Staphylococcus aureus Infections in New Zealand, 2000–2011

Deborah A. Williamson

, Jane Zhang, Stephen R. Ritchie, Sally A. Roberts, John D. Fraser, and Michael G. Baker

Author affiliations: University of Auckland, Auckland, New Zealand (D.A. Williamson, S.R. Ritchie, J.D. Fraser); Institute of Environmental Science and Research, Wellington, New Zealand (D.A. Williamson); University of Otago, Wellington (J. Zhang, M.G Baker); Auckland District Health Board, Auckland (S.A. Roberts)

Abstract

The incidence rate for invasive and noninvasive Staphylococcus aureus infections in New Zealand is among the highest reported in the developed world. Using nationally collated hospital discharge data, we analyzed the epidemiology of serious S. aureus infections in New Zealand during 2000–2011. During this period, incidence of S. aureus skin and soft tissue infections increased significantly while incidence of staphylococcal sepsis and pneumonia remained stable. We observed marked ethnic and sociodemographic inequality across all S. aureus infections; incidence rates for all forms of S. aureus infections were highest among Māori and Pacific Peoples and among patients residing in areas of high socioeconomic deprivation. The increased incidence of S. aureus skin and soft tissue infections, coupled with the demographic disparities, is of considerable concern. Future work should aim to reduce this disturbing national trend.

Despite advances in diagnostics and therapeutics, the clinical and economic burdens ofStaphylococcus aureus infections remain a substantial public health problem (1). During the past decade in several parts of the world, most notably in North America, the epidemiology of S. aureus infections has changed dramatically, predominantly because of the epidemic spread of a strain of community-associated methicillin-resistant S. aureus (MRSA) (2,3). Infections caused by community-associated MRSA are most commonly skin and soft tissue infections (SSTIs) and typically occur in patients with no history of exposure to health care facilities (1). In addition, specific sociodemographic associations for community-associated MRSA infection have been described and include younger patient age, specific ethnic groups, and economic deprivation (1,4,5). Although the epidemiology of S. aureus infections has been well studied in North America, comparatively little is known about the trends and patient demographics for S. aureusinfections in other geographic settings, particularly in the Southern Hemisphere. Knowledge of the overall prevalence and distribution of S. aureus infections, regardless of methicillin resistance, at a population level is crucial for informing prevention and control strategies.

The incidence of invasive and noninvasive S. aureus infections is reportedly higher In New Zealand than in other developed countries; rates are highest among Māori (indigenous New Zealanders) and Pacific Peoples (6–9). For example, in 1 study, S. aureus bacteremia was 2 times more likely to develop among Māori patients and 4 times more likely to develop among Pacific Peoples than among European patients (7). To date, however, studies describing S. aureus infections in New Zealand have generally been confined to 1 geographic region, to children, or to 1 specific aspect of S. aureus disease such as bloodstream or MRSA infection (4,6–8). Accordingly, we sought to describe the longitudinal trends for S. aureus infection and demographic characteristics of patients across the entire New Zealand population for the 12-year period 2000–2011.

Acknowledgments

This study was supported by internal funding.

Dr Williamson is a clinical microbiologist and a clinical research training fellow of the Health Research Council of New Zealand. Her research interests are the clinical and molecular epidemiology of S. aureus infections and infections caused by antimicrobial drug–resistant pathogens.

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Suggested citation for this article: Williamson DA, Zhang J, Ritchie SR, Roberts SA, Fraser JD, Baker MG. Staphylococcus aureus infections in New Zealand, 2000–2011. Emerg Infect Dis [Internet]. 2014 Jul [date cited]. http://dx.doi.org/10.3201/eid2007.131923