Tuesday, March 22, 2016

Antibiotic Resistance: It's a Social Thing

Date: March 15, 2016
Source: University of York
Summary: Trace concentrations of antibiotic, such as those found in sewage outfalls, are enough to enable bacteria to keep antibiotic resistance, new research has found. The concentrations are much lower than previously anticipated, and help to explain why antibiotic resistance is so persistent in the environment.


Aerial view of sewage water treatment plant.
Credit: © josefkubes / Fotolia

Trace concentrations of antibiotic, such as those found in sewage outfalls, are enough to enable bacteria to keep antibiotic resistance, new research from the University of York has found. The concentrations are much lower than previously anticipated, and help to explain why antibiotic resistance is so persistent in the environment.

Antibiotic resistance can work in different ways. The research described the different mechanisms of resistance as either selfish or co-operative. A selfish drug resistance only benefits the individual cell with the resistance while a co-operative antibiotic resistance benefits both the resistant cell and surrounding cells whether they are resistant or not.

The researchers analysed a plasmid called RK2 in Escherichia coli, a bacterium which can cause infectious diarrhea. RK2 encodes both co-operative resistance to the antibiotic ampicillin and selfish resistance to another antibiotic, tetracycline. They found that selfish drug resistance is selected for at concentrations of antibiotic around 100-fold lower than would be expected -- equivalent to the residues of antibiotics found in contaminated sewage outfalls.

The study, which is published in Antimicrobial Agents and Chemotherapy (AAC), involved Professor Michael Brockhurst, Dr Jamie Wood and PhD student Michael Bottery in the Departments of Biology and Mathematics at York. The work was supported by the European Research Council under the EU's Seventh Framework Programme and the Wellcome Trust.

Dr Wood said: "The most common way bacteria become resistant to antibiotics is through horizontal gene transfer. Small bits of DNA, called plasmids, contain the resistance and can hop from one bacteria to another. Worse still, plasmids often contain more than one resistance."

Michael Bottery added: "There is a reservoir of antibiotic resistance out there which bacteria can pick and choose from. What we have found is some of that resistance can exist at much lower concentrations of antibiotic than previously understood."

Source: University of York. "Antibiotic resistance: it's a social thing." ScienceDaily. ScienceDaily, 15 March 2016. .

Friday, March 11, 2016

New Report: Attribution of Extreme Weather Events in the Context of Climate Change

A new report from the National Academies of Sciences, Engineering, and Medicine concludes it is now possible to estimate the influence of climate change on some types of extreme events. Confidence is strongest in attributing types of extreme events that are influenced by climate change through a well-understood physical mechanism, such as, the more frequent heat waves that are closely connected to human-caused global temperature increases, the report finds. Confidence is lower for other types of events, such as hurricanes, whose relationship to climate change is more complex and less understood at present. For any extreme event, the results of attribution studies hinge on how questions about the event’s causes are posed, and on the data, modeling approaches, and statistical tools chosen for the analysis. Read a 4-page summary of the report's findings and download the report for free.