MRSA
Staphylococcus aureus (S. aureus) is a bacterium found as part of the normal human flora, often found in the upper respiratory tract and on the skin. In most cases S. aureus does not pose a health risk; however, it is an opportunistic pathogen. If S. aureus enters the bloodstream or internal tissues, it can be life-threatening. Multidrug resistant S. aureus such as methicillin-resistant S. aureus (MRSA), present significant challenges due to its virulence mechanisms and the difficulty of establishing a universal treatment plan. Delineating infections acquired in healthcare settings (HA-MRSA) from those acquired in the community (CA-MRSA) is increasingly challenging and shifts in antimicrobial resistance profiles between different populations pose challenges to treatment. Thus, MRSA is a pathogen of public health concern in both healthcare and community environments.
MRSA carries a mec gene. This gene is part of a cassette, SCCmec (Staphylococcal chromosomal cassette mec), and is a primary mechanism for resistance to methicillin and other β-lactam antibiotics. There are several SCCmec types, all of which confer resistance to different and multiple antibiotics. SCCmec types have been shown by Guthrie et al. to have been changing over time in Ontario, Canada with the shift in MRSA clonal complexes.