A new study has closely examined the regrowth in gut bacteria after major antibiotic interventions, revealing that while much of our microbiome does recover, some species could be permanently eradicated.

The research focused on 12 healthy male subjects, each of who was initially subjected to a four-day treatment comprising three strong antibiotics designed to almost completely eliminate most bacterial species living in their gut. The participants were then monitored for six months to analyze how the microbial flora in their gut recovered.

The initial results were somewhat positive, with most bacterial species reappearing after around one and half months, but not everything returned to normal. At the six-month point the researchers discovered that nine common species of bacteria had still not reappeared in most of the subjects. No conclusions have been made by the researchers to link the missing gut bacteria to specific health effects, but Oluf Pedersen, lead on the study, does suggest recurrent antibiotic use may confer permanent gut bacteria alterations over a person's lifetime.