Staphylococcus aureus is a cause of hospital and community acquired infections (1,2). In 1996, the first clinical isolate of S. aureus with reduced susceptibility to vancomycin was reported from Japan (3). The vancomycin minimum inhibitory concentration (MIC) result reported for this isolate was in the intermediate range (vancomycin MIC 8 µg/mL) using interpretive criteria defined by the National Committee for Clinical Laboratory Standards (4). As of June 2002, eight patients with clinical infections caused by vancomycin-intermediate S.aureus (VISA) have been confirmed in the United States (5,6). This report describes the first documented case of infection caused by vancomycin-resistant S.aureus (VRSA) (vancomycin MIC >32 µg/mL) in a patient in the USA. The emergence of VRSA underscores the need for programs to prevent the spread of antimicrobial resistant microorganisms and control the use of antimicrobial drugs in health care settings.

In June 2002, VRSA was isolated from a swab obtained from a catheter exit site from a Michigan resident aged 40 years with diabetes, peripheral vascular disease, and chronic renal failure. The patient received dialysis at an outpatient facility (dialysis center A). Since April 2001, the patient had been treated for chronic foot ulcerations with multiple courses of antimicrobial therapy, some of which included vancomycin. In April 2002, the patient underwent amputation of a gangrenous toe and subsequently developed methicillin resistant S.aureus bacteremia caused by an infected arteriovenous hemodialysis graft. The infection was treated with vancomycin, rifampin, and removal of the infected graft. In June, the patient developed a suspected catheter exit-site infection, and the temporary dialysis catheter was removed; cultures of the exit site and catheter tip subsequently grew S.aureus resistant to oxacillin (MIC >16 µg/mL) and vancomycin (MIC >128 µg/mL). A week after catheter removal, the exit site appeared healed; however, the patient's chronic foot ulcer appeared infected. VRSA, vancomycin resistant Enterococcus faecalis (VRE), and Klebsiella oxytoca also were recovered from a culture of the ulcer. Swab cultures of the patient's healed catheter exit site and anterior nares did not grow VRSA. To date, the patient is clinically stable, and the infection is responding to outpatient treatment consisting of aggressive wound care and systemic antimicrobial therapy with trimethroprim/sulfamethoxazole.

The VRSA isolate recovered from the catheter exit site was identified initially at a local hospital laboratory using commercial MIC testing and was confirmed by the Michigan Department of Community Health and the Centers for Disease Control and Prevention (CDC). Identification methods used at CDC included traditional biochemical tests and DNA sequence analysis of gyrA and the gene encoding 16S ribosomal RNA. Molecular tests for genes unique to enterococci were negative. The MIC results for vancomycin, teicoplaninin, and oxacillin were >128 µg/mL, 32 µg/mL, and >16 µg/mL, respectively, by the broth microdilution method. The isolate contained the vanA vancomycin resistance gene from enterococci, which is consistent with the glycopeptide MIC profiles. It also contained the oxacillin-resistance gene mecA. The isolate was susceptible to chloramphenicol, linezolid, minocycline, quinupristin/dalfopristin, tetracycline, and trimethoprim/sulfamethoxazole.

Epidemiological and laboratory investigations are under way to assess the risk for transmission of VRSA to other patients, health care workers, and close family and other contacts. To date, no VRSA transmission has been identified. Infection control practices in dialysis center A were assessed; all health-care workers followed standard precautions consistent with CDC guidelines (7). After the identification of VRSA, dialysis center A initiated special precautions on the basis of CDC recommendations (8), including using gloves, gowns, and masks for all contacts with the patient; performing dialysis with a dedicated dialysis machine during the last shift of the day in an area separate from other patients; having a dialysis technician dedicated to providing care for the patient; using dedicated, noncritical patient care items; and enhancing education of staff members about appropriate infection-control practices. Assessment of infection control practices in other health-care settings in which the patient was treated is ongoing.

Reported by: DM Sievert, et al, at Michigan Dept of Community Health; W Brown, et al, at Detroit Medical Center; R Johnson, Detroit; J Mitchell, Oakwood Health Care System, Dearborn, Michigan. Div of Healthcare Quality Promotion, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; S Chang, CDC.

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