The evolution of methicillin resistance in Staphylococcus aureus : Similarity of genetic backgrounds in historically early methicillin-susceptible and -resistant isolates and contemporary epidemic clones

Abstract

The key genetic component of methicillin resistance, the mecA determinant, is not native to Staphylococcus aureus. Thus, the evolution of methicillin-resistant S. aureus (MRSA) must have begun with the acquisition of the mecA determinant from an unknown heterologous source some time before the first reported appearance of MRSA isolates in clinical specimens in the U.K. and Denmark (in the early 1960s). We compared the genetic backgrounds and phenotypes of a group of methicillin-susceptible S. aureus (MSSA) isolates to the properties of MRSA strains isolated in Denmark and the U.K. during the same time period, and also to the genetic profiles of contemporary epidemic clones of MRSA. All early MRSA isolates resembled a large group of the early MSSA blood isolates in phenotypic and genetic properties, including phage group, antibiotype (resistance to penicillin, streptomycin, and tetracycline), pulsed-field gel electrophoresis pattern, and spaA type and multilocus sequence type, strongly suggesting that the early MSSA examined here represented the progeny of a strain that served as one of the first S. aureus recipients of the methicillinresistance determinant in Europe. The genetic background of this group of early MSSA isolates was also very similar to that of the widely disseminated contemporary ''Iberian clone'' of MRSA, suggesting that genetic determinants present in early MSSA and essential for some aspects of the epidemicity and͞or virulence of these strains may have been retained by this highly successful contemporary MRSA lineage.

Evolution of Sporadic Isolates of Methicillin-Resistant Staphylococcus aureus (MRSA) in Hospitals and Their Similarities to Isolates of Community-Acquired MRSA

“…MLST was performed according to a previously described procedure (13), with the exception of primer arcCF2 (5Ј-CCT TTA TTT GAT TCA CCA GCG-3Ј) (8). Sequences of both strands were determined by using an ABI Prism 310 genetic analyzer by using the BigDye fluorescent terminator chemistry (Applied Biosystems, Warrington, United Kingdom) at the DNA sequencing facilities at the Instituto Gulbenkian da Ciência, Oeiras, Portugal, or by using ABI Prism 3700 genetic analyzers at The Rockefeller University, New York, N.Y., and Macrogen, Seoul, South Korea.…”

High prevalence of ST121 in community-associated methicillin-susceptible Staphylococcus aureus lineages responsible for skin and soft tissue infections in Portuguese children

“…The resulting SmaI patterns were analyzed by both visual inspection and automatically with BioNumerics software version 4.61 (Applied Maths, Sint-Martens-Latem, Belgium) [14,15]. Characterization by spa typing, multilocus sequence typing (MLST), and the agr allele type were performed on representative isolates of each PFGE type [16][17][18]. The SCCmec was typed for all MRSA isolates [19,20].…”

Application of molecular techniques in the study of Staphylococcus aureus clonal evolution - A Review

“…It was first described as extensively disseminated in Hungarian hospitals , and later on, reported in hospitals in Thailand (Crisóstomo et al 2001).…”

“…The study allowed the identification of probable MSSA ancestors of the Archaic, Pediatric and NY/Japan MRSA clones (Crisóstomo et al 2001). However, studies involving more recent MSSA isolates (Mahmood et al 2002, Vivoni et al 2004 were not able to delineate associations between specific clones or CCs and the community or hospital origin of the isolates.…”