Superbug study shows increased risk

01 May 2013

New Zealander’s are at double the risk of catching the superbug MRSA than they were six years ago and now more likely to be infected in the community than in hospitals.

Those are some of the conclusions from the first study to systematically assess the impact of MRSA in New Zealand. (MRSA is an antibiotic resistant Staphyloccus bacteria).

The results of the study were published this week in the international PLOS ONE scientific journal. The study was led by Dr Helen Heffernan from the Institute of Environmental Science and Research (ESR) in Wellington.

The co-authors included Dr Deborah Williamson, Dr Stephen Ritchie, and Professor John Fraser from the Faculty of Medical and Health Sciences at The University of Auckland, and Sally Roberts from the Department of Clinical Microbiology at the Auckland District Health Board.

While New Zealand’s rate of MRSA is low compared to other countries, the new study shows that the incidence of the bacteria has doubled here in the six years to 2011. It found that the specimens across the population increased from 8.6 to 18 per 100,000 people between 2005 and 2011.

Building on ESR’s regular surveillance, the research team used hospital admission data recorded by the New Zealand Ministry of Health to look at additional demographic data such as ethnicity, number of previous hospitalisations in the preceding year, and socioeconomic status based on the New Zealand deprivation index.

Dr Williamson said that for clinicians and patients it was encouraging that the rates remained comparatively low.

“The data is very helpful in highlighting the groups affected by MRSA, and it also provides valuable information for health care providers on the circulating strains. As a country we should be encouraged that we have the capacity to do this type of surveillance so well,” she said.

Among the demographic and epidemiological findings, the report noted that when MRSA first arose globally around 20 years ago, it was a ‘hospital bug’.

MRSA was now more associated with infections in people in the community, both globally and in New Zealand, where there was a significant increase in community associated MRSA in recent years.

This was largely due to two clones of the South-West Pacific MRSA. Another clone identified for the first time in the 2005 survey had rapidly became the predominant community associated MRSA strain in New Zealand.

The shift to community associated MSRA was also accompanied by a rise in cases among younger age groups, especially in recent years.

The less rapid increase in hospital associated MRSA could be the result of an increased focus of prevention measures in hospitals to combat bacteria such as MRSA, according to the report. It was also noted that MRSA rates were significantly higher in Maori and Pacific Island populations.

This was in keeping with findings for other infectious diseases where these populations carry a greater burden. Maori and Pacific Peoples ethnic groups disproportionately carried the burden of community associated MRSA.

Dr Williamson said the study would not have been possible without New Zealand’s national surveillance system to comprehensively monitor MRSA which many countries do not have.

“This system allows us to do this important research into MRSA because isolates and data are collected consistently each year and from all diagnostic microbiology laboratories in New Zealand, providing a nationally representative profile of the epidemiology of MRSA.”

For more information, the PLOS ONE paper is available online .

For more information contact:

Suzi Phillips Media Relations Advisor The University of Auckland s.phillips@auckland.ac.nz Mob 021 416 396 Phone +64 9 373 7599 ext 87383