Drug-resistant bacteria MRSA a growing threat

Mar 21 2005

Infectious diseases researchers at Vanderbilt University Medical Center are noticing a significant increase in the number of infections due to Methicillin-Resistant Staphylococcus Aureus (MRSA) and the number of asymptomatic individuals who harbor the organism in their bodies.

In fact, in a recent analysis of children seen in 2003 at the emergency department of the Monroe Carell Jr. Children's Hospital at Vanderbilt, approximately 60 percent of the skin infections due to the staphylococcus germ were due to MRSA, an organism that can produce a variety of physical manifestations across a spectrum, from the very minor, all the way to causing death. Now a new study done by VUMC researchers confirms a dramatic spread of the organism that is being harbored in the noses of healthy children.

"What this tells us is that we're more likely to find MRSA in this population than we are the typical staphylococcus organism that is susceptible to methicillin," said Buddy Creech, M.D., a fellow in pediatric infectious diseases and the lead investigator on the study. "The problem with this organism is that it seems to behave differently, with a tendency to cause skin abscesses and pneumonia."

According to the Centers for Disease Control and Prevention (CDC), MRSA is a type of bacteria that is resistant to a class of antibiotics that include methicillin and other more commonly prescribed variants such as oxacillin, amoxicillin and other penicillin-based drugs. Previously MRSA was seen only in the hospital in patients with underlying diseases or compromised immune systems. Now the organism appears to be common among people everywhere, including those in communal settings such as the military, prisons, daycare facilities, and on athletic teams. The CDC estimates that roughly 130,000 people are hospitalized with MRSA each year.

MRSA can enter the body through even the smallest opening in the skin and infiltrate the bloodstream. Once MRSA enters the bloodstream the bacteria can cause devastating staph infections.

The organism can be difficult to control because its early symptoms are so benign, and because those who are infected frequently delay seeking medical intervention until the organism has begun to spread.

Creech and colleagues visited one of Nashville's large community pediatric practices, and the Vanderbilt Children's Hospital Outpatient Pediatric Clinic, to swab the noses of 500 otherwise healthy children to collect samples. Three years earlier a similar study had been done in the same practices and Creech wanted to see whether things had changed.

"We were just trying to get a sense of how common MRSA actually is in the community," he said. "We've known for over a half century that staphylococcus likes to live in the nose and that's where it thrives. If it's not in the nose, you probably don't have it. So we went out and collected these samples."

What Creech and colleagues discovered was that 9.2 percent of the children from this sampling were positive for MRSA in their noses. "That's up dramatically from three years ago when only 1 percent had MRSA," he said.

"What we are able to show is that the increasing incidence of this organism is not just an isolated phenomenon among football players, prisoners and others in close communal settings," he said. "These are young healthy children who are coming in for well child visits and they have the resistant organisms in their noses."

Creech says the next mystery to be solved is why MRSA is increasing in healthy people.

"This study tells us there are a lot of children walking around with MRSA who are healthy, but we are also seeing this germ cause infections. What we are trying to understand is why some children go on to develop a serious infection and others don't."

Vanderbilt Children's Hospital has had adolescents in the intensive care units suffering from pneumonia and others with the organism in the bloodstream. MRSA skin abscesses, the typical problem associated with MRSA, and bone infections have also been seen in both the Emergency Department and outpatient clinics. The skin abscesses often require drainage and antibiotics.

"We are yet to understand why some children just have MRSA in their nose, causing no disease, while others are severely ill," he said. Still, Creech says parents should not be alarmed but consult their physician if their child develops skin infections, fever or other signs of illness.