A strain of Escherichia coli with immunity to last-resort antibiotics can be destroyed with a novel combination of three existing drugs, according to researchers at the University at Buffalo, New York.
The bacterium carries two genes, mcr-1 and ndm-5, which together can resist all antibiotics.
In a study published in mBio, a journal of the American Society of Microbiology (online, 25 July 2017), the researchers reported that a combination of aztreonam, amikacin and polymyxin B (a last-resort antibiotic) destroyed the resistant E coli in 24 hours, with no subsequent regrowth
Brian Tsuji, one of the two senior authors of the study, said it was the first time that three drugs had been used against bacteria expressing the mcr-1 and ndm-5 genes. He described mcr-1 and ndm-5 strains as “an urgent threat”, because of their high degree of resistance and their potential to spread rapidly in the community.
Another co-author, Zackery Bulman, said the team believed that “the appearance of mcr-1 and ndm-5 in patients may be a harbinger for what is to come.
“The golden era of antibiotics isn’t over yet, but we wanted to help clinicians prepare therapeutically for the occurrence of these strains.”
The team described the finding as “promising”, adding that it could lead to a viable treatment against mcr-1 and ndm-5 strains.
 Bulman Z, Chen L, Walsh T et al. Polymyxin combinations combat Escherichia coli harboring mcr-1 and blaNDM-5: preparation for a postantibiotic era. mBio [Online] 2017;8(4). doi: 10.1128/mBio.00540-17