosis.info/) underpins the better understanding of the global epidemiology and pathogenesis of melioidosis.     

The 2020 revised Darwin Melioidosis Treatment Guideline is used internationally and has recently been adopted by the US CDC in its recommendations for therapy of melioidosis.

“This is what the Royal Darwin Hospital microbiology laboratory, Infectious Diseases Department and ICU have learnt, and the 2020 Darwin melioidosis treatment guideline is now used internationally.”

Professor Bart Currie

A fascinating though fatal evolution

It is now known that bacterium Burkholderia pseudomallei originally came from central and northern Australia, with subsequent spread to Southeast Asia during the last ice age; it then spread to Africa, and then more recently, to the Americas.

In the United States between March and July 2021, there were four confirmed cases of melioidosis resulting in two deaths, a mortality of 50 per cent.

In October, the US CDC said the source of the bacteria was traced to a room spray sold by Walmart, which has since been recalled. The spray was manufactured in India, with water contaminated with the melioidosis bacterium likely to be the source of infection in the spray.

Spreading the word

The US based magazine The Scientist contacted Prof Currie in August 2021 following the fatal outbreak.

“What’s happened in the last 20 to 30 years is that the global distribution of the organism Burkholderia pseudomallei has been recognized to be much more than was originally thought.”

“Here in Australia, where melioidosis is endemic for us, we’ve recognized two other Burkholderia pseudomallei strains which are different from our usual Australian strains and which we think have been imported from Asia. So even in our endemic area where we understand melioidosis and study it, we are struggling to figure out how it’s actually getting back into Australia from outside the country,” Prof Currie said.  

Looking ahead

Modelling done by Menzies suggests that increasing rates of diabetes, climate change and landscape disturbance from development of northern Australia will each contribute to growing numbers of melioidosis cases for the foreseeable future.

“Analysis of our 30 years of cases and links to weather also provides consistent evidence that global warming is likely to increase the risk of melioidosis in the future and expand the boundaries southward,” Prof Currie said. “With colleagues in Australia and overseas, we also have found that there are unexpected instances of melioidosis outside the tropics and more work is needed to understand these occurrences.”