The emergence of antibiotic resistance among dangerous pathogens is increasingly problematic worldwide. Researchers at Osaka University have followed Japanese travellers to find out how short trips to a developing country can lead to the spread of resistance to the antibiotic colistin.
Many strains of infectious bacteria have become multidrug-resistant and cannot be treated with common antibiotic therapies. While colistin can often be used to treat infections by multidrug-resistant bacteria, colistin resistance is also on the rise and represents an emerging global health threat, further limiting available treatments.
"Extended-spectrum, beta-lactamase (ESBL) producing bacteria are resistant to most first-line antibiotics," first author Tatsuya Nakayama explains.
"Colistin is typically used as a last-resort treatment when there are no other therapy options available," he says. "Unfortunately, we're seeing an increase in ESBL strains carrying the mcr-1 gene, which confers colistin resistance to bacteria. In our study, we were interested in tracking the genotype of bacteria carried by international travellers to understand how short-term travel can impact the prevalence of mcr-1."
The researchers followed 19 Japanese participants who travelled to Vietnam for less than 2 weeks. They collected faecal samples before and after each trip and used a mix of biochemical and genetic assays to identify bacteria carried by each of the travellers. The team found that short-term trips led to a significant increase in ESBL-producing bacteria: resistant strains were found in nearly 90% of travel events, and in the majority of cases travellers had shown no sign of ESBL bacteria prior to their journey.
More concerning, however, was the researchers' finding that the mcr-1 gene – which absent among all travellers before leaving Japan – was carried back to Japan by three of the returning travellers during three separate travel events. The mcr-1 gene is carried on plasmid, a mobile DNA molecule that can readily jump from one strain of bacteria to another, which means even an isolated case of colistin resistance can quickly spread through a human population. The findings of the study thus suggest that even a relatively short international trip has the potential to serve as a starting point for the spread of colistin resistance.
"Our study supports the notion that even short-term travel can bring colistin-resistant strains back to the country of origin," senior author Yoshimasa Yamamoto concludes
"In a globalised community in which travel to developing countries is common, the spread of colistin-resistant bacteria is a significant concern to worldwide health. We need to ensure that proper surveillance and public hygiene measures are in place, so that we can minimise the dissemination of highly resistant strains to the greatest extent possible."
Abstract
Background: Due to increasing colistin usage, the dissemination of the colistin-resistant gene mcr-1 has been increasingly investigated. The aim of this study was to determine whether a traveler on a short-term international trip to a developing country could bring mcr-1 back to their home country.
Materials and methods: Thirty-four travel events from Japan to Vietnam encompassing 19 travelers were assessed. A fecal specimen was collected from each traveler before and after each travel event and was inoculated on CHROMagar containing cefotaxime (CTX). Three to seven colonies exhibiting the characteristics of Escherichia coli were collected. Susceptibility to antibiotics and extended-spectrum β-lactamase (ESBL) production were determined by the disk diffusion method and the double-disk synergy test, respectively. ESBL-encoding genes were genotyped, and phylogenetic groupings were determined by multiplex polymerase chain reaction (PCR). The presence of mcr-1 was also confirmed by PCR and sequencing.
Results: A total of 175 ESBL-producing E. coli isolated before and up to 2 weeks after traveling to Vietnam were analyzed. Genotyping of ESBL-producing isolates showed that blaCTX-M-1/blaTEM (27.7%) and blaCTX-M-9 (45.9%) were the most prevalent genotypes, while the most frequently detected phylogenetic group was D (41.9%) followed by B2 (23.0%). In a significant number of travel events, travelers brought ESBL-producing E. coli back to Japan and three events by three travelers carried mcr-1. ESBL-producing E. coli isolates harboring mcr-1 were identified as those carrying both blaCTX-M-14 or blaCTX-M-55 and mcr-1.
Conclusion: Using Vietnam as an example, we have shown that even a short-term trip to some countries may result in ESBL-producing mcr-1-positive E. coli carriage by international travelers.
Authors
Tatsuya Nakayama, Yuko Kumeda, Ryuji Kawahara, Takahiro Yamaguchi, Yoshimasa Yamamoto
[link url="https://www.sciencedaily.com/releases/2018/04/180411111112.htm"]Osaka University material[/link]
[link url="https://www.dovepress.com/carriage-of-colistin-resistant-extended-spectrum-beta-lactamase-produc-peer-reviewed-article-IDR"]Infection and Drug Resistance abstract[/link]