The multifaceted resources and microevolution of the successful human and animal pathogen methicillin-resistant Staphylococcus aureus.

Agnes Marie Sá Figueiredo,Fabienne Antunes Ferreira

doi:10.1590/0074-0276140016

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important bacterial pathogens based on its incidence and the severity of its associated infections. In addition, severe MRSA infections can occur in hospitalised patients or healthy individuals from the community. Studies have shown the infiltration of MRSA isolates of community origin into hospitals and variants of hospital-associated MRSA have caused infections in the community. These rapid epidemiological changes represent a challenge for the molecular characterisation of such bacteria as a hospital or community-acquired pathogen. To efficiently control the spread of MRSA, it is important to promptly detect the mecA gene, which is the determinant of methicillin resistance, using a polymerase chain reaction-based test or other rapidly and accurate methods that detect the mecA product penicillin-binding protein (PBP)2a or PBP2’. The recent emergence of MRSA isolates that harbour a mecA allotype, i.e., the mecC gene, infecting animals and humans has raised an additional and significant issue regarding MRSA laboratory detection. Antimicrobial drugs for MRSA therapy are becoming depleted and vancomycin is still the main choice in many cases. In this review, we present an overview of MRSA infections in community and healthcare settings with focus on recent changes in the global epidemiology, with special reference to the MRSA picture in Brazil.

Highlights

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important bacterial pathogens based on its incidence and the severity of its associated infections
The staphylococcal cassette chromosome mec (SCCmec) is integrated in the MRSA chromosome at the 3’ end of open reading frame X at the specific site attBSCC, which is located near the origin of replication in the staphylococcal chromosome and flanked by direct and repeated sequences
In contrast to livestock-associated MRSA (LA-MRSA), the majority of MRSA isolates that have been detected in pets have clustered into the sequence typing (ST) observed in community-acquired MRSA (CA-MRSA) strains commonly detected in humans (Ferreira et al 2011, Haenni et al 2012, Loeffler et al 2013). Since it was first described in the United Kingdom (UK) and Denmark in MRSA isolates from cattle harbouring SCCmec type XI, MRSA isolates carrying the mecC gene have been detected in a number of European countries (Cuny et al 2011, Garcia-Alvarez et al 2011, Shore et al 2011, Laurent et al 2012, Sabat et al 2012)

Summary

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important bacterial pathogens based on its incidence and the severity of its associated infections. Since it was first described in the UK and Denmark in MRSA isolates from cattle harbouring SCCmec type XI, MRSA isolates carrying the mecC gene have been detected in a number of European countries (Cuny et al 2011, Garcia-Alvarez et al 2011, Shore et al 2011, Laurent et al 2012, Sabat et al 2012).

Results

Conclusion