Corporate Banner
Satellite Banner
Scientific Community
Become a Member | Sign in
Home>News>This Article

Staphylococcus aureus Bacteria Turns Immune System Against Itself

Published: Thursday, December 05, 2013
Last Updated: Wednesday, December 04, 2013
Bookmark and Share
Scientists use primary human immune defense mechanism to destroy white blood cells.

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, professor and chair of microbiology and senior author of the paper.

Neutrophils, a type of white blood cell that ensnares invaders in neutrophil extracellular traps (NETs), a web-like structure of DNA and proteins, is one of the first lines of defense in the human immune response.

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 that 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 a goal requires a lot more study.”

Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,600+ scientific posters on ePosters
  • More than 3,800+ scientific videos on LabTube
  • 35 community eNewsletters

Sign In

Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Gut Bacteria that Protect Against Food Allergies Identified
Common gut bacteria prevent sensitization to allergens in a mouse model for peanut allergy, paving the way for probiotic therapies to treat food allergies.
Wednesday, August 27, 2014
Staphylococcus Aureus Bacteria Turns Immune System Against Itself
Around 20 percent of all humans are persistently colonized with Staphylococcus aureus bacteria, including the antibiotic-resistant strain MRSA.
Friday, December 13, 2013
Manipulating the Microbiome Could help Manage Weight
UChicago researchers team was able to unravel some of the mechanisms that regulate this weight gain.
Thursday, August 30, 2012
Scientific News
Antibiotic Overuse Might be Why so Many People Have Allergies
The Centers for Disease Control and Prevention estimates that drug resistant bacteria cause 23,000 deaths and two million illnesses each year.
Molecular ‘Kiss Of Death’ Flags Pathogens For Destruction
Researchers have discovered that our bodies mark pathogen-containing vacuoles for destruction by using a molecule called ubiquitin, commonly known as the "kiss of death."
Opening the Door to Safer, More Precise Cancer Therapies
New method regulates when, and how strongly, cancer-killing therapeutic T cells are activated.
Vaccination On The Horizon For Severe Viral Infection Of The Brain
Researchers from the University of Zurich and the University Hospital Zurich reveal possible new treatment methods for a rare, usually fatal brain disease.
What Do Animal Viruses Have to Do with Human Health?
Simon Anthony studies animal infections to prevent outbreaks in people.
‘Immune Camouflage’ may Explain H7N9 Influenza Vaccine Failure
The study is published in Human Vaccines & Immunotherapeutics.
How Flu Viruses Gain The Ability To Spread
New study reveals the soft palate is a key site for evolution of airborne transmissibility.
New Cell Type May Help Explain Dangerous Food Allergies
Researchers have discovered a new cell type that appears to drive life-threatening food allergies and may help explain why some people get severe allergic reactions and others do not.
Scientists Create Immunity to Deadly Parasite by Manipulating Host’s Genes
Research suggests a novel approach to boosting immunity by removing the mechanism that allows pathogens to cause disease.
10 to 1: Bugs Win in NASA study
Bugs are winning out, and that's a good thing according to NASA's Human Research Program.

Skyscraper Banner
Go to LabTube
Go to eposters
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,600+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,800+ scientific videos