by Roberto
Fig. 1. Absolute change in Shannon diversity associated with travel to the eight most common travel destinations in the study. All box plots denote the median, interquartile range, and 95% quantiles. Significance was tested by t tests (paired except for between-group comparisons). Source. Frontispiece: International Airline Route Map. Source
Whether it is to attend meetings, carry out collaborative research, visit family, or simply explore exotic locations, scientists tend to do a lot of international travel (myself very much included). And one thing we do not want to experience during or after such travel is any sort of intestinal malfunction. It's no surprise that we want to learn as much as possible regarding what to do and what not to do before and during travel. That's what attracted me to a recent paper describing a metagenomic analysis of the gut microbiome of a cohort of international travelers. In the study 267 individuals traveling from the U.S. to diverse regions around the world filled out an extensive survey and provided pre- and post-travel stool samples. This allowed the authors to analyze various changes associated with international travel – gut microbiome perturbations, changes in antibiotic resistance gene and strain dynamics – and how these correlated with travel destination and behavior. I was personally struck by the different degrees of gut microbiome perturbations depending on destination. Overall microbial diversity tended to decrease. However, travel to South America, on average, did not affect diversity. And going to Central America even appeared to increase diversity. Food for thought...
Because the investigators are interested in the microbes that represent a great threat in terms of antibiotic resistance, they first determined the dynamics of Enterobacterales that expressed resistance to extended spectrum b-lactams (ESBL), carbapenems or colistin. Here came the first surprise. Of the 267 subjects, 101 (that's 38%!) acquired one or several of these antibiotic resistant microbes. By far the most common acquisition was of ESBL resistant bacteria (99 or 101). Even more surprising (at least to me) was the fact that the ESBL resistant strains were almost invariably Escherichia coli.
Fig. 2. For each genus present in at least 10% of samples, the proportion of travelers with an observed decrease vs increase in relative abundance. Red labelled points denote genera with significant skew. Source
This finding stimulated the authors to investigate E. coli strain dynamics. Given the depth of their sequencing, they could resolve different strains from their metagenomic data. While about 40% of travelers had acquired ESBL resistant E. coli, nearly twice that many acquired new E. coli strains. Indeed, most travelers returned with more strains that they had left with, and the new strains were phylogenetically distinct. The authors then analyzed how this acquisition correlated with travel, host, and behavioral variables. Travel to South Asia increased the risk of acquisition. In contrast, typhoid vaccination before travel reduced the risk. Surprisingly, drinking of unfiltered tap water also reduced the risk!
One final note on their findings. Based on analyses of pre-travel stool samples, the authors did not find any microbiome risk factors to predict acquisition of antibiotic resistance genes or the incidence of traveler's diarrhea. In their words: "Our risk factor analysis suggests that efforts to reduce the rate of acquisition of antimicrobial-resistant organisms in travelers by altering behavior (e.g., promoting handwashing and avoiding unnecessary antibiotic use) might be more effective than interventions seeking to modulate the state of the pre-travel microbiome (e.g., probiotics)." Makes sense. But if you wish to eat yogurt pre-travel, I say go for it. I do not think it will hurt.
Do you want to comment on this post? We would be happy about it! Please comment on Mastodon, Bluesky, or on 𝕏 (formerly Twitter).
Comments