Stinear Laboratory
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Page ContentsInclude: Research interests | Mycobacterium ulcerans | Staphylococcus aureus | Enterococcus faecium | Laboratory staff | Collaborators | Useful Links | Some recent publications from the group | Research Funding |
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Research interests
The Stinear Laboratory uses genomics and molecular biology to understand how certain groups of bacteria evolve and cause disease in humans. We then try and translate that knowledge into improving human health. For example, we have used our findings to guide the use of antibiotics for improved treatment of infections and to develop better diagnostic methods that can more rapidly and accurately detect infections. We focus our research efforts on the bacterial pathogens Mycobacterium ulcerans, M. marinum, M. tuberculosis, Staphylococcus aureus and Enterococcus faecium. Our laboratory works in close partnership with the Infectious Diseases and Microbiology Departments at Austin Health and the World Health Organization Collaborating Centre for Mycobacterium ulcerans at the Victorian Infectious Diseases Reference Laboratory.
Mycobacterium ulcerans
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Mycobacterium ulcerans causes Buruli ulcer, a serious skin disease characterized by chronic ulceration of subcutaneous fat that can leave victims with debilitating, life-long deformity and disability (Fig. 1). M. ulcerans is related to M. tuberculosis and M. leprae, the causative agents of tuberculosis and leprosy respectively. An 8-week course of the antibiotics rifampicin and streptomycin is the World Health Organisation recommended treatment, sometimes supported by surgery and skin grafting if the damaged area is extensive. There is no vaccine against Buruli ulcer. The disease is found throughout the world, including Australia where recent outbreaks in Victoria have coincided with an ongoing epidemic across West and Central Africa. In rural Central and West Africa the prevalence of Buruli ulcer now exceeds leprosy and, in some instances, tuberculosis. In 1998 the World Health Organization launched the Global Buruli Ulcer Initiative with the principal aim of trying to control the spread of this debilitating disease. | |
| Figure 1: A typical village in West Africa where Buruli ulcer occurs. |
| M. ulcerans produces an unusual lipid toxin called mycolactone (Fig. 2). This molecule is thought to be the major determinant of virulence because injection of purified mycolactone into the skin of guinea pigs provokes the appearance of ulcers. Mycolactone has been shown to have cytotoxic and immunosuppressive properties but the precise role it plays in pathogenesis is still unclear. It is also possible that M. ulcerans may elaborate other factors that play a role in ulcer formation. Some years ago in collaboration with the Institut Pasteur we determined the genome sequence of M. ulcerans. A major finding from the genome project was the discovery of a virulence plasmid and three polyketide synthase (PKS) genes on this plasmid required for mycolactone biosynthesis. The 12-membered core of mycolactone is produced by two giant type I modular PKS, whereas its side chain is synthesized by a third PKS. |  |
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The availability of the complete genome sequence provides an important resource for international research efforts aimed at controlling the spread of Buruli ulcer. In this respect the research within our group is focused on:
- Using genome data to identify and characterize M. ulcerans specific antigens for use in the development of a rapid diagnostic tests and vaccine studies.
- Using genome data to identify potential determinants of virulence other than mycolactone.
- Developing systems for heterologous expression of mycolactone so that a reliable source of mycolactone
and derivatives is available for:
- determining the role of mycolactone in the bacterium
- establishing the relationship between mycolactone structure and function in the host
Staphylococcus aureus
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Staphylococcus aureus still remains a dangerous human pathogen,
with the ability to cause a broad range of diseases, such as bacteremia, endocarditis, sepsis and
toxic shock syndrome. Over the last 20 years there has been an increasing incidence of both
hospital-acquired and community–acquired S. aureus infections. Treatment of these infections
has become more difficult due to the emergence of multidrug-resistant strains. In particular,
methicillin-resistant S. aureus (MRSA), which was once restricted to hospitals, is spreading
rapidly through the community. Furthermore, resistance to vancomycin, the primary drug used to treat
MRSA, has also recently emerged.
Our research into S. aureus pathogenesis focuses on using clinically relevant strains to investigate the molecular mechanisms behind the emergence of low-level vancomycin resistance in this organism. We also have an interest in investigating the host-pathogen implications of vancomycin resistance, and the role of the Panton-Valentine leukocidin (PVL) in the pathogenesis of Australian MRSA and methicillin-sensitive S. aureus isolates. The molecular mechanisms resulting in the formation of clinically significant small colony variant (SCV) S. aureus strains along with the associated activation of an important bacterial stress response, known as the stringent response, has also become a recent focus. To achieve these aims we utilize a variety of molecular microbiology techniques including microarrays, whole genome sequencing, RNA sequencing (RNAseq), allelic exchange and protein function studies. Virulence studies using cellular invasion and persistence assays and the invertebrate S. aureus infection model Galleria mellonella are also used. ← Figure 3: Image taken from a heat map showing fold-changes in gene expression of VSSA compared with VISA. |
Figure 4. Electron micrograph of vancomycin sensitive (upper) and vancomycin intermediate (lower) Staphylococcus aureus (VSSA and VISA, respectively), showing thickening of the cell wall in the resistant isolate. |
Enterococcus faecium
Vancomycin resistant enterococci (VRE) are a major cause of serious hospital-acquired infections worldwide. In some Australian hospitals, while rates of MRSA infections have been decreasing, infections caused by VRE have significantly increased. The reasons for this increase are unknown. We have been using genomic approaches to investigate the evolution of VRE in Australia, focusing on Enterococcus faecium and trying to understand the molecular basis for the emergence of yet another hospital superbug.
Laboratory Staff
Figure 5: Our laboratory has been active in the application of
low-cost bacterial whole genome
sequencing and is using platforms
such as Illumina’s MiSeq instrument (left) and Ion Torrent’s Personal
Genome
Machine (right).
Head of Research Group
Associate Professor Tim Stinear: email: tstinear@unimelb.edu.au
Research staff (as of May 2012)
Dr Chris McEvoy (Postdoctoral Scientist)
Dr Liz Allwood (Postdoctoral Scientist)
Ms Ya-Hsun Li (Research Assistant)
Ms Jessica Porter (Research Assistant)
Mr Nicholas Tobias (PhD student)
Dr Kyra Chua (PhD student)
Mr Wei Gao (PhD student)
Ms Margaret Lam (PhD student)
Mr Justin Stepnell (PhD student)
Mr Ken Doig (MPhil student)
Ms Sarah Baines (MSc student)
Ms Rachel Howe (MSc student)
Ms Kirstie Mangas (Honours student)
Collaborators
Assoc Prof Benjamin Howden, Department of Infectious Diseases, Austin Health
Dr Torsten Seemann, Victorian Bioinformatics Consortium, Monash University
Prof Paul Johnson, Department of Infectious Diseases, Austin Health
Dr Grant Jerker Jenkin, Department of Infectious Diseases, Monash Medical Centre, Monash University
Dr Kellie Tuck, School of Chemistry, Monash University
Dr Kumar Visanathan, Centre for Inflammatory Diseases at Monash Medical Centre
Prof Gerd Pluschke, Swiss Tropical Public Health Institute in Basel
Dr Janet Fyfe, M. ulcerans WHO Collaborating Centre, Victorian Infectious Diseases Reference Laboratory
Prof Peter Leadlay, Department of Biochemistry, University of Cambridge, UK.
Dr Hui Hong, Department of Chemistry, University of Cambridge, UK.
Dr Caroline Demangel, PMI, Institut Pasteur, Paris
Assoc Prof Roland Brosch, PMI, Institut Pasteur, Paris
Dr Laurent Marsollier, Groupe d’étude des interactions hôtes-parasites, Université d’Angers, France
Dr John R Wallace, Department of Biology, Millersville University, PA, USA.
Prof John K Davies, Department of Microbiology, Monash University
Prof Jacques Schrenzel, Genomic Reseach Laboratory, University of Geneva Hospitals, Switzwerland
Dr Patrice Francois, Genomic Reseach Laboratory, University of Geneva Hospitals, Switzwerland
Prof Catherine Bennett, School of Health & Social Development, Deakin University
Figure 6: Optical maps derived from two strains of Enterococcus faecium →
Some useful links
For more information regarding polyketide synthases visit the site of Prof Peter Leadlay.
Prof Paul Johnson and the Victorian Government provide general information on Mycobacterium ulcerans and the disease it causes.
The Stop Buruli Initiative is a program of the UBS-Optimus Foundation to address key research priorities for Buruli ulcer.
BuruliList is a server hosted by the Institut Pasteur with the complete M. ulcerans genome sequence.
Burulivac is an initiative of the European Union to try and develop vaccines against Buruli ulcer.
Recent publications from the group can be found via this link
Our research is funded by:
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