Tourists Can Import Antibiotic-Resistant Superbugs

A new study published by Odette J. Bernasconi, MSc, University of Bern, Switzerland, and colleagues in Antimicrobial Agents and Chemotherapy, has shown that tourists can acquire multidrug-resistant bacteria when they travel—including colistin-resistant strains of Escherichia coli, some of which may possess the mcr-1 gene which protects bacteria against the last-resort antibiotic, colistin.

According to corresponding author, Andrea Endimiani, MD, PhD, this mechanism of colistin resistance related to the mcr-1 gene emerged in November 2015, “with a high prevalence in Escherichia coli and Klebsiella pneumoniae strains detected in China among humans, food animals, and chicken meat; more recently, it has also been found in other countries.”

This gene is plasmid-mediated, notes Dr Endimiani, “thus assuring its great ability to mobilize and spread between different enterobacteria, including those normally present in the human and animal intestinal tracts.”

In their study, the researchers examined the population of bacteria in the intestinal tracts of 38 individuals who had returned to Switzerland after traveling to India; 39% of the participants had experienced traveler’s diarrhea, but had not received any antibiotics.

Dr. Bernasconi and colleagues analyzed stool samples from the travelers, both before and after their trips, and found that the intestinal tracts of 76% of these individuals were colonized with superbugs.

More concerning, however, the researchers showed that 11% of the travelers had colistin-resistant E. coli strains in their stool samples, including strains with the new plasmid-mediated mcr-1 gene. The results of molecular studies performed by the researchers also suggested that the travelers acquired these resistant bacteria during their stay in India, either from the environment or the food chain.

Because these colistin-resistant Enterobacteriaceae with the plasmid-mediated mcr-1 gene have been isolated globally from humans, food-producing animals, the food chain, and the environment, their emergence represents a serious public health concern.

In conclusion, Dr Endimiani therefore recommends “a rapid implementation of specific and sensitive surveillance programs to prevent unexpected outbreaks due to enterobacteria possessing the mcr-1 gene”.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.