The mouth bacteria of wild bears in Sweden hold a historical record of human antibiotic use and the rise of antibiotic resistance.
Antibiotics are used widely in medicine and agriculture, and can leak into the environment via untreated waste water. Wild animals can then encounter contaminated water, soil or food sources, and play a role in the evolution of antibiotic resistance.
To track changes in antibiotic resistance over time,聽, then at Uppsala University in Sweden, and her colleagues sequenced the oral microbiomes of Swedish brown bears, using museum specimens dated from 1842 to 2016. They did this by extracting genetic material from the hardened tooth plaque of each bear. 鈥淭his is bacteria that we brush off every morning and every evening when we clean our teeth,鈥� says team member , also at Uppsala University, 鈥渂ut bears don鈥檛 have oral hygiene.鈥�
Advertisement
They found that the presence of antibiotic resistance genes in the bear samples closely mirrored records of human antibiotic use. An initial low level of natural antibiotic resistance nearly doubled after large-scale industrial production of antibiotics began in the 1940s. Brealey says the finding shows how much antibiotics have contaminated the natural world, 鈥渢o the point where we can see it in a wild animal that isn鈥檛 closely associated with humans鈥�.
The researchers also found a fall in the prevalence of resistance genes over the past 20 years, coinciding with Sweden implementing policies to mitigate antibiotic resistance. These policies included banning the use of antibiotics as growth promoters for farm animals, regulating the sale of antibiotics and launching awareness campaigns targeting both doctors and the general public.
鈥淗uman actions do have an impact on the environment, even in quite surprising ways,鈥� says Brealey. 鈥淎t the same time, good policy can actually somewhat reverse that effect.鈥�
Current Biology
