Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Staphylococcus aureus bacteria turns immune system against itself

Around 20 percent of all humans are persistently colonized with Staphylococcus aureus bacteria, a leading cause of skin infections and one of the major sources of hospital-acquired infections, including the antibiotic-resistant strain MRSA.

University of Chicago scientists have recently discovered one of the keys to the immense success of S. aureus—the ability to hijack a primary human immune defense mechanism and use it to destroy white blood cells. The study was published Nov 15 in Science.

"These bacteria have endowed themselves with weapons to not only anticipate every immune defense, but turn these immune defenses against the host as well," said Olaf Schneewind, MD, PhD, professor and chair of the Department of Microbiology at the University of Chicago and senior author of the paper.

One of the first lines of defense in the human immune response are neutrophils, a type of white blood cell that ensnares invaders in neutrophil extracellular traps (NETs), a web-like structure of DNA and proteins. Captured bacteria are then destroyed by amoeba-like white blood cells known as macrophages. However, S. aureus infection sites are often marked by an absence of macrophages, indicating the bacteria somehow defend themselves against the immune system.

To reveal how these bacteria circumvent the human immune response, Schneewind and his team screened a series of S. aureus possessing mutations that shut down genes thought to play a role in infection. They looked to see how these mutated bacteria behaved in live tissue, and identified two strains that were unable to avoid macrophage attack. When these mutations—to the staphylococcal nuclease (nuc) and adenosine synthase A (adsA) genes respectively—were reversed, infection sites were free of macrophages again.

Looking for a mechanism of action, the researchers grew S. aureus in a laboratory dish alongside neutrophils and macrophages. The white blood cells were healthy in this environment and could clear bacteria. But the addition of a chemical to stimulate NET formation triggered macrophage death. Realizing that a toxic product was being generated by S. aureus in response to NETs, the team used high performance liquid chromatography and mass spectrometry techniques to isolate the molecule.

They discovered that S. aureus were converting NETs into 2'-deoxyadenosine (dAdo), a molecule which is toxic to macrophages. This effectively turned NETs into a weapon against the immune system.

"Sooner or later almost every human gets some form of S. aureus infection. Our work describes for the first time the mechanism that these bacteria use to exclude macrophages from infected sites," Schneewind said. "Coupled with previously known mechanisms that suppress the adaptive immune response, the success of these organisms is almost guaranteed."

S. aureus bacteria are found on the skin or in the respiratory tracts of colonized humans and commonly cause skin infections in the form of abscesses or boils. Normally not dangerous, severe issues arise when the bacteria enter the bloodstream, where they can cause diseases such as sepsis and meningitis. Antibiotic-resistant strains, such as methicillin-resistant S. aureus (MRSA), are difficult to treat and have plagued healthcare systems around the world.

Schneewind and his team hope to leverage their findings toward therapies against S. aureus infections. But both genes and the dAdo molecule are closely related to important human physiological mechanisms, and Schneewind believes targeting these in bacteria, without harming human function, could be difficult.

"In theory you could build inhibitors of these bacterial enzymes or remove them," Schneewind said. "But these are untested waters and the pursuit of such goal requires a lot more study."

The study, "Staphylococcus aureus Degrades Neutrophil Extracellular Traps to Promote Immune Cell Death," was supported the National Institute of Allergy and Infectious Diseases and the American Heart Association. Additional authors include Vilasack Thammavongsa and Dominique M. Missiakas

Kevin Jiang | EurekAlert!
Further information:

More articles from Health and Medicine:

nachricht Resolving the mystery of preeclampsia
21.10.2016 | Universitätsklinikum Magdeburg

nachricht New potential cancer treatment using microwaves to target deep tumors
12.10.2016 | University of Texas at Arlington

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>