Whether pneumonia or sepsis – infectious diseases are becoming increasingly difficult to treat.
One reason for this is the growing antibiotic resistance. But even non-resistant bacteria can survive antibiotics for some time, and that’s why treatments need to be continued for several days or weeks.
Scientists at the Biozentrum of the University of Basel showed that bacteria with vastly different antibiotic sensitivity coexist within the same tissue. In the scientific journal Cell they report that, in particular, slowly growing pathogens hamper treatment.
Many bacteria are principally susceptible to treatment, but can still survive for some hours to days in adverse environmental conditions, such as exposure to antibiotics. It is commonly assumed that these pathogens are in a type of “dormancy” state.
They don’t grow and thus become invulnerable against the effects of many antibiotics. However, Prof. Dirk Bumann and his team at the University of Basel's Biozentrum, demonstrated that dormant pathogens play only a minor role in Salmonella-infected tissue. Instead, abundant slowly growing bacteria are the biggest challenge for treatment.
Salmonella grows at different rates
Genetically identical bacteria can grow at very different rates, even within the same test tube. Is this also true for pathogens in infected host tissues? Bumann used a new method based on fluorescent colors, to measure the proliferation of individual Salmonella. The results revealed that in host tissues some Salmonella grow very rapidly, producing many daughter cells, which cause increasingly severe disease. Most bacteria, however, reside in tissue regions with limited nutrient supply, in which they grow only slowly.
Slow growth ensures survival
How do these diverse growth rates impact on the success of antibiotic therapy? Therapy of infected mice quickly ameliorated disease signs, but even after five days of treatment, some bacteria still survived in the tissues, posing a risk for relapse. “We could kill already 90 percent of the Salmonella with the first antibiotic dose, particularly those that grew rapidly”, reports Bumann, “but non-growing Salmonella survived much better. Treatment success thus depended on the Salmonella replication rate.”
This observation could support the current research focus on “dormant” bacteria. However, Bumann was surprised that such bacteria were actually not the biggest challenge for treatment. “Instead, slowly growing Salmonella are more important. They tolerate antibiotics less well compared to dormant bacteria, but they are present in much larger numbers, and readily restart their growth once antibiotic levels in the tissue drop, thus driving infection and relapse.
As a result, slowly growing pathogens dominate throughout the entire therapy. A better understanding of bacterial physiology of such slowly growing bacteria, could help us to shorten the duration of treatment with a more specifically targeted antibiotic therapy.” This is particularly interesting for infectious diseases that currently require medication over several weeks or even months, to prevent a recurrence of the infection.
Beatrice Claudi, Petra Spröte, Anna Chirkova, Nicolas Personnic, Janine Zankl, Nura Schürmann, Alexander Schmidt, and Dirk Bumann
Phenotypic variation of Salmonella in host tissue delays eradication by antibiotic chemotherapy
Cell, published 14 August 2014
Katrin Bühler | Universität Basel
First time-lapse footage of cell activity during limb regeneration
25.10.2016 | eLife
Phenotype at the push of a button
25.10.2016 | Institut für Pflanzenbiochemie
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
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...
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...
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...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
25.10.2016 | Earth Sciences
25.10.2016 | Power and Electrical Engineering
25.10.2016 | Process Engineering