CDC steps up SEARCH for resistant staph isolates

Alarmed by emerging vancomycin resistance in strains of Staphylococcus aureus, the Centers for Disease Control and Preven tion is upgrading surveillance for the patho gen and urging clinicians to submit isolates for confirmation.

Since the first strains of glycopeptide (vancomycin) intermediate-resistant S. aureus (GISA) were reported in Japan and the United States, concerns have increased that full-blown resistance to the last-line drug could arise in staph strains. (See Hospital Infection Control, October 1997, pp. 145-152.) Julie Gerberding, MD, MPH, director of the CDC hospital infections program, recently reiterated those concerns in Baltimore at the annual meeting of the Association for Professionals in Infection Control and Epidemiology.

Hoping the pipeline will catch up

"We all need to be on the alert for Staph aureus with reduced susceptibility to vancomycin and jump on these organisms as quickly as we can," she said. "If we don’t, we will see the full emergence of vancomycin-resistant Staph aureus sooner rather than later. Our goal is not realistically to prevent this from occurring, but to delay it for as long as we possibly can and hope against hope that the pipeline in the pharmaceutical industry will catch up to our urgent clinical needs."

To that end, the CDC has created SEARCH (Surveillance for Emerging Antimic robial Resistance Connected to Health care). SEARCH is a network of voluntary participants (i.e., hospitals, private industries, professional organizations, and state health departments) joined together to report the isolation of S. aureus with reduced susceptibility to vancomycin. All U.S. health care organizations or practitioners are encouraged to report such isolates to the program, and after notifying their state health departments, to send the isolates to CDC for confirmatory testing. The program is using the following definitions and reporting protocol:

Definitions: S. aureus with reduced susceptibility to vancomycin: Isolates having a minimum inhibitory concentration (MIC) to vancomycin of greater than or equal to 4 µg/ml. This definition includes isolates determined to be glycopeptide (vancomycin) intermediate-resistant S. aureus (GISA/VISA; MIC= 8-16 µg/ml). Glycopeptide (vancomycin) -resistant S. aureus (GRSA/VRSA): Isolates of S. aureus that have a vancomycin MIC greater than or equal to 32 µg/ml.

Reporting isolates: Notify your state health department before reporting or sending an isolate to CDC for confirmatory testing. Test the isolate on two separate occasions using acceptable quantitative methods to detect a vancomy cin MIC of greater than or equal to 4 µg/ ml after 24 hours of incubation. Acceptable methods include broth microdilution (e.g., MicroScan Conventional, Vitek, Sensititre, Pasco), Etest, and agar dilution. Disk diffusion is not an acceptable method. When these criteria are met, send an e-mail to SEARCH@cdc.gov with your name, title, phone number, and fax number. You will receive an information sheet that must be included with the isolate sent in for confirmatory testing.