Antibiotic-Associated Gut Microbiome Changes Reported Up to 4–8 Years

Prior antibiotic prescriptions were associated with current differences in gut microbiome composition in an adult Swedish cohort, with a recent study describing signals detectable as long as four to eight years after treatment. Investigators linked prior antibiotic dispensing records to a single, present-day gut microbiome sample to assess associations between past exposure and current microbial community patterns. The update also notes that these associations were not uniform across antibiotic types and were interpreted in the context of registry linkage and the microbiome sampling design.

Investigators linked Sweden’s prescribed drug register—capturing antibiotics dispensed at pharmacies—to gut microbiome data held in Swedish biobanks. The cohort comprised 14,979 adults living in Sweden whose prescription histories could be connected to detailed microbiome profiles. Microbiome sampling was performed once per participant, with comparisons described between those who had received different antibiotic types and those who had not received antibiotics during the relevant period. The article also notes that investigators are collecting a second sample from almost half of participants as follow-up.

Variation by antibiotic class was a prominent theme, with the strongest described associations tied to clindamycin, fluoroquinolones, and flucloxacillin. In contrast, penicillin V—identified as a commonly prescribed option for infections treated outside hospitals in Sweden—was linked to smaller changes characterized as short-lasting. The report presents these differences without a single uniform pattern across all exposures, emphasizing that links between prior prescriptions and current microbiome profiles differed substantially by drug type. Heterogeneity across exposures is part of what investigators highlighted when summarizing the population-level findings.

Investigators underscored uncertainty and follow-up needs around some class-specific observations, including that the flucloxacillin association was unexpected and wanted to see it confirmed in other studies. They said the study's findings “may help inform future recommendations on antibiotic use,” particularly when weighing two equally effective options that may differ in their impact on the gut microbiome. Follow-up sampling is underway, with the aim of better understanding recovery time after antibiotic treatment and identifying microbiomes that may be more susceptible to disruption. The next steps focus on additional sample collection intended to refine how duration and recovery are characterized in this cohort.