We thought it was a one-time deal, but as it turns out, we were mistaken. Researchers have revealed that, back in 2015, they identified a sample of human bacteria containing a superbug that defies the effects of a last-ditch antibiotic.
An Iowa company that tests samples said the patient in New York was infected with E. coli bacteria carrying a gene called MCR-1, meaning it has been two times now that the superbug has been discovered in a U.S.-based sample. The other time (technically the second) was earlier this year, when a team at the Walter Reed Army Institute of Research found the MCR-1 gene in a sample taken from a woman in Pennsylvania.
Publishing the findings in the American Society for Microbiology journal Antimicrobial Agents and Chemotherapy, researchers revealed that, out of the 20,000 samples tested, only 19 carried the MCR-1 gene — with only one being from the U.S.
These 19 MCR-1 harboring isolates, collected in 2014 and 2015 as part of the Sentry Antimicrobial Surveillance Program, were found among 13,526 E. coli and 7,480 K pneumoniae isolates from 183 hospitals in the Asia-Pacific region, Europe, Latin America and North America. Out of the roughly 20,000 relevant isolates identified, only 390 of them showed colistin. On the other hand, all of the K pneumoniae isolates tested negative for MCR-1.
So, what's the deal here? In theory, 19 cases isn't a big deal and should hardly be considered a serious case — right?
Unfortunately, researchers don't think so. Why? Because the MCR-1 gene is carried on mobile pieces of DNA called plasmids, which grant it the ability to move to other types of human and animal bacteria and pass on its colistin resistance to those germs. This is only part of the problem, though. The issue in this case is the germs to which the MCR-1 gene has the potential to grant its colistin resistance.
Typically, colistin isn't often used against most germs, but it's the only line of defense against the superbug known as CRE, a family of drug-resistant bacteria. Simply put, the prospect of a gene bouncing around that could confer resistance to an agent that is used as our final line against drug-reistant bacteria isn't one to be taken lightly.
Fortunately, in this instance, none of the samples were ultimate superbugs, as they were all treatable with other antibiotics.
"Most isolates were susceptible to cephalosporins, and were all susceptible to carbapenems, amikacin, tigecycline and ceftazidime-avibactam, among other agents," the team wrote.
