雅思阅读 120: One Course of Antibiotics Reshapes the Gut for Years

改编自 Scientific American 2026 年真实文章，去广告后按雅思阅读题型出题。

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Reading Passage

Antibiotics are designed to wipe out infection-causing bacteria. But even a single course can leave a lasting mark on the gut microbiome, according to a new study of nearly 15,000 adults in Sweden.

The research cross-referenced stool samples with Sweden's prescribed drug registry. It compared the gut microbiomes of people who had taken antibiotics at some point in the previous eight years with those who had not. The paper was published in Nature Medicine.

On average, people who had not taken antibiotics in eight years had about 350 unique bacterial species living in their gut. Those who had taken any antibiotics had fewer. The level of diversity also depended on which drug they had taken.

Clindamycin, sometimes prescribed for skin and dental infections, was the most disruptive. Each course taken in the year before stool sampling was linked to an average of 47 fewer detected species, as well as changes in abundance in almost 300 of the 1,340 species analyzed. Courses of fluoroquinolones, often prescribed for urinary tract and respiratory infections, and flucloxacillin, mainly used for Staphylococcus aureus infections, both corresponded to about 20 fewer species.

Previous research has linked lower gut diversity to obesity, type 2 diabetes and inflammatory bowel disease. But experts caution that high diversity alone is not the full picture. "High diversity is probably better," says Jotham Suez, a microbiome researcher at Johns Hopkins Bloomberg School of Public Health, "but there's not strong evidence."

In the study, the antibiotics' effects were strongest when taken in the year immediately before stool sampling. In general, the more courses people took, the larger the change in diversity. But even a single course taken up to eight years earlier had an effect. By comparison, penicillin V, one of the most commonly prescribed antibiotics in Sweden, was linked to changes in just 29 species.

Bacterial diversity recovered fastest in the first two years after antibiotics; the rate then tapered off. "It seems like you don't recover completely," says Tove Fall, a molecular epidemiologist at Uppsala University and the study's senior author.

Clindamycin and fluoroquinolones are broad-spectrum antibiotics that target a wide range of bacteria and reach high concentrations in the colon. This may explain their outsized effects. But flucloxacillin, a narrow-spectrum penicillin, was a surprise. Its effect might be related to its variable absorption and partial bile excretion, meaning more of it ends up in the large intestine.

Experts note the findings may not directly apply to the US population. In Sweden, where antibiotic use is less frequent, the microbiome may be more sensitive. Studies have linked antibiotic use to inflammatory bowel disease, cardiovascular disease and increased risk of Clostridioides difficile infection. Whether probiotics help recovery is debated. "There's just no evidence that probiotics are the answer," Suez says.

Fall hopes the data will be useful for policymakers but worries about misinterpretation. If people avoid necessary antibiotics because of these findings, "that could be a very bad consequence." Suez agrees: "Antibiotics are nothing less than a miracle drug."

Questions 1-5

Choose the correct letter, A, B, C or D.

1. How many adults were in the Swedish study?

   • A. About 1,500.
   • B. Nearly 15,000.
   • C. About 500.
   • D. Over 50,000.

2. Which antibiotic was the most disruptive?

   • A. Penicillin V.
   • B. Clindamycin.
   • C. Amoxicillin.
   • D. Tetracycline.

3. How many fewer species were linked to a single clindamycin course?

   • A. About 20.
   • B. About 47.
   • C. About 100.
   • D. About 350.

4. How long does gut bacteria recovery fastest?

   • A. The first two years.
   • B. The first month.
   • C. Five years.
   • D. Ten years.

5. What does Suez say about probiotics?

   • A. They fully restore the microbiome.
   • B. There is no evidence they help recovery.
   • C. They are better than antibiotics.
   • D. They work only in Sweden.

Questions 6-8

Do the following statements agree with the information given in the passage? Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

6. Penicillin V caused changes in almost 300 bacterial species.
7. Broad-spectrum antibiotics may reach high concentrations in the colon.
8. The researchers recommend people stop taking antibiotics when sick.

Questions 9-13

Complete the summary below. Choose ONE WORD ONLY from the passage for each answer.

The Swedish study found that even a single course of antibiotics can reduce gut bacterial diversity for years. Recovery is fastest in the first two years but may never be complete. Experts warn that these findings should not lead people to avoid necessary antibiotics.

Answers

1. B
2. B
3. B
4. A
5. B
6. FALSE
7. TRUE
8. FALSE
9. antibiotics
10. two
11. necessary

Key Vocabulary

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