Could masking workers block MRSA colonization?

No nares colonization found in masked residents

Wearing surgical masks for the care of patients under isolation for methicillin-resistant Staphylococcus aureus (MRSA) may be an important factor in preventing colonization in health care workers, an epidemiologist has found. While masks are not typically worn for the care of MRSA patients in contact isolation, she found that medical residents who were following such a policy were not colonized with the nosocomial pathogen.

"We had no residents colonized with MRSA, which I think is a very interesting finding in that at the institution where this was done, they were using masks as part of their isolation from MRSA," says Tobi Karchner, MD, MS, assistant professor of medicine at the University of Maryland in College Park.

"We were actually very pleased to find that none of the residents were colonized with MRSA. The residents were hesitant to let us do it because everybody was afraid they were going to be colonized. We would expect a low prevalence of health care workers to be colonized, but one of the things we were trying to look at is, if you’re masked, is it even lower?"

No one positive for resistant staph

To conduct the study, cultures from the anterior nasal area of 80 medical residents were obtained over a one-week period at a hospital in central Virginia that routinely used masks as part of contact/droplet isolation for MRSA patients. Overall, 38 (48%) of the 80 were positive for methicillin-sensitive S. aureus, but none were positive for MRSA. Despite the hospital having experienced an increase in MRSA patients, MRSA was not found in the workers, suggesting that wearing masks may be an important measure for the prevention of colonization, she says.

Citing personal communication, Karchner says another hospital where such masking is not routine had a 3.4% of workers colonized with MRSA. A published study also found that 12 of 26 workers wearing gowns and gloves — but not masks — while working with MRSA patients became transiently colonized with MRSA in their nares on 36 occasions over a seven-week period.¹ "They also didn’t use masks, and they found that [about] half of the nurses became transiently colonized at some point," she says.

Both patients and workers who are nasal carriers of MRSA have been shown to disperse organisms and can be a potential source of spread, she adds. Of interest, the Centers for Disease Control and Prevention has recommended that workers don masks for patients under isolation for the emerging strains of vancomycin-intermediate-resistant S. aureus. That recommendation essentially took the position of "pulling out all of the stops" due to concern over that organism. (See Hospital Infection Control August 1997, pp. 113-118.)

"It seems like if you’re going to do that, then maybe we should be more aggressive and do everything that we can possibly do for MRSA, too," Karchner says. "That sort of makes sense to me, but not everybody agrees on that. This is the beginning of data [on this]. I am trying to replicate the study at a few other places."

Reference

1. Cookson B, Peters B, Webster M, et al. Staff carriage of epidemic methicillin-resistant Staphylococcus aureus. J Clin Microbiol 1989; 27:1,471-1,476.