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Researchers have now collected a second sample from nearly half of the participants. The analyses are expected to reveal which effects remain after 16 years.
Photo Credit: Sandra Gunnarsson
Scientific Frontline: Extended "At a Glance" Summary: Long-Term Antibiotic Impact on the Gut Microbiome
The Core Concept: Antibiotic treatments can alter the composition and diversity of the bacterial community in the gastrointestinal tract, known as the gut microbiome, with measurable disruptions persisting for four to eight years after a single course of treatment.
Key Distinction/Mechanism: While the short-term disruptive effects of antibiotics on gut flora are well-documented, this research establishes the protracted nature of this ecological footprint. The mechanism of disruption varies significantly by antibiotic class; drugs such as clindamycin, fluoroquinolones, and the narrow-spectrum flucloxacillin cause substantial, long-lasting decreases in bacterial diversity, whereas commonly prescribed options like penicillin V result in only minor, transient changes.
Major Frameworks/Components:
- Epidemiological Data Linkage: The methodology relies on cross-referencing longitudinal, individual-level pharmacy dispensing data with large-scale biobank microbiome mapping (utilizing Swedish population-based cohorts like SCAPIS and SIMPLER).
- Bacterial Diversity Reduction: The core metric for microbiome health in the study is the quantifiable decrease in the diversity of bacterial species present in the gut following exposure to specific antimicrobials.
- Antibiotic Stratification: The framework evaluates post-treatment recovery times by differentiating the ecological impact based on the specific spectrum and chemical class of the antibiotic administered.
Branch of Science: Molecular Epidemiology, Microbiology, Gastroenterology, and Pharmacology.
Future Application: These findings are positioned to refine future clinical guidelines and antibiotic stewardship programs. By identifying the specific recovery times and vulnerabilities of the microbiome, clinicians can optimize prescription protocols by selecting equally effective antibiotics that leave a weaker, shorter-lasting ecological footprint on the patient's gut.
Why It Matters: Understanding the long-term microbiome alterations caused by antibiotics provides a crucial missing link for prior epidemiological observations that correlate high antibiotic use with an increased risk of chronic health conditions, such as type 2 diabetes and secondary gastrointestinal infections. It underscores the hidden, multi-year biological consequences of routine therapeutic interventions.
Antibiotic treatments can affect the composition of the community of bacteria living in the gut, known as the gut microbiome, for a long time. A new study shows that certain types of antibiotics can be linked to changes in the gut microbiome as long as four to eight years after treatment.
Antibiotics can be lifesaving in serious infections, but epidemiological studies have also indicated links between high antibiotic use and an increased risk of certain health conditions, such as type 2 diabetes and gastrointestinal infections. The reasons for these observations are not fully understood, but changes in the gut microbiome are thought to play a role. This has raised questions about the long-term footprint of antibiotics on the gut microbiome. It is well known that antibiotics have a major short-term impact on the gut microbiome, but how long these changes persist has been unclear until now.
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Gabriel Baldanzi, research Assistant at the Department of Medical Sciences, Uppsala University.
Photo Credit: Mikael Wallerstedt
Even a single course of treatment left traces
An international research team, led by scientists at Uppsala University, has now found strong links between a person’s history of antibiotic use and the composition of their gut microbiome, including the diversity of bacterial species.
“We can see that antibiotic use as far back as four to eight years ago is linked to the composition of a person’s gut microbiome today. Even a single course of treatment with certain types of antibiotics leaves traces,” says Gabriel Baldanzi, the first author of the study and a former doctoral student at Uppsala University.
“Antibiotic use is taken very seriously in Sweden, and country already have a strict antibiotic stewardship,” Baldanzi adds. “People should continue to follow their doctor’s recommendations. Having said that, our findings help shed light on other long-term consequences of antibiotics that are rarely considered.”
In the study, the researchers analysed drug register data alongside a detailed mapping of the gut microbiome of 14,979 adults living in Sweden. The gut microbiome was compared between participants who had received different types of antibiotics and those who had not received any at all during the period. The study was made possible by Sweden’s comprehensive prescribed drug register, which contains information on all antibiotics dispensed at pharmacies. The researchers were then able to link this data to Swedish biobanks at Uppsala and Lund University containing gut microbiome data.
Stronger association with certain types of antibiotics
The researchers found that the results differed substantially depending on the type of antibiotic used. The strongest associations were observed for clindamycin, fluoroquinolones, and flucloxacillin. By contrast, penicillin V, the most prescribed antibiotic for the treatment of infections outside hospitals in Sweden, was linked to small and short-lasting microbiome changes.
“The strong link between the narrow spectrum flucloxacillin and the gut microbiome was unexpected, and we would like to see this finding confirmed in other studies. However, we believe that the findings of our study may help inform future recommendations on antibiotic use, especially when choosing between two equally effective antibiotics, one of which has a weaker impact on the gut microbiome,” says Tove Fall, Professor of Molecular Epidemiology at Uppsala University and principal investigator of the study.
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Researchers found that the use of certain types of antibiotics led to a decrease in the diversity of bacteria in the gut microbiome.
Photo Credit: Sandra Gunnarsson.
New samples collected for follow-up
The researchers acknowledge that the study only covered prescriptions from the previous eight years and that a longer follow-up period could provide further insights. Another aspect is that the gut microbiome was sampled only once per participant.
“We are currently collecting a second sample from almost half of the participants,” says Fall. “This will enable us to gain an even better understanding of the recovery time and identify which gut microbiomes are more susceptible to disruption following antibiotic treatment.”
Published in journal: Nature Medicine
Authors: Gabriel Baldanzi, Anna Larsson, Sergi Sayols-Baixeras, Koen F. Dekkers, Ulf Hammar, Diem Nguyen, Tíscar Graells, Shafqat Ahmad, Camila Gazolla Volpiano, Guillaume Meric, Josef D. Järhult, Thomas Tängdén, Jonas F. Ludvigsson, Lars Lind, Johan Sundström, Karl Michaëlsson, Johan Ärnlöv, Beatrice Kennedy, Marju Orho-Melander, and Tove Fall
Source/Credit: Uppsala University | Sandra Gunnarsson
Reference Number: mcb031126_01