Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Trojan horses for hospital bugs

17.05.2016

Staphylococcus aureus usually is a formidable bacterial pathogen. Sometimes, however, weakened forms are found in the blood of patients. Researchers of the University of Würzburg have now identified one mutation responsible for that phenomenon.

Staphylococcus aureus is a bacterium that is frequently found on the human skin and in the nose where it usually behaves inconspicuously. However, once inside the body, it can have life-threatening consequences such as abscesses, sepsis, pneumonia or myocarditis.


Scanning electron micrograph of S.aureus (Photo: Janice Haney Carr, Centers for Disease Control and Prevention)

How the pathogen manages to perform its disastrous work is still largely in the dark despite intensive research. Scientists from the Universities of Oxford and Würzburg have now unravelled an equally puzzling phenomenon. They present their results in the latest issue of the scientific journal PNAS.

Close relatives with distinct differences

"Recent studies have shown that in some cases Staphylococcus strains in the blood of patients differ substantially from those found in the nose," explains Professor Thomas Rudel, Head of the Chair of Microbiology at the University of Würzburg and one of the study's main authors together with his colleague Dr. Martin Fraunholz. "That is astonishing, as both types of bacteria often are very closely related in genetic terms," says Rudel.

The key differences: These bacteria are much less capable of destroying human immune cells in the blood – compared to their nasal relatives. At the same time, this mutation still allows the bacteria to enter the bloodstream in great numbers, survive much longer, causing a so-called bacteremia.

Differences due to mutation in one gene

In their search for the factor responsible for this loss of dangerous properties, the researchers stumbled upon a specific gene, called rsp in scientific lingo. This gene encodes a transcription factor, i.e. a protein that plays a central role in reading genes and producing proteins.

"If the gene is mutated, the properties of the bacteria populating the nose change: their toxicity declines drastically. As a result, bacteria with rsp mutation are absorbed efficiently by the immune system's phagocytes, but they are destroyed after a certain delay only," Rudel further. Being mobile, these immune cells can spread throughout the human body like a Trojan horse, frequently with fatal consequences.

No comparable mutations were found in Staphylococcus strains of the skin. So the scientists draw the conclusion that the new properties are only advantageous when the bloodstream is infected, but not when the skin or other soft tissues are affected.

"Our findings back the suggestion that spontaneous mutations are to blame when the regulatory system based on the rsp transcription factor loses its function," Thomas Rudel sums up the key results of the study. In consequence, the mortality drops at the start of an infection and the modified bacteria can penetrate deeply into the tissues and cause severe diseases.

The scientists find this discovery particularly exciting for one reason: It shows that even slight changes to the bacteria's genetic make-up drastically change the pattern and course of the disease. These so-called mutations in the bacteria can even take place while populating humans.

Keyword "Staphylococcus aureus"

Staphylococcus aureus translates as "golden grape-cluster berry". The name is derived from the phenomenon that the cells tend to form grape-like clusters that appear golden in colour. According to present research, around 25 to 30 percent of all people are carriers of the pathogen. Usually, it does not cause any problems. The pathogen only starts to spread when the immune system is weakened or the bacteria enter the human body through wounds.

A special variant of these bacteria has achieved dubious fame in the past years: The type of "Methicillin-resistant Staphylococcus aureus" – short: MRSA – is spreading increasingly in hospitals and retirement homes. What makes the germ so treacherous: It is resistant to most antibiotics – even to the strongest drugs which are used when all other standard therapies have failed.

Natural mutations in a Staphylococcus aureus virulence regulator attenuate cytotoxicity but permit bacteremia and abscess formation. Proceedings of the National Academy of Sciences of the United States of America, www.pnas.org/cgi/doi/10.1073/pnas.1520255113

Contact

Prof. Dr. Thomas Rudel, Department of Microbiology, Phone: +49 931 31-84401, e-mail: Thomas.Rudel@biozentrum.uni-wuerzburg.de

Dr. Martin Fraunholz, Phone: +49 931 31-83242, martin.fraunholz@uni-wuerzburg.de

Gunnar Bartsch | Julius-Maximilians-Universität Würzburg
Further information:
http://www.uni-wuerzburg.de

More articles from Life Sciences:

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

nachricht CWRU researchers find a chemical solution to shrink digital data storage
22.06.2017 | Case Western Reserve University

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 satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>