When antibiotics(抗生素)first became available, farmers used them freely. Now scientists know that the overuse of antibiotics can cultivate drug-resistant bacteria that are dangerous to human health. Among debates over what kinds of restrictions should be put in place, figuring out how antibiotic-resistant bacteria evolve and make their way to humans remains an area of intense interest.
Jo Handelsman is tracing one such pathway that, as she puts it, travels from "farm to table."Handelsman, a microbiologist who is now associate director for science at the White House Office of Science and Technology Policy, looked into dairy cows, which are often treated with antibiotics and produce manure(排泄物)that farmers use on their crops. In addition to nutrients, that fertilizer may harbor antibiotic-resistant bacteria—a problem because the bacteria can come into contact with plants that are finally shipped to supermarkets and sometimes eaten raw.
To find out how those antibiotic-resistant bacteria come to exist, Handelsman and her colleagues at Yale University added manure from a nearby Connecticut farm to raised beds of soil in 2013. In this case, the manure specifically came from cows that were not treated with antibiotics. The researchers unexpectedly found that there were more soil bacteria carrying antibiotic-resistant genes when they were grown with the manure than when they were grown with synthetic nitrogen-based fertilizer—even though the cows were drug-free.
Previous research has found that manure from pigs treated with antibiotics contains resistant bacteria, but the cow-pie results suggest there are more factors promoting resistance besides antibiotic use. Something about manure itself may encourage naturally resistant bacteria to increase.
The findings should not, however, give the impression that resistance is everywhere, notes Lance Price, a microbiologist at George Washington University(who was not involved in the study). "We can control this. There's very clear evidence that when we turn off the antibiotic tap, we bring down drug-resistant bacteria," says Lance.
Next on the farm-to-table schedule, Handelsman will test whether radishes grown in soil treated with cow manure are capable of taking up resistant genes from bacteria through their vascular system(循环系统). "They have veins(血管)just like us," she says. "We don't have any evidence yet that they're taking up the bacteria, but it's a really interesting possibility."
43. What does Jo Handelsman's research focus on?
A.How antibiotics makes its way onto our table. |
B.What restrictions should be put to antibiotics use. |
C.How antibiotics-resistant bacteria reach human beings. |
D.What damage the overuse of antibiotics does to humans. |
44. What did Jo's research find?
A.Drug-free cows produced manure with antibiotic-resistant bacteria. |
B.Synthetic nitrogen-based fertilizer did more good to the environment. |
C.Soil bacteria carrying antibiotic-resistant genes were increasing with time. |
D.Manure from pigs treated with antibiotics contained fewer resistant bacteria. |
45. Lance Price is quoted in the passage in order to ________.
A.provide more evidence that drug-resistance bacteria are dangerous |
B.suggest another possible explanation to the antibiotics problems |
C.emphasize the importance of feeding cows with no antibiotics |
D.show that the research findings may not be that worrisome |
46. Which of the following statements is Jo most likely to agree with?
A.It is very likely that widespread resistance to antibiotics is not inevitable. |
B.Plants grown in soil fertilized with cow manure may contain drug-resistant genes. |
C.There is possibility that radishes take up resistant genes wherever they are planted. |
D.The vascular system plays a key role in guarding radishes against bacteria. |