In this study, researchers focused on microbes that are resistant to tetracycline. In addition to use in human medicine, tetracycline is an antibiotic that has been widely used for decades to promote growth in animals -- often in chicken, cattle and pig farming. It's also commonly sprayed on plants, including apple and pear trees, to prevent diseases such as fire blight, which can devastate crops. In the US, tetracycline has been used even on organic farms. In Norway, rules on antibiotic use in farming of any kind are much stricter.
The scientists compared the antibiotic-resistant genes in honey bee populations from Arizona and Norway. There were surprising geographic differences.
When the research team studied the antibiotic-resistant genes in the Arizona honey bee population, they found six different variants of this genetic resistance -- each variant is the product of a mutation within the gene. In the bee population in Norway, the team found only one adaptation.