Development of decreased susceptibility to daptomycin and vancomycin in a Staphylococcus aureus strain during prolonged therapy.

60 years following the primary isolation of the Oxford Staphylococcus. From an evolutionary perspective, it is noteworthy that members of this clonal lineage have subsequently acquired methicillin resistance [specifically following acquisition of the staphylococcal chromosome cassette mec (SCCmec) type IV element] and emerged as a community-associated MRSA strain (ST30MRSA-SCCmecIV) which has been found in the Southwest Pacific and some other regions, including the UK. The Oxford Staphylococcus has been used as a control organism for some 60 years and we are not aware of any infections resulting from acquisition of this organism by laboratory personnel. Although the provenance of the control strain is unclear, it is tempting to speculate that it was originally isolated from a pyogenic infection associated with the presence of the PVL genes. It may be argued that the organism may have become attenuated following repeated subculture over the years following its initial isolation. Nevertheless, these observations serve as an alert to microbiologists: good laboratory practice should be adhered to where this organism is handled, particularly following the report of infection due to PVL-positive MRSA occurring in a microbiologist working with such organisms. Attention should be paid to the covering of cuts and wounds and/or wearing of gloves to minimize any risk of infection among laboratory workers. Crucially, healthcare personnel should remain vigilant to the possible occurrence of SSTIs in individuals handling the Oxford Staphylococcus and, where S. aureus is identified as the aetiological agent, the isolate should be fully characterized to determine its PVL status and relatedness to the control strain.