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Germ warfare: Bacteria warn each other when antibiotics are ...


Germ warfare: Bacteria warn each other when antibiotics are coming

Scientists find that Pseudomonas aeruginosa 'talk to each other' to dodge certain drugs

Anne Gulland

Bacteria communicate by sending distress signals to each other, helping them to avoid certain antibiotics.
The finding could help researchers come up with new tools in the fight against antibiotic resistance since it shows how bacteria develop protective behaviours against certain drugs.
Researchers from the University of Notre Dame, in Indiana, and the University of Illinois looked at the bacterium Pseudomonas aeruginosa – which causes pneumonia, sepsis and other infections – and its response to the antibiotic tobramycin, a drug commonly used in clinical settings.
This month the Centres for Disease Control and Prevention in the US warned of “nightmare bacteria” – one of which was P. aeruginosa – spreading throughout the country. They reported 200 cases of unusual resistance in 2017, where infections did not respond to standard antibiotics.
Writing in the Journal of Biological Chemistry, the researchers noticed the bacteria produced two signals in response to tobramycin: one was a localised stress response while the other was a larger, community reaction.
The team mapped each response and found the localised distress signal was produced in small areas at high concentrations.
They also discovered the two responses communicated different messages.
Joshua Shrout, one of the authors and associate professor of biological sciences at the University of Notre Dame, said researchers understand the stress response but not the larger response.
“The stress response tells the bacteria to stay in place and go into a growth phase called biofilm where they don’t grow very much and can weather the storm [of the antibiotic],” he said.
Shrout said researchers already knew that bacteria are good at avoiding the full dose of the antibiotic, but the study suggests that bacterial community responses to antibiotics are much more orchestrated than was previously understood.
“Now we have determined there are multiple messages being sent out but we don’t understand very well what each of the messages are saying. We would like to determine what the specific responses are. Do we need a new drug or could we do something with an existing drug?”  
A growing concern
The researchers also looked at the bacteria’s response to another antibiotic, carbenicillin. The bacteria behaved differently, suggesting there is another reason they may develop resistance to this particular antibiotic.
Nydia Morales-Soto, lead author of the paper and senior research scientist in civil and environmental engineering and earth sciences at the University of Notre Dame in Indiana, said there was a general lack of understanding about how communities of bacteria respond to antibiotics.
“Most of what we know is from studies about stationary biofilm communities, whereas less is known about the process beforehand, when bacteria are colonising, spreading and growing.
“In this study our research team specifically reviewed the behaviour of bacteria during this period and what that may mean for antibiotic resistance,” she said.
– © The Daily Telegraph

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