Navigation Links
Key Mechanism to Emergence of Strep Bacteria

Researchers at the University of California, San Diego (UCSD) School of Medicine and the University of Wollongong in Australia have discovered that, 30 years ago, a virus infected the strep bacteria creating a deadly strain of flesh-eating bacteria that has evolved to produce serious human infections worldwide.

The incidence of serious strep infections has risen dramatically in the last three decades, and this increase is largely attributed to the spread around the globe of a single strain of strep known as the invasive M1T1 clone.

Just like a computer virus might come in and reprogram your hard drive, this virus reprogrammed the genetic machinery of the M1T1 strep into a more virulent form, said senior author Victor Nizet, M.D., UCSD Professor of Pediatrics and Pharmacy.

The consequences of this event on human health are still being felt three decades later.The research, reported in the July 15 advance online publication of the journal Nature Medicine, focuses on the major human pathogen group A Streptococcus (strep.)

Among the most important of all human infectious disease agents, strep is responsible for a wide range of diseases, ranging from simple throat and skin infections to life-threatening invasive conditions such as necrotizing fasciitis (flesh-eating disease) and toxic shock syndrome.

Strep is estimated to cause over 700 million infections each year; over 650,000 of these are dangerous invasive forms.

The UCSD-Australian research team sought to identify what special characteristics make the invasive M1T1 strep clone so virulent for humans. They observed that during the early stages of a simple skin infection, a small subpopulation of the strep bacteria hijack a protein called plasminogen from the human bloodstream.

The bacteria attach the protein to their own surface, and then activate it into a protease an enzyme that digests proteins and is capable of destroyin g cells and tissues thus allowing the bacteria to break out and spread through the body.

Applying the pressure of natural selection, the human immune system normally would clear a localized infection. But in the case of the M1T1 strep clone, natural selection instead favors the emergence of the invasive mutants.

The researchers found that a specific genetic mutation in the M1T1 strep clone controls the shift to this invasive form a property which they traced to an event that occurred about 30 years ago when a virus known as a bacteriophage infected the strep bacteria and introduced a new gene. The new gene allowed the bacteria to resist clearance by the human immune system.

Our study provides a model of how natural selection, exerted by the human immune system, can generate hypervirulent bacterial variants with an increased risk of producing invasive infections, said lead author Mark Walker, Ph.D. a Professor of Biological Sciences at the University of Wollongong.

In the case of the invasive strep clone, a bacteriophage provided the bacterium a genetic advantage that turned a relatively benign pathogen into a potential deadly disease agent.

A gene present on the bacteriophage acquired by the M1T1 strep encodes an enzyme that allows the bacteria to escape being trapped and killed by neutrophils white blood cells that play a front line role in humans immune defense by pathogenic microbes.

The same genetic mutation that allows the strep bacteria to acquire plasminogen and activate it throughout the body also increases production of the bacteriophage-encoded enzyme that blocks neutrophil killing.

When neutrophils of the immune system are summoned to clear a simple strep infection, they apply a natural selective pressure favoring the genetic mutation.

The mutation allows the bacteria not only to survive neutrophil killing, but to spread and destroy tissues, as is seen in necrotizing fasciitis and other severe forms of strep infection, said Walker.

The research team used genetically engineered mice expressing human plasminogen and infected them with M1T1 strep clone, discovering that the bacteria routinely mutated to the invasive form, then spread throughout the body to produce a fatal infection.

When the researchers eliminated the single bacteriophage gene encoding the neutrophil resistance factor, the M1T1 strep strain lost its ability to undergo the dangerous mutation and could no longer spread to produce severe infection.

Ancestral strains of the M1T1 strep, isolated before the acquisition of the bacteriophage, also failed to undergo the mutation to produce serious disease.


Related medicine news :

1. Scientists Unveil Mechanism Behind Resistance to Severe Malaria
2. New Gene Silencing Mechanism To Prevent Cancer
3. Molecular Mechanism Of HIV Infecting The Healthy Cells Discovered.
4. Self-defense Mechanism of food borne bugs found
5. Specific Immune Mechanism against DNA viruses
6. A New Focus For The Mechanism Of Nerve Growth
7. Mechanism of Stem Cell Regulation Identified
8. Cancer-Killing Viruses Employ Multiple Mechanisms
9. Regulatory Mechanism for Tumor Suppressor Protein Identified
10. Study Identifies Mechanism Which May Help Tamoxifen Work Better
11. Genetic Mechanism Helps Explain Chronic Pain Disorders
Post Your Comments:

(Date:11/25/2015)... (PRWEB) , ... November 25, 2015 , ... ... offering factory direct sauna parts and accessories. , Sauna accessories help improve ... the bather’s style and personality. From basic styles for the purist looking for ...
(Date:11/25/2015)... ... November 25, 2015 , ... On November 10, 2015, ... District Court of Connecticut on behalf of a home health care worker who provided ... or former home health care workers employed by Humana, Inc., Humana at Home, Inc., ...
(Date:11/25/2015)... ... November 25, 2015 , ... ... across the country to celebrate their sobriety and show through pictures what a ... and after” photos this Thanksgiving with the hashtag #FacesOfGratitude on their Facebook, Twitter, ...
(Date:11/25/2015)... ... November 25, 2015 , ... Wimbledon Health ... launches new Wimbledon Athletics Facebook page to educate the public, parents ... cardiac abnormalities. About 2,000 people under the age of 25 die from sudden ...
(Date:11/25/2015)... ... November 25, 2015 , ... Smiles by Stevens is ... and moderate facial wrinkling. While many patients are aware of the benefits of Botox® ... Botox® delivers to those suffering with discomfort, soreness, and pain as a result of ...
Breaking Medicine News(10 mins):
(Date:11/26/2015)... DUBLIN , November 26, 2015 ... has announced the addition of the  ... in the European Cell Surface Marker ... Emerging Opportunities"  report to their offering.  ... announced the addition of the  "2016 ...
(Date:11/25/2015)...  Amgen (NASDAQ: AMGN ) today announced the ... the United States (U.S.) Food and ... to Humira ® (adalimumab). Amgen believes this submission ... FDA and represents Amgen,s first BLA submission using the ... M.D., executive vice president of Research and Development at ...
(Date:11/25/2015)... 25, 2015 AAIPharma Services Corp./Cambridge Major ... at least $15.8  Million to expand its laboratories ... . The expansion will provide additional office ... growing demands of the pharmaceutical and biotechnology markets. ... will provide up to 40,000 square feet of ...
Breaking Medicine Technology: