Researchers in the United States have warned about the likelihood of new strains of methicillin-resistant Staphylococcus aureus (MRSA) emerging over the next fews years and the threats they pose.
MRSA is not only considered a growing problem among people, but among horses, with up to 5% of horses in the general population known to carry the bacteria. On some farms, the prevalence can exceed 50%.
Carrier horses may never have a problem with MRSA, but are more likely to develop an MRSA infection under certain conditions, and there is a risk they can transmit MRSA to other horses and people.
The latest US research has explored Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, caused primarily by a single strain - USA300.
"The USA300 group of strains appears to have extraordinary transmissibility and fitness," says Dr Frank DeLeo, based at the National Institute of Allergy and Infectious Diseases' Rocky Mountain Laboratories in Hamilton, Montana. "We anticipate that new USA300 derivatives will emerge within the next several years and that these strains will have a wide range of disease-causing potential."
CA-MRSA is considered an emerging public health concern. It typically causes readily treatable soft-tissue infections such as boils, but also can lead to life-threatening conditions that are difficult to treat.
Two studies have been conducted into CA-MRSA. One resolves debate about the evolution of CA-MRSA in the United States, ruling out the previously held possibility that multiple strains of USA300 - the most troublesome type of CA-MRSA in the United States - emerged randomly with similar characteristics.
A second study by the same scientists reveals new information about how MRSA bacteria in general, including the USA300 group, elude the human immune system.
The first study, which appears online this week in the Proceedings of the National Academy of Sciences, found that the USA300 group of CA-MRSA strains, collectively called the epidemic strain, comprises nearly identical clones that have emerged from a single bacterial strain.
"Scientists are pressing ahead quickly to learn more about how some MRSA strains evade the immune system and spread rapidly, says NIAID Director Anthony Fauci, MD. "The information presented in these two studies adds important new insights to that expanding knowledge base."
It is hoped that the work will lead to the development of new diagnostic tests that can quickly identify specific strains of MRSA.
The second report was recently published online in the Journal of Immunology.
The National Institute of Allergy and Infectious Diseases is part of the National Institutes of Health, which includes 27 institutes and centres, and is under the US Department of Health and Human Services.
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