CDC warns fully resistant strains may now emerge

Stress detection, reporting, and control

In reporting the first two U.S. cases of vancomycin intermediate-resistant Staphylococcus aureus (VISA), the Centers for Disease Control and Prevention re-emphasized key recommendations for clinicians and infection control professionals, which are summarized as follows1-4:

• The emergence of VISA in the United States suggests that S. aureus strains with full resistance to vancomycin may eventually appear.

• These episodes emphasize the need to enhance laboratory capacity at the hospital and state levels to recognize these strains.

• To accurately detect staphylococci with reduced susceptibility to vancomycin, antimicrobial susceptibility should be determined with a quantitative method (broth dilution, agar dilution, or agar gradient diffusion) using a full 24 hours of incubation at 95° F (35° C). Strains of staphylococci with vancomycin minimum inhibitory concentrations (MIC) of 8 were not detected using disk-diffusion procedures. In both Michigan and New Jersey, VISA was detected by using a 24-hour MIC dilutional method that had not changed over the period during which these patients had repeated S. aureus infections.

• To prevent the spread of these organisms within and between facilities, health care providers and facilities are advised to ensure the appropriate use of vancomycin. Widespread use of antimicrobials, such as vancomycin, is a major contributing factor in the emergence of vancomycin-resistant organisms.

• Educate personnel who provide direct patient care on the epidemiologic implications of such strains and the infection-control precautions necessary for containment.

• Strictly adhere to and monitor compliance with contact isolation precautions and other recommended infection-control practices. In the first case, spread of VISA to other patients and health-care workers probably was prevented by prompt identification of the isolate and its susceptibility pattern, isolation of the patient while hospitalized, and implementation of recommended infection-control practices.

• The isolation of S. aureus with confirmed or "presumptive" reduced vancomycin susceptibility should be reported through state and local health departments to CDC’s Investigation and Prevention Branch, Hospital Infections Program, National Center for Infectious Diseases, Mail Stop E69, 1600 Clifton Road NE, Atlanta, GA 30333; telephone: (404) 639-6413. Physicians treating patients with infections caused by staphylococci with reduced susceptibility to vancomycin can obtain information about investigational drug therapies from the Food and Drug Administration’s Division of Anti-Infective Drug Products, telephone: (301) 827-2120.

References

1. Centers for Disease Control and Prevention. Staphylococcus aureus with reduced susceptibility to vancomycin — United States, 1997. MMWR 1997; 46:765-766.

2. Centers for Disease Control and Prevention. Update: Staphylococcus aureus with reduced susceptibility to vancomycin — United States, 1997. MMWR 1997; 46: 813-814.

3. Centers for Disease Control and Prevention. Interim guidelines for prevention and control of staphylococcal infection associated with reduced susceptibility to vancomycin. MMWR 1997; 46:626-628; 635.

4. Centers for Disease Control and Prevention. Recommendations for preventing the spread of vancomycin resistance: Recommendations of the Hospital Infection Control Practices Advisory Committee (HICPAC). MMWR 1995; 44:(no. RR-12)1-13.