CDC rethinking isolation for emerging staph strains

Full measures still needed on VISA confirmation

Infection control professionals should save the expensive isolation measures — including dedicated staff and culturing patient contacts — for only confirmed cases of vancomycin intermediate Staphylococcus aureus (VISA), Hospital Infection Control has learned. Unconfirmed VISA cases — as well as those involving staph strains with "reduced susceptibility" to vancomycin — can be placed in contact isolation similar to that used for methicillin-resistant S. aureus (MRSA), advisors to the Centers for Disease Control and Prevention recently determined.

While the CDC is slated to formally update its VISA measures by May 2001, the interim guidance came at a recent meeting of the Healthcare Infection Control Practices Advisory Committee (HICPAC). There have been six confirmed cases of VISA in the United States since 1997, but the CDC has confirmed 15 cases of the reduced- susceptibility strains in the last 18 months.

With roughly half the level of vancomycin resistance as VISA (MIC of 8), the reduced susceptibility stains are being commonly treated like MRSA in terms of infection control precautions. However, there apparently have been questions and some confusion on that issue. While they are similar to VISA, the expense of putting these cases into full-blown isolation would be considerable. Infection control measures for VISA are considerably more stringent than contact precautions, and include wearing masks, culturing contacts, and monitoring compliance with precautions. The full gamut of isolation measures including culturing contacts and using dedicated staff to enter rooms can cost up to $10,000 a case, Scott Fridkin, MD, a medical epidemiologist in the CDC’s division of healthcare quality promotion, told the HICPAC panel.

"That has been a real struggle for some people," said Fridkin, who with his colleagues fields questions and investigates reports of VISA that come into the CDC.

Would contact measures be enough?

Moreover, there has been no evidence of spread from hospitalized VISA patients, almost all of whom have been under contact precautions for a preexisting MRSA infection. So Fridkin raised the possibility of placing all VISA cases and the other less resistant strains under contact isolation. "We have seen no evidence of transmission, so I am proposing that contact precautions would probably be fine," he said. In addition, one of the initial justifications for the stringent guidelines was that the mechanism of resistance in the VISA isolates might be transferred genetically to other pathogens. That concern has not been borne out in laboratory work with the isolates.

"Do we need to go to these special precautions above and beyond contact precautions — like we would for MRSA — for an organism that we don’t have any evidence is being spread?" Fridkin asked the panel. "Now we know a little bit more about the resistance elements, and it is not a bug that is going to hop around a lot."

However, William Scheckler, MD, a HICPAC member, warned that scaling down the VISA precautions would be "way ahead of the data" because only six cases have occurred in the United States.

HICPAC chairman Robert Weinstein, MD, struck something of a compromise in offering a summary position that the panel found acceptable.

"Since at this point, there are only six isolates confirmed [of VISA in the United States], I would be willing to tell people that have not confirmed the isolate they can treat it like MRSA," Scheckler said. "Once it is confirmed, we still only have six bugs, six experiences. I don’t think I would change the interim guidelines for a confirmed [VISA] isolate. Let us deal with that with the new guidelines that will be coming out [in May]."