This is the conclusion of a new study in which – and this is particularly worrying – until recently unknown antibiotic-resistant genes have also been discovered.
That can be read in the magazine Genome Medicine. An international team of researchers – including scientists from Maastricht University – analyzed poop samples from 190 Dutch travelers for the study. The travelers provided a poo sample before leaving for Southeast Asia, South Asia, North Africa and East Africa. And did the same after arriving.
The research shows that in addition to a suitcase filled with souvenirs and dirty laundry, the world travelers also bring home quite a few multi-resistant intestinal bacteria. And once home, they can pass it on to family, friends and others they come into contact with. And in this way the world travelers contribute to the spread of the dreaded super bacteria: bacteria that cannot or can hardly be combated with antibiotics.
“Before the COVID-19 pandemic, we already knew that international travel was contributing to the rapid global rise and spread of antibiotic resistance,” said study researcher Alaric D’Souza. “But what is new is that we have found several completely new genes that are associated with antibiotic resistance. It suggests a worrisome problem awaits us.”
In their study, the researchers focused on travelers who visited four regions: North and East Africa, Southeast and South Asia. These are areas where antibiotic-resistant genes are common. It can be traced back to poor sanitation, among other things, which causes bacteria to flourish. Due to the high population density, the bacteria also spread quite easily.
As D’Souza points out, this isn’t the first study looking at the role of world travelers in the spread of multidrug resistant bacteria. During previous studies, however, only genetic material that belonged to the resistant bacteria known to us was sought. This study went one step further and examined all the genes found in the poo samples. This approach allows researchers to pinpoint both known and new antibiotic-resistant genes.
In total, the researchers discovered 121 antibiotic-resistant genes in the faeces samples. More than 40 percent of them would not have surfaced during a search that focused on known resistant pathogens, the researchers say. It points out that with this widely used approach, many potentially dangerous genes are overlooked.
ESBL and mcr-1
What’s equally troubling is that 56 of the 121 antibiotic-resistant genes were only found in poop samples people donated after their trip. It shows that people actually got them abroad. Among those genes collected abroad were the ESBL gene and mcr-1. The ESBL gene is on the rise worldwide and is causing bacteria to become resistant to penicillin and other commonly used antibiotics. The mcr-1 gene protects bacteria from an antibiotic called colistin, which serves as a last resort in the fight against multidrug-resistant bacteria. If this gene spreads to those multi-resistant bacteria, infections caused by these pathogens can no longer be fought.
Antibiotic-resistant genes actually made their way into our gut naturally. Gut bacteria evolved the genes over thousands of years through exposure to antibiotics naturally produced by environmental bacteria. But the overuse of antibiotics in healthcare and livestock has accelerated this process. For example, repeated exposure to antibiotics can cause bacteria to stop responding to antibiotics after some time. But bacteria can also become resistant overnight, through a so-called horizontal gene transfer. This involves the exchange of genetic material. This material resides on ‘mobile genetic elements’. “Since the genes that cause a bacterium to become resistant to different types of antibiotics are often located on the same mobile elements, a single horizontal gene transfer can cause a bacterium that was previously susceptible to antibiotics to turn into a multi-resistant organism,” said study researcher Gautam. dantas.
The results are alarming. “Multi-resistant bacteria are one of the biggest public health problems worldwide in the near future,” says researcher John Penders, of Maastricht University. “Estimates indicate that by 2050, more people may die from infections caused by multidrug-resistant microorganisms than currently from cardiovascular disease or cancer.” It is therefore very important to avert this crisis. And the new research suggests we shouldn’t overlook the role world travelers play in this story, either. “The results strongly suggest that international travel is a vector for the global spread of antibiotic-resistant genes and reveals the need to better monitor the antibiotic-resistant bacteria in the gut of returning travelers,” said D’Souza. “Identifying new antibiotic-resistant bacteria and genes could play an important role in slowing the global spread of resistance.”