Travellers import "super germs"
University of Bern. Three out of four tourists who returned to Switzerland from India were infected with multi-resistant germs during an investigation.
Microbiologists from the University of Bern have also been able to isolate a bacterial strain that has a gene that enables these dangerous pathogens to become resistant to the currently only effective antibiotic therapy.
The spread of multi-resistant bacteria poses challenges to health systems around the world, as the therapeutic options due to antibiotics are dwindling. These “super germs” can cause serious infections and often lead to a serious and fatal course of the disease. It is already estimated that 700 people worldwide die each year because antibiotics have become ineffective for them. Until now, such infections could only be treated with the antibiotic colistin.
In November 2015, however, a widespread resistance to colistin was also discovered in strains of the bacteria Escherichia coli and Klebsiella pneumoniae. These bacterial strains were found in China in the intestinal tract of humans, farm animals and poultry meat; meanwhile they have also appeared in other countries.
Colistin resistance is caused by a gene called the mcr-1 gene.
This gene is passed on through plasmids - DNA molecules in bacteria - and can therefore spread unhindered in various intestinal bacteria, including the natural intestinal flora of humans and animals. In humans, E. coli can cause urinary tract infections, blood poisoning and other infections, while K. pneumoniae mainly causes urinary and respiratory infections.
Microbiologists at the Institute for Infectious Diseases at the University of Bern have now for the first time examined the bacterial population in the intestines of travelers returning to Switzerland from India. They found that 76% of returning tourists were colonized with multi-resistant strains of bacteria. "More seriously, 11% of travelers had colistin-resistant strains in their stool samples, including those that contained the new plasmid-mediated mcr-1 gene," says Prof. Andrea Endimiani, lead author of the study. The results have now been published in the journal “Antimicrobial Agents and Chemotherapy”.
Widespread colistin resistance
The mcr-1 gene has already been isolated in several studies in colistin-resistant intestinal bacteria from humans, farm animals, in the food chain and also in the environment. Most of these studies, however, examined samples previously collected for this purpose. "We now wanted to find out what the current distribution of this gene in multi-resistant intestinal bacteria looks like," says Endimiani. "Mainly because it is already known that returning travelers are very often infected with super-germs."
Endimiani and his team examined stool samples from 38 people from Switzerland before and after a trip to India in 2015. The average length of stay in India was 18 days. The study participants frequently visited other countries in the 12 months prior to their trip to India, but never suffered from diarrhea. On their return from India, however, 39% suffered from travel-related diarrhea and additional symptoms. Antibiotics were not taken. The researchers were surprised by the high rate of multi-resistant intestinal bacteria discovered: 76% of travelers returned with super germs. 11% of these had strains resistant to the final antibiotic option, colistin. One of these streams also possessed the mcr-1 gene, which can promote and spread colistin resistance in other intestinal bacteria in humans and animals.
Molecular analyzes showed that these life-threatening bacteria had been ingested through the environment or through the food chain in India. There is also a high risk for healthy carriers of super germs if they develop urinary tract infections or blood poisoning at a later date, as these pathogens are then difficult to combat.
"Infection with colistin-resistant bacteria while traveling is a phenomenon that we have to watch carefully in order to prevent the spread of such untreatable super-germs in Switzerland - a country that is still relatively untouched by this problem," says Endimiani .
The researchers therefore recommend that specific and close-knit monitoring programs be introduced quickly in order to prevent unexpected outbreaks of disease due to intestinal bacteria with the mcr-1 gene.
Swiss Center for Antibiotic Resistance
The University of Bern has a long tradition in antibiotic resistance research and, with the Institute for Infectious Diseases, is a leader in the investigation and control of super-germs. The Swiss Center for Antibiotic Resistance (ANRESIS) is located at the institute. ANRESIS is a regional and national monitoring system and research instrument for antibiotic resistance and antibiotic consumption in human medicine. The project is financed by the Federal Office of Public Health (FOPH), the Swiss Conference of Cantonal Health Directors (GDK) and the University of Bern.
Publication information:
Bernasconi OJ, Kuenzli E, Pires J, Tinguely R, Carattoli A, Hatz C, Perreten V, Endimiani A .: Travelers Can Import Colistin-Resistant Enterobacteriaceae Including Those Possessing the Plasmid-Mediated mcr-1 Gene. Antimicrob Agents Chemother, June 13, 2016 pii: AAC.00731-16. [Epub ahead of print] PubMed PMID: 27297483.
