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Molecular characterization and clonal diversity of meticillin-resistant Staphylococcus aureus isolated from the community in Spain: emergence of clone sequence type 72

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Summary

Sequence type 72 meticillin-resistant Staphylococcus aureus (ST72 MRSA) was recently detected in our hospital. Although in Europe this clone is rarely isolated, it is the leading cause of community-associated MRSA infections in Korea, spreading also into hospitals, where it has also emerged as the main MRSA clone recovered from raw meat. We studied MRSA isolated from outpatients in Spain during a nine-year period. More than 70% of the isolates belonged to predominant clones found in hospitals. There was a significant increase in the ST72 prevalence. It appears that boundaries of dominance among MRSA clones have become blurred, demanding continuous surveillance.

Introduction

Meticillin-resistant Staphylococcus aureus (MRSA) has been recognized as a major cause of infections worldwide, in hospital and community settings. Whereas hospital-associated MRSA (HA-MRSA) generally affects patients with predisposing risk factors, community-associated MRSA (CA-MRSA) generally affects healthy people without such risk factors.1, 2 Although the differences between HA-MRSA and CA-MRSA have become less distinct, HA-MRSA strains frequently contain SCCmec types I–III, and are mostly multidrug resistant. CA-MRSA isolates frequently carry smaller SCCmec elements (types IV–VII), often carry the Panton–Valentine leukocidin (pvl) genes, and are resistant to fewer classes of antimicrobials.2

Nowadays, however, HA-MRSA clones have been reported to cause infections in the community.3

Conversely, CA-MRSA has been increasingly identified as a cause of healthcare-associated infections, suggesting that certain clones have the ability to cross barriers between hospitals and the community.4 Thus, the epidemic CA-MRSA clone sequence type 72 (ST72) was recently detected in Complejo Hospitalario Universitario from Vigo, Spain.5 Although in Europe this clone is rarely isolated, ST72 has been established as the premier cause of CA-MRSA infections in Korea and it has disseminated into hospitals.6 Moreover, ST72 has emerged as the main MRSA clone recovered from raw meat in Korea.6

The information on MRSA in our community is scarce and the links between the hospital and community are not known. Because of the widespread ST72 clone, the aim of this study was to determine the current situation of the MRSA population isolated from the community setting in Spain.

Section snippets

Methods

This study was performed retrospectively on S. aureus isolated from outpatients attending 24 community healthcare centers in the north-west of Spain, serving a population of 300,000 between 2003 and 2011.

Staphylococcus aureus strains were isolated by standard techniques, and species identification and antibiograms were performed by Vitek2 (bioMérieux, Marcy L'Etoile, France).

Of the 4085 S. aureus isolates recovered, 457 (11%) were MRSA. The MRSA frequency ranged from 9% in 2003 to 20% in 2011.

Results

A total of 457 MRSA isolated from outpatients were typed. The different typing methods showed that the majority of isolates (331, 72.4%) were related to epidemic HA-MRSA clones, whereas 75 isolates (16.4%) were related to epidemic CA-MRSA clones, and 51 (11.2%) were sporadic. The HA-MRSA isolates were classified in five clonal groups: t067-ST125-IVc-agr2 (111 isolates, 24.3%), t002-ST5-IVc-agr2 (92 isolates, 20.1%), t018-ST36-II-agr1 (93 isolates, 20.3%), t032-ST22-IVc-agr1 (29 isolates, 6.3%),

Discussion

The data showed that MRSA isolated from outpatients did not represent an infrequent finding (average of 11% throughout the nine years studied). More than 70% of MRSA belonged to the most predominant clones found in hospitals, namely (ST125, ST36, ST5, ST22, and ST239). The international clone ST239 was endemic in our hospitals until 2002; that was then displaced by the epidemic clone ST36 (EMRSA-16), which was widespread in the UK.7 Currently, ST125 is predominant in Spanish hospitals and it is

Conflict of interest statement

None declared.

Funding source

Galician Health Services (SERGAS).

References (10)

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Results presented in part at the 24th European Congress of Clinical Microbiology and Infectious Diseases, Barcelona, Spain, May 10th to 13th, 2014; abstract 1243.

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