Could coagulase negative staphylococci be an evolutionary source of resistance genes for Staphylococcus aureus?

Background The remarkable ability of Staphylococcus aureus to acquire mobile genetic elements that carry virulence and antibiotic resistance genes, contributes to its success, pathogenicity and evolution. There is indirect evidence that methicillinresistant S. aureus (MRSA) clones arose from genetic transfer of staphylococcal cassette chromosome mec (SCCmec) from Staphylococcus epidermidis and other coagulase-negative staphylococci (CNS) to methicillinsusceptible S. aureus (MSSA). These staphylococcal species are often co-located in human reservoirs such as the nose and this niche may provide an environment in which genetic transfer is favoured. The aim of this study was to demonstrate that methicillin-resistant coagulase-negative staphylococci (MRCNS) are commonly found in the nose of MRSA-positive patients and to provide evidence of antibiotic resistance gene transfer among these species.