Researchers in New Jersey have found what they believe is the first strain of E. coli in the U.S. with two genes that make it resistant to both carbapenems, broad-spectrum antibiotics, as well as colistin, which is considered the antibiotic of last resort. They published their findings in mBio.
Barry Kreiswirth, PhD, director of the Public Health Research Institute Tuberculosis Center at New Jersey Medical School in Newark, and his team reexamined bacterial isolates for the mcr-1 gene, which makes bacteria resistant to colisin, after Chinese researchers published findings on the gene last fall.
One isolate was from a patient at University Hospital in Newark who had undergone radiation therapy for prostate cancer and then developed recurrent urinary tract infections. That sample showed an E. coli strain that not only carried the mcr-1 gene, but also the blaNDM-5, which confers resistance to carbapenem antibiotics.
This is different from the untreatable superbug found in Pennsylvania earlier this year, which carried only the mcr-1 gene.
"Others in the U.S. have found mcr-1 positives, but the significance of this paper was this was the first example so far in our country of having the colistin resistance associated within the same strain as carbapenem resistance," Dr. Kreiswirth told mBiosphere.
In this case, the man was treated successfully with piperacillin/tazobactam and vancomycin.
Jose Mediavilla, the study's main author, said he fears this strain could easily be spread in the community.
"These strains are probably already in the community and could spread further, essentially building toward a situation where you're going to have difficult if not impossible to treat urinary tract infections," he said. "Active surveillance efforts involving all colistin- and carbapenem-resistant organisms are imperative to determine mcr-1 prevalence and prevent further dissemination."