Researchers, from the Washington University School of Medicine in St. Louis, noted that international travellers often return home with an unexpected bounty of new bacterial strains jostling for position among the thousands that normally reside within the gut microbiome.
"Even before the Covid-19 pandemic, we knew that international travel was contributing to the rapid global increase and spread of antimicrobial resistance," said Alaric D'Souza, an doctoral student at the varsity.
"But what's new here is that we've found numerous completely novel genes associated with antimicrobial resistance that suggest a worrisome problem on the horizon," D'Souza added. The findings are published in the journal Genome Medicine.
Poverty, poor sanitation and changing agricultural practices have turned many low-income, developing regions into hot spots for diseases spread by bacteria, including infections that are increasingly resistant to a range of antibiotic drug treatments.
For the study, the team analysed bacterial communities in the gut microbiomes of 190 Dutch adults before and after travel to one of four international regions where the prevalence of resistance genes is high: Southeastern Asia, South Asia, North Africa and Eastern Africa.
In all, the researchers detected 121 antimicrobial resistance genes across the gut microbiomes. More than 40 per cent of these resistance genes were only discovered using the more sensitive metagenomics technique, suggesting that potentially dangerous genes are being missed by the more conventional approaches.
The results also confirmed that 56 unique antimicrobial resistance genes had become part of the travellers' gut microbiomes during their trips abroad, including several mobile, high-risk resistance genes, such as extended-spectrum beta-lactamases (ESBL) and the plasmid-borne colistin resistance gene, mcr-1.
The rapid spread of antimicrobial resistance is one of the most serious public health threats now facing the world -- a looming medical catastrophe that could outweigh the chaos created by the Covid-19 pandemic.
"Identifying new antimicrobial resistant bacteria and genes could play an important role in slowing the global spread of resistance and guide potential treatments for related diseases," Gautam Dantas, Professor of pathology and immunology at Washington University.