Longitudinal fluctuations of common antimicrobial resistance genes in the gut microbiomes of healthy Dutch individuals

The human gut microbiome is an important reservoir of antimicrobial resistance genes (ARGs), collec-tively termed the 'resistome'. To date, few studies have examined the dynamics of the human gut resis-tome in healthy individuals. Previously, the authors observed high rates of ARG acquisition and significant abundance shifts during international travel. In order to provide insight into commonly occurring dynam-ics, this study investigated longitudinal fluctuations in prevalent ARGs (cfxA, tetM and ermB) in the resis-tomes of non-travelling healthy volunteers. In addition, this study assessed the prevalence of acquirable ARGs (blaCTX-M, qnrB, qnrS, vanA and vanB) over time. Faecal samples from 23 participants were collected at baseline and after 2 and 4 weeks. DNA was isolated, and ARG quantification was performed by quan-titative polymerase chain reaction adjusting for the total amount of bacterial 16S rDNA. vanA and qnrS were not detected in any of the samples, while the prevalence rates of vanB of non-enterococcal origin and qnrB were 73.9% and 5.7%, respectively. The ss-lactamase encoding blaCTX-M was detected in 17.4% of healthy participants. The results were compared with previous data from 122 travellers. ARG acquisitions observed in travellers were rare in non-travelling individuals during 4 weeks of follow-up, supporting the hypothesis of ARG acquisition during international travel. However, median -1.04-to 1.04-fold abun-dance changes were observed for 100% of cfxA, tetM and ermB, which did not differ from those found in travellers. Thus, common abundance shifts in prevalent ARGs of the gut resistome were found to occur independent of travel behaviour.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )