Antimicrobial resistance genes “stowaway” in gut microbiota during international travel

We all know that antibiotics save lives. We also know that the inappropriate and excessive use of antibiotics has been the main factor in the emergence of resistant pathogens.1 What we are beginning to understand is that the growth of international travel favors the acquisition of antibiotic resistance genes; but what remains unclear is the extent and magnitude of this phenomenon. A new study published in Genome Medicine addresses this subject. 

Created 28 October 2021
Updated 03 November 2021

About this article

Created 28 October 2021
Updated 03 November 2021

The WHO has organized World Antimicrobial Awareness Week every year since 2015: global awareness week to promote the proper use of antimicrobials. The goal? To raise awareness among health professionals and the general public about the proper use of antimicrobials to fight antibiotic resistance. The authors have contributed new knowledge on the mechanisms by which antimicrobial resistance is spreading across the globe. Low- and middle-income countries generally have higher rates of antibiotic resistance than high-income countries. Moreover, the ability of resistance genes to spread via travel is  (sidenote: Context Resistance gene’s prevalence in the endemic region, specific bacteria harboring the gene, and presence of mobile genetic elements in the vicinity of the gene that may promote its spread. ) -dependent. The researchers thus sought to evaluate whether international travel to countries with high levels of resistance to certain antibiotics can facilitate the dissemination of resistance genes to regions with lower rates.

International travel promotes acquisition of resistance genes  

To confirm this hypothesis, the researchers created a group of 190 Dutch travelers (average age: 50.7 years) from the COMBAT (Carriage Of Multiresistant Bacteria After Travel) cohort. The subjects were divided into four subgroups according to the high antibiotic resistance area they visited: Southeast Asia, South Asia, North Africa or East Africa. A fecal sample was collected from each participant immediately before and after their trip, with trips lasting from 1 week to 3 months. 

The team combined shotgun sequencing, functional metagenomics, and statistical modeling tools to finely analyze the subjects’ gut resistome. Comparing the samples taken before and after travel, they found an increase in the number of antibiotic resistance genes after travel. Furthermore, the acquisition of resistance genes was found to be higher in travelers returning from Southeast Asia than in those returning from other destinations.  

56 resistance genes acquired during travel 

The researchers detected the acquisition of 56 resistance genes (and the loss of 4 genes) during travel, with those encoding proteins responsible for antibiotic efflux and antibiotic target modification the most common. These included classic and well-known resistance genes [blaCTX-M family (β-lactam resistance gene), mcr-1 (colistin resistance gene), variants of tetX (tetracycline resistant gene), and qnr (fluoroquinolone resistance gene)], as well as genes previously unknown. The authors found that 6/56 acquired genes were associated with the destination, including 3/6 detected in travelers returning from Southeast Asia which were dfrA1 variants that confer resistance to trimethoprim. Furthermore, mobile genetic elements identified next to resistance genes may contribute to the high number of these genes acquired by subjects who traveled to Southeast Asia. 

Better understanding the mechanisms involved in the spread of antibiotic resistance: with this goal in mind the Biocodex Microbiota Foundation has recently launched its International Grant for 2022 on the research theme entitled “Structure and Function of the Gut Microbiota Resistome”. A collective and multidisciplinary effort is being made to counter antibiotic resistance. 

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