Microbiologists compare these superbugs to travelers disguised in the microorganisms of international travelers: “Even before the COVID-19 pandemic, we knew that international travel was contributing to the global increase and spread of antimicrobial resistance,” explains lead author Alaric D’Souza, medical student at the University of Washington. “However, with this new research, we are identifying several completely new genes associated with antimicrobial resistance that point to a more worrisome public health problem.”

International travelers have reported an unexpected abundance of new bacterial strains

Many developing “cells” of infection that are increasingly resistant to antibiotics. In these countries, the population density favors the participation of this bacteria in the community and its transmission to travelers by exposure via contaminated water and/or food, or by contact with contaminated surfaces in toilets, restaurants, hotel rooms, and poorly disinfected public transportation. Back home, travelers can pass on this new bacteria to family, friends, and other contacts in the community.

studying: Here, researchers analyze bacterial communities of the gut microbiome from fecal samples from 190 Dutch participants in the Carriage Of Multi-Sistant Bacteria After Travel study, before and after a trip to one of the four international high prevalence regions. Resistance genes are high: Southeast Asia, South Asia, North Africa and East Africa.

The team used a combination of whole metagenomic sequencing and functional metagenomics to identify known and novel genes that code for antimicrobial resistance. There are more traditional genomic techniques that will search for distinct genetic signatures of individual pathogens. But these tests can only identify already known pathogens, while metagenomic sequencing can identify all the organisms present in a given sample: good bacteria, dangerous bacteria, and even new bacteria.

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This analysis identifies:

  • Travel-related significant increases, in the acquisition of resistance genes, and the abundance and diversity of endemic bacteria specific to the area visited;
  • 121 antimicrobial resistance genes. 51 of them were detected using the most sensitive metagenomic technique, indicating that some risk genes are not taken into account by traditional methods;
  • 56 unique antimicrobial resistance genes have been identified as having “invaded” the participants’ gut microbiome during their overseas trips: among these resistance genes, the researchers identified resistance genes to the antibiotics beta-lactam (β-lactam) and colistin.

Travel is a factor in the spread of resistance: These findings therefore support international movements as a factor and vector for the global spread of antimicrobial resistance genes. The authors point out that antimicrobial resistance is today considered a public health priority by the World Health Organization (WHO). Beta-lactam resistance, in particular, is increasing worldwide and conferring widespread resistance to treatment with penicillin and other important antibiotics. Same for colistin, a treatment of last resort for multidrug-resistant Gram-negative bacteria infection.

If colistin resistance spreads to bacteria that are resistant to other antibiotics,

These bacteria can cause totally incurable infections…

“Horizontal” Gene Transfer: While with repeated exposure to antibiotics, some bacteria can slowly develop antibiotic resistance, the sharing of resistance genes can occur more rapidly, between bacteria, by horizontal transfer. During this transfer, DNA extracts are transmitted from one bacterium to another. And because the genes that code for resistance to different classes of antibiotics are often found in these same motile segments, a single horizontal swap can convert previously antibiotic-sensitive bacteria into multiple or super-resistant bacteria. Moreover, scientists here identify an important association between specific resistance genes and these mobile genetic elements.

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Thus, this work brings not only new knowledge about antimicrobial resistance genes but also about the genetic mechanisms underlying this rapid involvement in the gut microbiomes of international travelers. Therefore, new strategies are necessary to counter the development of this travel-related resistance.

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