Scientists had recognized a connection between MRSA strains that contain PVL and the increased occurrence and severity of CA-MRSA disease, though no one had directly tested the role of PVL in CA-MRSA virulence. In striving to learn more about CA-MRSA, the RML scientists, with their colleagues at the International Center for Public Health (ICPH) in Newark, NJ, and the Université Claude Bernard in Lyon, France, decided to test the PVL virulence theory, thinking that if they could understand the role of this toxin in disease, they could more quickly diagnose serious cases and develop effective treatments.
In addition to observing the destruction of human white blood cells regardless of whether PVL was present, the researchers also used mouse models to learn that CA-MRSA strains are just as pathogenic with or without PVL present. These findings were seen in tests with mice that displayed skin and soft-tissue infection and bacterial sepsis.
"The strains were just as deadly with or without the PVL toxin," says lead investigator Frank DeLeo, Ph.D., of RML. "Unexpectedly, the average abscess volume in mice infected with strains absent the PVL was slightly greater than those containing the toxin. The strong association between PVL and CA-MRSA makes the toxin an excellent marker to track community strains, but the assumption that it is the major virulence determinant driving this epidemic is simply not true."
These findings are significant because some infectious disease physicians who treat MRSA patients had begun questio
Source:NIH/National Institute of Allergy and Infectious Diseases