Staph infections have risen by more than 90 percent, study finds


Published: Monday, November 30th, 2009

The number of cases of methicillin-resistant Staphylococcus aureus (MRSA) infections has increased by more than 90 percent over the last decade, according to recent research led by University scholars.
Ramanan Laxminarayan, a visiting scholar at the Princeton Environmental Institute, and Eili Klein, a visiting specialist in the ecology and evolutionary biology department, co-authored a paper on the spread of MRSA infections from 1999 through 2005.

In 2006, there were 278,203 reported cases of MRSA-related infection, more than double the number in 1999, according to the paper. As many as 17,280 people infected with MRSA died in 2005, more than the number of people who died of AIDS that year. The paper, published in the December 2007 issue of the journal Emerging Infectious Diseases, stressed that MRSA should be “considered a national priority for disease control.”

These infections are caused by the bacterium Staphylococcus aureus, which usually lives on the skin and in the nasal passages and can be harmful if it enters the body through a sore or cut.

The growing number of MRSA cases reflects the increasing resistance of Staphylococcus bacteria to antibiotics over the last few years. The researchers discovered that resistance to various antibiotics like ampicillin and erythromycin increased by more than 20 percent between 1999 and 2005, and the researchers said the widespread use of antibiotics in the past few decades has made their use less effective.

Klein explained that the increase in MRSA cases has consequences beyond health risks. People who have infections resistant to treatment face a number of extra costs because they “tend to stay longer in hospitals and may need more expensive drugs,” he said. For instance, the cost of treating MRSA infections can range between $3,000 and $36,000 more than a methicillin-sensitive infection, according to his research.

Klein added that he believes there is a need to reduce the inappropriate use of antibiotics, which helps the bacteria develop their resistance. For example, instead of prescribing antibiotics to patients who are sick and insist on being prescribed drugs to “make them feel better,” doctors should explain to their patients when they don’t need antibiotics, Klein said.

“Every time somebody uses an antibiotic, that reduces the number of times the antibiotic can ever be used because it’s going to create resistance,” he explained.

Laxminarayan referred all requests for comment to Klein.

The researchers also discovered another important trend in their data. Hospital-associated MRSA infections, occurring mostly in patients with weakened immune systems, have been more common than community-associated MRSA infections, occurring among those who pick up the bacteria in fitness centers, common restrooms and other public places. The researchers found that the percentage of hospital outpatients who reported community-associated MRSA infections had jumped drastically from about 10 percent to roughly 50 percent between 1999 and 2005. They concluded that community-associated MRSA infections are currently spreading more rapidly, and that they are possibly making their way into hospitals.

To prevent transmission between people in the outpatient and inpatient units, Laxminarayan and Klein, in their paper, called for stringent hand-washing and other infection-control practices in hospitals.