Bacterial and Parasitic Infections

2022 HIGHLIGHTS

Buruli ulcer project sets the scene for future targeted public health responses 

In 2022, Victoria saw an increase in reported cases of Buruli ulcer, a disease now endemic in parts of the state. ‘Beating Buruli in Victoria’ is a world-first collaborative research project led by the Stinear group that made significant strides in understanding disease transmission and prevention. In particular, they have shown that there is growing evidence that mosquitoes and possums have a role in transmitting the bacterial infection in Victoria.

Their research on mosquitoes found that Aedes notoscriptus, a common mosquito species, consistently tested positive for Mycobacterium ulcerans, the bacteria responsible for Buruli ulcer, and travelled longer distances than previously thought. This species-specific insight is important for the development of effective mosquito control strategies to prevent transmission. Among the methods tested, insecticide spraying and mosquito traps were the most successful in reducing mosquito populations. Following community input, spraying was halted in favour of conducting a more extensive study of the trap-based approach. A possum surveillance program identified infection risk factors based on location. Researchers used DNA testing to detect M. ulcerans in possum excrement. Combining these findings with geo-localisation data, they revealed locations where possums were excreting the bacteria. Together with environmental risk factors for infection, such as the presence of ringtail possums, overhead powerlines and native vegetation, this method allowed for the precise identification of hotspots with a higher risk of Buruli ulcer. This has the potential to improve public health interventions with the control of mosquito populations in specific areas where possums have been found to shed M. ulcerans to protect the local community from the disease.

Work begins on developing a new therapeutic to fight pneumonia in the community

The McDevitt group is investigating new ways to treat infections caused by drug-resistant bacterial pathogens responsible for community-acquired bacterial pneumonia (CABP). CABP is a highly prevalent infection in Australia, with Aboriginal and Torres Strait Islander people at greater risk of longer hospital stays and death from the disease. Treatment outcomes are worsening globally as more of the pneumonia-causing bacteria are increasing resistance to antibiotic treatments. The team’s new project aims to use a molecule, called PBT2, to restore the ability of frontline antibiotics to effectively treat CABP.

Precise genome sequencing sheds light on how tuberculosis spreads in Victoria 

Although it is well known tuberculosis (TB) spreads within households, a study published by Doherty Institute scientists from the Victorian Infectious Disease Reference Laboratory (VIDRL) and Microbiological Diagnostic Unit Public Health Laboratory (MDU PHL) used precise genomic sequencing to better understand how TB is transmitted within Victoria. Their work revealed that the infection spreads among young adults in social settings, but also among people with no identified connections. The team hopes these results will inform future TB management and contact tracing with the goal of eventually reducing the number of cases globally.

Research paints the most comprehensive picture of the true burden of a severe bacterial infection in Victoria 

In an Australian first, researchers led by the Royal Melbourne Hospital’s Dr Katherine Gibney, Medical Epidemiologist at the Doherty Institute, have linked and analysed a large amount of data from multiple sources across Victoria to identify epidemiological trends and outbreaks of Invasive Group A Streptococcus disease (iGAS) between 2007 and 2017. The results showed that iGAS cases increased considerably from 158 in 2007 to 327 cases in 2017, and the fatality rate was much higher in people aged 75 years or older.

As a disease that causes severe and life-threatening infections, iGAS is now notifiable in Australia, a decision supported by this research. Researchers anticipate that this study will improve our understanding of the disease, accelerate identification of changes in epidemiology and enable targeted public health responses. This new approach of linking multiple datasets to investigate the true burden of iGAS could be used to aid in targeting treatments and future vaccines for people at highest risk of the disease.

Emerging field of research transforms mapping of golden staph infections

In a collaborative research study led by the Howden and Stinear groups, scientists used a combination of genomic analysis and computational science, a field known as ‘statistical genomics’, to detect real-time genetic changes in antimicrobial-resistant Staphylococcus aureus, also known as golden staph. Golden staph can cause life-threatening infections that are increasingly resistant to the strongest antibiotics. The statistical genomics approach found new genes not previously known to be linked to resisting antibiotic treatments. This new methodology provides real-time insights into the genetics of Golden staph and has the potential to support development of new treatment approaches.

Insights into the current syphilis epidemic in Australia

Published in The Lancet Microbe, a genomic and epidemiological study revealed the complex landscape of the ongoing syphilis epidemic in Australia. Researchers, led by University of Melbourne Honorary Professor Deborah Williamson at the Doherty Institute, examined the genomes of more than 450 clinical samples containing Treponema pallidum, the bacterium that causes syphilis, to investigate the emergence and evolution of this sexually transmitted infection in Australia and uncover what is driving its increase over the past decade. They found that, rather than a single outbreak, the epidemic stems from a multitude of T. pallidum strains, categorised into twelve subgroups, that emerged within the last 30 years, are closely linked to global lineages and are present across diverse sexual networks. Worryingly, the whole-genome sequencing analysis showed that 87 per cent of the T. pallidum strains have developed resistance to common antibiotics. This concerning finding complicates treatment strategies, as it limits the options to effectively manage and treat cases.

Researchers suggest that these findings underscore the importance of a nuanced and tailored approach that targets the overlapping sub-epidemics of syphilis, rather than a uniform, one-size-fits-all public health strategy.

Iron deficiency linked to lower malaria risk during pregnancy

In a clinical trial led by University of Melbourne Professor Stephen Rogerson, Head of the Malaria Laboratory at the Doherty Institute, in Papua New Guinea, researchers found that iron deficiency, common among pregnant women, was associated with a reduced risk of malaria infection, especially in first pregnancies. However, their findings show that, while higher iron levels were linked to increased malaria risk at delivery for first pregnancies, it was not the case for women who had had previous pregnancies.

More research is needed to fully unravel the exact mechanisms behind maternal iron levels and susceptibility to malaria. This has the potential to improve prevention and treatment strategies with tailored solutions for pregnant women in malaria-endemic regions.