FunNature & AnimalBrown bears become resistant to antibiotics

Brown bears become resistant to antibiotics

Antibiotic resistance has been a real and growing problem for decades. The brown bears in the forests of Sweden are also suffering from it, even those who have no contact with humans.

A team of researchers led by microbiologist Jaelle Brealey from the Norwegian University of Science and Technology wanted to investigate how antibiotics penetrate the environment . These and bacteria resistant to them are known to end up in the wild through sewage. Its consequences on aquatic animals have also been examined. However, understanding its impact more broadly is a more difficult task.

Scientists set about studying brown bear skulls in a museum dated between 1842 and 2016, more specifically examining their teeth . The idea was to obtain samples of dental calculus, a form of plaque that preserves samples of the communities of bacteria in the mouth. The team sequenced these bacterial genomes, looking for antibiotic resistance genes.

They found increasing levels of these bacteria in the teeth of bears beginning in the 1950s . This was followed by a decline after the Swedish government banned the use of antibiotics in agriculture in the 1980s, and later implemented a program to combat antibiotic resistance in 1995.

The abundance [of bacteria] closely follows the use of antibiotics by humans in Sweden , increasing in the 20th century and decreasing in the last 20 years,” Brealey said. “We also found a greater diversity of antibiotic resistance genes in the recent past , probably as a result of the different types of antibiotics used by humans.”

The analyzed bears came from different regions of Sweden. The researchers thought that, depending on their proximity to humans, the teeth would have more or less resistance to antibiotics. The reality is that it was not. “We found similar levels of antibiotic resistance in bears in remote areas and in those close to human dwellings,” says geneticist Katerina Guschanski, from the University of Uppsala (Sweden) and the University of Edinburgh (Scotland). . “This suggests that contamination of the environment with resistant bacteria and antibiotics is really widespread.”

Bears born after 1995 show low levels of antibiotic resistant bacteria, which is encouraging. Those levels are not as low as before the introduction of antibiotic production on an industrial scale in the 1940s, but they reflect that we can act on the environmental problems we cause.

“Our case study suggests that human actions, both negative and positive, may have a direct impact on diverse microbial communities, including those associated with wild animals,” the researchers wrote, “and provides evidence that large-scale policies that limit antimicrobial use in humans and livestock may be effective in slowing the spread of antimicrobial resistance through environmentally mediated pathways. “

The research has been published in Current Biology .

 

Fuente: The oral microbiota of wild bears in Sweden reflects the history of antibiotic use by humans; Jaelle C. Brealey, Henrique G. Leitão, Thijs Hofstede, Daniela C. Kalthoff, Katerina Guschanski, August 25, 2021. DOI:https://doi.org/10.1016/j.cub.2021.08.010

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