Clinical and Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in New Zealand: Rapid Emergence of Sequence Type 5 (ST5)-SCCmec-IV as the Dominant Community-Associated MRSA Clone

Deborah A Williamson,Sally A Roberts,Stephen R Ritchie,Helen Heffernan,Geoffrey W Coombs,John D Fraser,Herminia De Lencastre

doi:10.1371/journal.pone.0062020

Abstract

The predominant community-associated MRSA strains vary between geographic settings, with ST8-IV USA300 being the commonest clone in North America, and the ST30-IV Southwest Pacific clone established as the dominant clone in New Zealand for the past two decades. Moreover, distinct epidemiological risk factors have been described for colonisation and/or infection with CA-MRSA strains, although these associations have not previously been characterized in New Zealand. Based on data from the annual New Zealand MRSA survey, we sought to describe the clinical and molecular epidemiology of MRSA in New Zealand. All non-duplicate clinical MRSA isolates from New Zealand diagnostic laboratories collected as part of the annual MRSA survey were included. Demographic data was collected for all patients, including age, gender, ethnicity, social deprivation index and hospitalization history. MRSA was isolated from clinical specimens from 3,323 patients during the 2005 to 2011 annual surveys. There were marked ethnic differences, with MRSA isolation rates significantly higher in Māori and Pacific Peoples. Over the study period, there was a significant increase in CA-MRSA, and a previously unidentified PVL-negative ST5-IV spa t002 clone replaced the PVL-positive ST30-IV Southwest Pacific clone as the dominant CA-MRSA clone. Of particular concern was the finding of several successful and virulent MRSA clones from other geographic settings, including ST93-IV (Queensland CA-MRSA), ST8-IV (USA300) and ST772-V (Bengal Bay MRSA). Ongoing molecular surveillance is essential to prevent these MRSA strains becoming endemic in the New Zealand healthcare setting.

Highlights

The global emergence of community-associated methicillinresistant Staphylococcus aureus (CA-methicillin-resistant Staphylococcus aureus (MRSA)) over the past two decades has been well described [1]
The predominant community-associated methicillinresistant Staphylococcus aureus (CA-MRSA) vary between geographic settings, with USA300 the overwhelmingly dominant CA-MRSA clone in North America, and the ST93 Queensland CA-MRSA clone emerging as the most common CAMRSA clone in Australia [2,3]
Using hospital admission data recorded by the New Zealand Ministry of Health, the following additional demographic information was extracted about each patient: ethnicity, number of previous hospitalizations in the preceding year, and socioeconomic status based on the New Zealand deprivation index (NZDep)

Summary

Introduction

The global emergence of community-associated methicillinresistant Staphylococcus aureus (CA-MRSA) over the past two decades has been well described [1]. The epidemic spread of the USA300 clone throughout North America has resulted in considerable morbidity, with several studies describing increasing rates of emergency department attendances and hospitalizations for CA-MRSA-associated skin and soft tissue infections (SSTI) [4,5]. Initial reports of CA-MRSA strains described the emergence of these strains in patients with a lack of traditional epidemiological risk factors for MRSA infection and/or colonization [6]. Distinct socio-demographic associations have been described for CA-MRSA infection, including ethnicity, socioeconomic deprivation and incarceration [1]. As the prevalence of CA-MRSA strains has increased, the epidemiological distinction between these strains and HCA-MRSA strains has become less well defined, with numerous reports of nosocomial outbreaks of infections due to CA-MRSA strains [9,10]

Methods

Results

Conclusion