Objective: National surveillance of MRSA in New Zealand (NZ) has been undertaken for over 30 years. This surveillance provides basic epidemiological information on the prevalence of MRSA, geographic distribution, community- and hospital-associated MRSA, prevalent strains and resistance patterns.
Methods: Until 1998 national MRSA surveillance was continuous and based on referral of all MRSA isolates to the national reference laboratory for strain typing. Since 2000, MRSA surveillance has been based on annual surveys. Key patient data is collected with the referred isolates.
Results: Until the mid-1990s, MRSA were uncommon in NZ and accounted for only about 1% of S. aureus isolates. The prevalence of MRSA then increased steadily and by 2006 was 8%. Initially most of this increase was due to the emergence and spread of the community-associated, non-multiresistant WSPP MRSA (ST30 SCCmec IV). In 2000, the EMRSA-15 strain (ST22 SCCmec IV) started to spread in NZ healthcare facilities and by 2002 was more common than WSPP MRSA. Over the last 2-3 years, several new community-associated MRSA strains have emerged, including USA300. There has been a constant geographic variation in the prevalence of MRSA in NZ, with a north to south gradient and the highest rates in the northern areas. Due to the predominance of the WSPP and EMRSA-15 strains, most MRSA in New Zealand are not multiresistant.
Conclusions: Compared to many other countries, MRSA emerged later in NZ and is still relatively uncommon in many areas of the country. Initially MRSA was more likely to be community-acquired than hospital-acquired due to the predominance of the WSPP strain. With the establishment of the EMRSA-15 strain, MRSA is now frequently isolated from patients in healthcare facilities in some parts of the country.