A newly discovered antibiotic-resistant gene is threatening to open a new front in the war against “superbugs” by rendering a last-resort drug ineffective, experts warn. Dubbed mcr-1, the resistance-conferring gene easily transfers among bacteria found in humans, animals, or the environment. The gene’s resistance to colistin, an antibiotic that has been around for almost 60 years, is the latest frustration for physicians, whose arsenal of effective antibiotics is rapidly shrinking.
First identified in China in November 2015, mcr-1 has since been discovered in livestock, water, meat, and vegetables for human consumption in several countries, and in humans infected with Escherichia coli—one of the disease-causing bacteria it targets.
Now the mcr-1 gene has been found in the gut of healthy humans, according to a report presented at the European Society of Clinical Microbiology and Infectious Diseases, held in Amsterdam.
“[A] key element for the emergence of superpathogens has made its way to our bodies,” Dr. Aycan Gundogdu of Turkey’s Erciyes University told attendees. “It is [only] a matter of time [before] the dissemination of [the] mcr-1 gene will be prevalent in the clinic, bringing the world closer to an antibiotic crisis.”
Colistin has been available since 1959 to treat infections caused by gram-negative bacteria—a group that includes food-poisoning E. coli and Salmonella organisms, as well as Acinetobacter, which can cause pneumonia or serious blood and wound infections. Colistin was abandoned for use in humans in the 1980s because of hepatic toxicity, but it was widely used in livestock farming, especially in China. As bacteria began to develop resistance to other, more-modern drugs, colistin was brought back as a treatment of last resort in hospitals and clinics. Now resistance to that drug, too, is becoming a problem.
Gundogdu and his colleagues analyzed DNA in fecal samples from individuals in China, Europe, and Turkey. Of the 344 Chinese subjects, six harbored the mcr-1 gene in their gut—a known major reservoir of drug resistance, according to the investigators.
Another research team, which retrospectively tested stored E. coli and Salmonella samples from food-producing animals, said that the gene has been in Europe for more than a decade.
Resistance to drugs can emerge through changes in a bacterium’s genetic code—altering the target on its surface to which antibiotics would normally bind, making the germ impenetrable. These “supergerbugs” spread easily with human help, according to Gundogdu. The wrong antibiotics, taken for too short a period or in too low a dose, help them proliferate.
The World Health Organization (WHO) has warned that drug resistance “threatens a return to the pre-antibiotic era.” In the United States, the annual cost of treating drug-resistant illnesses has been estimated at $20 billion.
Source: Medical Xpress; April 11, 2016.