Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Flesh-eating bacteria escape body’s safety net


Researchers at the University of California, San Diego (UCSD) School of Medicine have discovered that so-called flesh-eating "Strep" bacteria use a specific enzyme to break free of the body’s immune system, a finding which could potentially lead to new treatments for serious infections in human patients.

The research, reported in the February 21, 2006 issue of the journal Current Biology, focuses on the major human pathogen group A Streptococcus. Among the most important of all bacterial pathogens, strep is responsible for a wide range of diseases – from simple throat and skin infections to life-threatening conditions such as necrotizing fasciitis ("flesh-eating disease") and toxic shock syndrome.

"These findings suggest a novel approach to treating serious Strep infections, such as flesh-eating disease, by assisting our body’s own defense system," said senior author Victor Nizet, M.D., UCSD associate professor of pediatrics and an infectious diseases physician at Children’s Hospital, San Diego.

The UCSD investigators examined the interaction of Strep bacteria with neutrophils, specialized white blood cells that play a front line role in human’s immune defense against pathogenic microbes. Recent research by European investigators had shown that neutrophils are particularly effective defenders because they release "nets" composed of DNA and toxic compounds to entrap and kill invading bacteria. In the current study, the UCSD scientists proved that disease-causing Strep release an enzyme that degrades these DNA nets, thereby allowing the organism to escape the neutrophil net and spread in body tissues.

The UCSD team used a molecular genetic approach for their studies, knocking out the gene encoding the DNA-degrading enzyme from a pathogenic Strep strain that was originally isolated from a patient suffering from necrotizing fasciitis.

"Deprived of this single enzyme, the mutant Strep strain was easily killed by human neutrophils", said lead author John Buchanan, Ph.D., research scientist in the UCSD department of pediatrics. "In addition, the mutant Strep bacteria no longer produced a spreading infection when injected into the skin of experimental mice."

The critical role of the DNA-degrading Strep enzyme was confirmed by cloning the corresponding gene into a normally non-pathogenic bacterial strain. Addition of the single gene allowed these bacteria to degrade DNA, escape neutrophil killing, and produce a spreading ulcer in the mouse infection model. Special fluorescent microscopy techniques were used to observe how the Strep enzyme dissolved the DNA nets and allowed bacteria to float away from the neutrophils.

"The experiments explain how this DNA-degrading enzyme contributes to the severe infections produced by certain strains of Strep bacteria, while simultaneously confirming just how important neutrophil DNA nets are to our normal immune defense," said Buchanan.

Recognizing the critical role played by the DNA-degrading enzyme in progression of Strep disease, the UCSD researchers examined whether it could represent a target for therapy. Mice experimentally infected with Strep were treated by injecting a chemical inhibitor of the DNA-degrading enzyme at the site of infection. A dramatic reduction in bacterial counts and tissue injury was observed following the inhibitor treatment, when compared to controls receiving a placebo.

Nizet explained that the researchers’ findings could lead to novel treatments for Strep-related diseases. "Instead of attempting to kill the bacteria directly with standard antibiotics, a treatment strategy to inhibit the Strep DNA-degrading enzyme could disarm the pathogen, making it susceptible to clearance by our normal immune defenses," he said.

Debra Kain | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Two decades of training students and experts in tracking infectious disease
27.11.2015 | Hochschule für Angewandte Wissenschaften Hamburg

nachricht Increased carbon dioxide enhances plankton growth, opposite of what was expected
27.11.2015 | Bigelow Laboratory for Ocean Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Climate study finds evidence of global shift in the 1980s

Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fuelled by anthropogenic warming and a volcanic eruption, according to new research published this week.

Scientists say that a major step change, or ‘regime shift’, in the Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from...

Im Focus: Innovative Photovoltaics – from the Lab to the Façade

Fraunhofer ISE Demonstrates New Cell and Module Technologies on its Outer Building Façade

The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...

Im Focus: Lactate for Brain Energy

Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.

In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...

Im Focus: Laser process simulation available as app for first time

In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.

Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...

Im Focus: Quantum Simulation: A Better Understanding of Magnetism

Heidelberg physicists use ultracold atoms to imitate the behaviour of electrons in a solid

Researchers at Heidelberg University have devised a new way to study the phenomenon of magnetism. Using ultracold atoms at near absolute zero, they prepared a...

All Focus news of the innovation-report >>>



Event News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

Gluten oder nicht Gluten? Überempfindlichkeit auf Weizen kann unterschiedliche Ursachen haben

17.11.2015 | Event News

Art Collection Deutsche Börse zeigt Ausstellung „Traces of Disorder“

21.10.2015 | Event News

Latest News

Siemens to supply 126 megawatts to onshore wind power plants in Scotland

27.11.2015 | Press release

Two decades of training students and experts in tracking infectious disease

27.11.2015 | Life Sciences

Coming to a monitor near you: A defect-free, molecule-thick film

27.11.2015 | Materials Sciences

More VideoLinks >>>