Study: Antimicrobial-resistant MRSA revealed; may reverse infection decline

ATLANTA — A new resistant strain of methicillin-resistant staphylococcus aureus may be on the rise due to the frequent use of over-the-counter antibacterial ointments, according to a study to be published in the October issue of Emerging Infectious Diseases.

As reported by, Japanese researchers made the finding after testing 259 MRSA strains for susceptibility to bacitracin and neomycin, two of the antibacterial ingredients commonly found in such OTC ointments as Neosporin and Polysporin.

According to the report, resistance to bacitracin and neomycin was only found in USA300, a type of MRSA found in the United States. Because triple-antibiotic ointments are widely used in the United States, and rarely outside of the U.S., researchers determined that there may be a link.

The USA300 strain of MRSA still can be treated with vancomycin and other drugs, the report noted, but doctors in the United States should be aware the ointment therapy may not be effective in USA300 infections.

Before this report, all indicators have pointed to the decline of MRSA infections. In 2010, a Centers for Disease Control and Prevention study published in the Journal of the American Medical Association showed that invasive (life-threatening) MRSA infections in healthcare settings declined 28% from 2005 through 2008. In addition, the study showed a 17% drop in invasive MRSA infections that were diagnosed before hospital admissions in people with recent exposures to healthcare settings.

That study complemented data from the National Healthcare Safety Network that found rates of MRSA bloodstream infections occurring in hospitalized patients fell nearly 50% from 1997 to 2007.

"Taken together and with other reports such as the March 2011 'CDC Vital Signs' article, these studies provide evidence that rates of invasive MRSA infections in the United States are falling," the CDC noted on its MRSA website. "While MRSA remains an important public health problem and more remains to be done to further decrease risks of developing these infections, this decrease in healthcare-associated MRSA infections is encouraging."

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