Antibiotic Resistance: Revelations on the Common, Life-Saving Drug

In addition to the growing epidemic of antibiotic resistance due to overuse, recent research has revealed that prescribing and taking just one round of antibiotics may have serious, long-lasting consequences to the human gut microbiome.

Just one week’s worth of antibiotics drastically changed patients’ gut microbiomes. Symptoms were sometimes observed up to a year. Since antibiotics are indiscriminate, both good and bad bacteria may be eradicated when taking antibiotics, which can lead to dysbiosis and inflammation.

The study, a randomized, placebo-controlled trial, utilized four commonly prescribed antibiotics, including clindamycin, ciprofloxacin, amoxicillin, and minocycline, as well as a placebo. Oral and gut microbiomes were then sequenced and analyzed prior to beginning the experiment, as well as one, two, four, and twelve months after.

Antibiotic Resistance and Consequences on the Microbiome

Which antibiotic the patient took made the effects vary drastically. The oral microbiome generally rebounded quickly, and the level of antibiotic-resistant genes associated were typically steady before and after treatment. However, the gut microbiome suffered significantly. Clindamycin and ciprofloxacin were correlated with a decrease in butyrate (a fatty acid that lowers gastrointestinal inflammation and stress)-producing bacteria. For patients prescribed clindamycin, symptoms lasted up to four months. Patients prescribed ciprofloxacin saw symptoms for at least 12 months. However, amoxicillin was not observed to have significant effects on the oral and gut microbiomes. Those prescribed minocycline had symptoms for less than one month.

Although many populations already carry antibiotic-resistant genes, researchers also revealed an increase in antibiotic-resistant genes after taking antibiotics.

It is obvious that just one round of antibiotics in otherwise healthy patients may increase the risk of developing antibiotic resistance and alter the gut microbiome negatively.


Zaura, E.,  Brandt, B.W., et al. (2015). Same Exposure but Two Radically Different Responses to Antibiotics: Resilience of the Salivary Microbiome versus Long-Term Microbial Shifts in Feces. mBio. <>

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