A nosy bacteria
Staphylococcus aureus, "staph," loves the warm, moist lining of our noses. About a third of us host staph colonies at any given time, and nasal colonization can be a risk factor for infection.
When infectious disease researchers began seeing cases of methicillin-resistant S. aureus (MRSA) in the community, they wondered: was there a reservoir of MRSA lurking in people's noses, says C. Buddy Creech, M.D., M.P.H., a pediatric infectious disease specialist at Vanderbilt.
In 2001, Mari Nakamura, M.D., a resident at the time, and Kathryn Edwards, M.D., professor of Pediatrics, swabbed the noses of 500 healthy children in the Vanderbilt Pediatric Primary Care Clinic and at the private offices of Old Harding Pediatrics in Nashville, to look for staph and particularly MRSA. In the group of 500, 145 children (29 percent) were colonized with S. aureus, and four of those had MRSA.
"There wasn't a terrific amount of MRSA in kids' noses, but it was out there," Creech says.
After what he calls "a barrage of MRSA cases," Creech and Edwards decided to repeat the study in 2004 – they swabbed the same number of children at the same two pediatrics practices. This time around, they found that 46 children had MRSA in their noses, more than a tenfold increase in just three years.
"This was really remarkable," Creech says. "I wouldn't be surprised if five years from now most of the staph we carry happens to be methicillin-resistant."
It is unclear if individuals carrying MRSA are at increased risk for infections, Creech says. He points to evidence from a military study suggesting that may be the case – soldiers who started basic training with MRSA nasal colonization were 10 times more likely to get an infection compared to trainees with "old-fashioned" staph.
More MRSA lurking about in our communities is particularly worrisome in the setting of a potential flu epidemic, Creech says. It's known that staph prefers to infect flu-altered lung linings – the resulting bacterial pneumonia might be especially deadly if the bacteria are MRSA. VM
- Leigh MacMillan