Medical detectives said Friday they are still baffled about how much-feared drug-resistant superbugs infected two people in the U.S. this year, but they have good news: both patients recovered and don't seem to have infected anyone else.
The medical team also reported the fourth known case in the U.S., involving a Connecticut toddler.
The case of a woman in Pennsylvania startled public health officials and made headlines last May.
She was found to be carrying E. coli bacteria that had acquired a gene called mcr-1. This gene gives bacteria the ability to withstand the effects of last-ditch antibiotics.
Luckily, the women recovered and did not appear to infect anyone else, the team at the Pennsylvania Department of Health and the Centers for Disease Control and Prevention reported.
"These findings suggest that the risk for transmission from a colonized patient to otherwise healthy persons, including persons with substantial exposure to the patient, might be relatively low," they wrote in a report released by the CDC Friday.
Scientists fear an E. coli bacteria with the mcr-1 gene could pass it to another superbug with other mutations -- creating a true superbug that resists all known antibiotics.
They've been looking for mcr-1 since it was first seen in China in 2015. News of the Pennsylvania patient was so alarming that CDC Director Dr. Tom Frieden at first told reporters the infection was indeed resistant to all known antibiotics. Doctors later clarified that this particular infection only involved the mcr-1 gene and the patient had in fact recovered.
What makes mcr-1 more frightening is that it's found on a plasmid. Bacteria can easily swamp this little stretch of DNA back and forth, helping pass along the superbug trait.
Source : http://www.nbcnews.com/health/health-care/superbug-source-remains-mystery-n645641