Menzies’ genetic fingerprinting methods were applied to describe the patterns of disease caused by S. aureus (golden staph) and determined that many strains circulate in the Top End. The type of disease caused depends on the strain and carriage of a toxin called Panton-Valentine leukocidin (PVL). The research found that approximately 50% of isolates in tropical northern Australia carry PVL and these caused disease in younger patients and had a tendency to cause large boils and abscesses, often requiring surgery. We are now considering using additional antibiotics to treat patients with severe staphylococcal disease caused by PVL+ strains.

We are leading a multicentre randomised controlled trial on alternative treatments for MRSA (resistant golden staph) bloodstream infections.  The mortality rate from MSRA infections is 20-30%. The antibiotic vancomycin is currently used as treatment and has a number of limitations.  The trial will test whether combining vancomycin with another antibiotic, flucloxacillin, will reduce the duration MRSA survives in the blood of patients with infections. This is a pilot study involving six hospitals across Australia – if the results from this trial are positive a larger trial will be conducted to validate the efficacy of treating MRSA patients with a combination of flucloxacillin and  vancomycin compared  with the traditional treatment regime of vancomycin alone.

Our studies on the population structure of S. aureus in the Northern Territory have lead to the discovery of a new Staphylococcus lineage, that is currently termed CC75. CC75 is commonly found in the Northern Territory, and appears particularly associated with skin lesions. Other researchers have very recently identified closely related strains in Cambodia, Polynesia, and tropical South America. In collaboration with the Wellcome Trust Genome Institute in the UK, we have analysed the entire genome sequence of one of these strains. Guided by this sequence, we determined that CC75 strains lack the golden pigment of conventional S. aureus, and consequently we now refer to CC75 using the provisional name “Staphylococcus argenteus” (silver staph). The population structure, ecology and virulence of S. argenteus are now under investigation.

2011 Highlights:
Research into golden staph identified that strains carrying the toxin PVL are particularly common in patients with severe staphylococcal infection in northern Australia.  We are now considering using additional antibiotics to treat patients with severe staphylococcal disease caused by strains containing the PVL toxin
In related molecular epidemiology Menzies’ new genetic fingerprinting technology was used to identify the nature of a cluster of antibiotic-resistant Enterococcus faecium infections at Royal Darwin Hospital

Staff: Phil Giffard, Steve Tong, Josh Davis, Rachael Lillebridge, Deborah Holt, Bart Currie