Staphylococcus aureus VISA

It has been a decade since hospital-acquired vancomycin-resistant Staphylococcus aureus (VRSA) was first isolated from the catheter tip of a dialysis patient in Michigan.  But that was 30 years after methicillin-resistant Staphylococcus aureus (MRSA) was initially reported—largely because methicillin was more widely prescribed for a longer time.  But how did S. aureus evolve resistance to this “last line” antibiotic?  Harvard researchers have now determined that S. aureus acquired either a plasmid or a transposon from one or another Enterococcus strains that colonize the host’s gut. Most interestingly, these investigators found that all twelve known strains of VRSA have evolved independently of each other, which suggests that within personalized medicine reside personalized pathogens.      MORE

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