The July 5th edition of the Centers for Disease Control and Prevention's (CDC) Morbidity and Mortality Weekly Report (MMWR) contains the report of the first documented case of infection caused by vancomycin-resistant Staphylococcus. aureus (VRSA). Following is a summary of that report:

S.aureus is the most common cause of hospital-acquired infections. The first clinical isolate of this pathogen that had a reduced susceptibility to vancomycin ("vancomycin-intermediate" S. aureus, or VISA) was reported in Japan in 1996. As of June 2002, eight patients in the United States have been confirmed as having clinical infections caused by VISA. This report describes the first documented case of infection by vancomycin-resistant S. aureus (VRSA), which was isolated from a swab received from that patient in June 2002.

The patient was a dialysis patient who had received multiple courses of antibiotics since April 2001 for chronic foot ulcers, and had an MRSA bacteremia in April 2002 associated with a hemodialysis graft. In June 2002, a swab of an infected foot ulcer yielded VRE, K. oxytoca and vancomycin-resistant S. aureus (VRSA). MICs to vancomycin and teicoplanin were 128 and 32 µg/ml, respectively, and analysis at the CDC identified that the isolate contained the vanA gene.

Epidemiologic and laboratory investigations are under way to assess the risk for transmission of VRSA to other patients, health-care workers, and other contacts. To date, no VRSA transmission has been identified.

This is the first description of what microbiologists and infection control staff have been dreading for a decade: the acquisition of the vanA gene, most likely from a VRE, by and MRSA strain. That this is the first isolate identified hopefully means that such acquisition is rare; however, it also means that it may occur. Its existence should give new impetus to programs in Canada to reduce the incidence of both MRSA and VRE and minimize opportunities for the emergence of this resistance. It also emphasizes the need within microbiology laboratories to continue surveillance for vancomycin resistance in S. aureus, particularly in high-risk patients. As always, the isolation of S. aureus with confirmed or presumptive vancomycin resistance should be reported immediately through local and provincial health departments to the Population and Public Health Branch of Health Canada.

The full report on Vancomycin-resistant Staphylococcus aureus can be downloaded in a PDF form of the entire MMWR newsletter here, and viewed in HTML form on the CDC website here.