Single MRSA Bacteria Strain Causes Severe Infections

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Source: Methodist Hospital, Houston Released: Mon 21-Jan-2008, 17:00

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Single MRSA Bacteria Strain Causes Severe Infections Libraries

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MRSA, STAPH INFECTION, INFECTIOUS DISEASE, PNAS Contact Information

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Researchers have discovered that the most dangerous form of staph infection now

occurring in the United States originates from a single strain of bacteria, not

multiple strains as previously believed. These findings were published online

today in the Proceedings of the National Academy of Sciences (PNAS).

 

Newswise — Researchers have discovered that the most dangerous form of staph

infection now occurring in the United States originates from a single strain of

bacteria, not multiple strains as previously believed. These findings were

published online today in the Proceedings of the National Academy of Sciences

(PNAS).

 

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), an

emerging public health concern, causes soft-tissue infections such as boils as

well as life-threatening conditions that are difficult to treat. It is estimated

that almost 100,000 cases of MRSA occurred in the U.S. in 2005 and almost 20

percent resulted in death.

 

“Our study confirms that a single strain, called USA300, of CA-MRSA is

responsible for many of the devastating infections which have spread rapidly

across the U.S. in recent years ,” said James Musser, M.D., Ph.D., co-author of

the PNAS paper and co-director of The Methodist Hospital Research Institute in

Houston. Musser is also the director of the Center for Molecular and

Translational Human Infectious Disease Research Center at TMHRI.

The study, led by Frank R. DeLeo, Ph.D., at the National Institute of Allergy

and Infectious Disease’s Rocky Mountain Laboratories in Hamilton, MT. 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. It is the first time scientists have used large-scale

comparative genome sequencing to reveal the origins of epidemic CA-MRSA.

 

This discovery may lead to better tools to allow physicians to identify,

diagnose, and treat this disease that has spread with extraordinary speed across

the United States during the past five years.

 

About the study

 

To understand how CA-MRSA evolves in complexity and spreads geographically,

researchers sequenced the genomes of 10 patient samples of the USA300 bacterium

recovered from individuals treated for MRSA at different U.S. locations between

2002 and 2005. They then compared these genomes to each other and to a baseline

USA300 strain used in earlier studies. Eight of the 10 USA300 patient samples

were found to have nearly indistinguishable genomes, indicating they originated

from a common strain. The remaining two bacteria were related to the other

eight, but more distantly.

Of the eight nearly indistinguishable USA300 patient samples, two caused far

fewer deaths in laboratory mice than the others, highlighting an emerging view

that tiny genetic changes among evolving strains can profoundly affect disease

severity and the potential for drug resistance to develop.

 

Other study collaborators included Fred C. Tenover, Ph.D., of the Centers for

Disease Control and Prevention in Atlanta, and Barry N. Kreiswirth, Ph.D., of

the International Center for Public Health (ICPH) in Newark, NJ.

 

About The Methodist Hospital Research Institute

 

The Methodist Hospital Research Institute represents the cornerstone of The

Methodist Hospital’s strategic vision and its future as a top-ranked academic

medical center. The Research Institute’s mission is to translate quickly the

latest discoveries from the laboratory to a new standard of care for our

patients and the world. The Research Institute is a place where scientists from

diverse specialties and backgrounds can share ideas and work together. TMHRI has

over 250 investigators and staff, 500,000 square feet of modern research space

in service or under construction, and a full compliment of research resources

for our major research programs in cancer, cardiovascular disease, diabetes and

metabolic disease, infectious disease, neurosciences, and transplantation

biology.

 

For more information on The Methodist Hospital Research Institute, see our

website at http://www.methodistresearch.com or call 713-441-8679.

 

http://www.newswise.com/articles/view/537082/?sc=dwhn

 

Also see -

 

Update on antibiotic-resistant Staph aureus

 

Emergence of community-associated methicillin-resistant Staphylococcus aureus

USA300 genotype as a major cause of health care-associated blood stream

infections.

 

 

 

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