Cases of MRSA are declining in the military, according to new figures, and while researchers are not exactly sure what is causing the drop, they say it mirrors "encouraging decreases" in the broader population.
Methicillin-resistant staphylococcus aureus bacteremia, or MRSA, is a contagious bacteria that can be harder to treat because it resists many common antibiotics, such as penicillin and amoxicillin. Typically, it causes skin infections, but it can be life-threatening.
"Staphylococcus aureus is a leading cause of infections in healthy people in the community, and the leading cause of hospital-associated infections in the U.S.," explained study co-author Dr. Murray Clinton of the Brooke Army Medical Center and the San Antonio Military Medical Center.
In the new study, published in the Journal of the American Medical Association on Tuesday, researchers looked at the rates of MRSA infections contracted in hospitals, and outside hospitals in 9 million active duty and non-active military personnel. Cases generally are considered "hospital-onset" if the infection culture is obtained soon after a hospital admission.
Overall, the researchers found the rates of community and hospital-onset MRSA decreased from 2005 to 2010. The proportion of outbreaks of skin and soft tissue infections stemming from MRSA also dropped, from a peak high of 62 percent in 2006 to 52 percent in 2010.
But Dr. Michael David, an assistant professor of infectious diseases at the University of Chicago Medical Center who was not involved with the research, cautioned that the findings required perspective: In the 1990s, MRSA simply was not a cause of skin infections. It shot up incredibly fast between 2000 and 2005, and appears to have since leveled off.
"The news here is that it's slowly declining as a percentage," David summarized. "But it's still more often than not a MRSA strain that causes the infection."
He explained that the cause for concern is treating the related skin infections. Before MRSA, doctors could easily use penicillin to treat infections, but that is no longer true and resistance may continue to develop.
For now, researchers do not have a firm grasp on what is driving the decline in MRSA cases.
"Further evaluations are needed to better understand why this is occurring, including the impact of infection control or other unknown factors," Clinton said. To curb MRSA infections, hospitals are taking steps like carefully cleaning rooms, and encouraging providers and patients to wash their hands.
But the authors write that there might also be broad shifts in the epidemiology of the infections.
Though the new study appears to be in line with findings among the civilian population -- a CDC report, also published in JAMA, found that life- threatening MRSA infections in hospitals dropped by nearly 30 percent between 2005 and 2008 -- there are major differences between the two groups. Many of the populations at higher risk for certain staph infections, including older men and women, are under-represented in military personnel. That population also has lower rates of intravenous drug use, and has free access to health care, eliminating some of the socioeconomic factors that can drive infection risk.
Indeed, experts caution that though the researach shows a trend in the right direction, MRSA is still a very real problem.
"These infections can be hard to treat, and there is no universal way to prevent staph infections, like a vaccine," warned Clinton.