Taking antibiotics can affect the composition of the gut’s bacterial community – the gut microbiome– for quite a long time but, According to a new study, the impact of some of these drugs can last up to eight years.
The research, led by scientists from Uppsala University (Sweden) and published this Wednesday in Nature Medicine, is based on the analysis of the microbiome of 15,000 people; some had taken antibiotics and others had not in the last eight years.
Although antibiotics protect against serious infections, overuse increases the risk of some conditions, such as type 2 diabetes and gastrointestinal infections. Scientists think that changes in the microbiome caused by these drugs could be behind these pathologies.
But while antibiotics are known to have a large short-term impact on the microbiome, the longer-term effect has barely been studied.
To find out, the team analyzed the gut microbiome of 14,979 residents in Sweden and compared that of participants who had taken different types of antibiotics in the past eight years and those who had not.
The analyzes discovered strong links between antibiotic use and the composition of each person’s gut microbiome – including the diversity of bacterial species.
“We can see that the use of antibiotics 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, first author of the study and former doctoral student at Uppsala University.
The study was made possible by Sweden’s comprehensive prescription drug registry, which contains information on all antibiotics dispensed in pharmacies: “Antibiotic use is taken very seriously in Sweden, and the country already has strict antibiotic management in place,” he says.
Not all antibiotics are the same
The study found that the results differed substantially depending on the type of antibiotic used.
The strongest associations were seen with clindamycin, fluoroquinolones and flucloxacillin, while penicillin V – the most prescribed antibiotic for treating infections outside of hospitals in Sweden – was associated with small, short-lived changes in the microbiome.
“The strong link between narrow-spectrum flucloxacillin and the gut microbiome was unexpected, and we would like to see this finding confirmed in other studies,” says Tove Fall, professor of Molecular Epidemiology at Uppsala University and principal investigator of the study.
Fall believes the study’s findings can 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.”
Since the study only looked at prescriptions from the past eight years, scientists believe doing a study with a longer follow-up period could provide more information.
Additionally, the gut microbiome was sampled only once per participant, so the team is currently collecting a second sample from nearly half of the participants.
“This will allow us to gain an even better understanding of recovery time and identify which gut microbiomes are most susceptible to alteration following antibiotic treatment,” concludes Fall.