Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

MRSA toxin acquitted: Study clears suspected key to severe bacterial illness

08.11.2006
Researchers who thought they had identified the bacterial perpetrator of the often severe disease caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) had better keep looking: Scientists at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, have exonerated a toxin widely thought to be the guilty party.

Panton-Valentine leukocidin (PVL) is one of many toxins associated with S. aureus infection. Because it can be found in virtually all CA-MRSA strains that cause soft-tissue infections, several research groups previously have proposed that PVL is the key virulence factor.

But new evidence strongly suggests that is not the case. A study led by NIAID researchers at Rocky Mountain Laboratories (RML) in Hamilton, MT, shows that the two major epidemic CA-MRSA strains and the same strains with PVL removed are equally effective at destroying human white blood cells--our primary defense against bacterial infections--and spreading disease. The findings, which appear online in The Journal of Infectious Diseases, are surprising because many scientists had presumed that CA-MRSA uses PVL to target and kill specific white blood cells known as neutrophils.

"The Staphylococcus aureus bacterium is a growing global public health menace because of its rapid spread from hospital settings into communities of healthy people," says NIAID Director Anthony S. Fauci, M.D. "This is an evolving pathogen that in recent decades has developed resistance to common medical treatments and now is finding new mechanisms to spread and cause severe illness."

About 75 percent of CA-MRSA infections are localized to skin and soft tissue and usually can be treated effectively. CA-MRSA strains have enhanced virulence, meaning they can infect otherwise healthy people. One of the biggest problems with CA-MRSA skin infections is that they spread rapidly and have the potential to cause illness much more severe than traditional hospital-associated MRSA infections, where PVL is less common. These life-threatening infections can affect vital organs and lead to widespread infection (sepsis), toxic shock syndrome and flesh-eating pneumonia. It is not known why some healthy people develop CA-MRSA skin infections that are treatable whereas others infected with the same strain develop severe infections or die.

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 questioning whether PVL truly led to severe illness, says Barry Kreiswirth, Ph.D., study co-author and a leading staphylococcal epidemiologist from ICPH in Newark. He adds, "We routinely receive calls from clinical microbiology laboratories asking to test for the presence of PVL, and it is hard to dissuade them that the PVL results will not affect patient care. Hopefully, the robust and contrary findings in our study provide the experimental evidence to convince the staphylococcal researchers and clinicians that PVL is not a significant virulence factor."

Next, Dr. DeLeo says his group will shift away from PVL and try to determine exactly which toxin or other mechanism in S. aureus kills white blood cells and allows the spread of CA-MRSA infection.

Ken Pekoc | EurekAlert!
Further information:
http://www.niaid.nih.gov

More articles from Studies and Analyses:

nachricht Multi-year study finds 'hotspots' of ammonia over world's major agricultural areas
17.03.2017 | University of Maryland

nachricht Diabetes Drug May Improve Bone Fat-induced Defects of Fracture Healing
17.03.2017 | Deutsches Institut für Ernährungsforschung Potsdam-Rehbrücke

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>