From Joseph M. Kontra, M.D., Chief, Division of Infectious Diseases

Joseph M. Kontra, M.D.

MCR-1 is not a bacteria or a virus but a gene -- a piece of genetic material that allows a bacteria to become resistant to the antibiotic colistin. Colistin is an old drug used today as a last resort to treat infections with bacteria that are already highly resistant to most other antibiotics.
The MCR-1 gene has spread from China to many other parts of the world and will likely continue to do so. It is passed from bacteria to bacteria when they are in close proximity, like a handshake of sorts. The significance of MCR-1 is twofold. First, the report of this gene in a bacteria in the United States is a first, and has come much sooner than hoped. Secondly, when MCR-1 is present in bacteria called CREs (carbapenem-resistant-enterobacteriaceae) -- which are already highly resistant pathogens -- it can make the bacteria resistant to all currently available antibiotics, i.e. pan-resistant.
That is the so-called “super bug.” For patients with serious infections, there may therefore be no treatment available, taking us back to the early part of the 20th century before the discovery of antibiotics, when infection was a major cause of death in all age groups.
So why did this happen? Antibiotics are not a new discovery by man. Bacteria and fungi use antibiotics against each other in competition to survive and protect their own environmental niche. Genes resistant to newly “discovered” antibiotics have been found in ancient uninhabited caves and deep under permafrost dating back millions of years. The ability of bacteria to adapt and develop protective mechanisms for survival in hostile environments has been evolving for millennia, and they are quite good at it.
Overuse of antibiotics is certainly a major driver of the problem. One third of antibiotic use in humans has been estimated to be unnecessary. However, about 80 percent of the tonnage of all antibiotic use in the United States and around the world is in animals used in human food production. Where there is close proximity of humans and animals on antibiotic feeds, the natural sharing of bacteria and the ability of those bacteria to transfer these resistance genes to each other leads to humans acquiring, or becoming colonized, with the resistant germs. Such sharing of bacteria with animals (including our pets) and other humans is part of nature.  We have, through overuse of antibiotics, perverted the balance of nature, and we are now paying the price.
The good news? There is no evidence so far that MCR-1 is spreading in the United States. But there are things the public can do to keep as safe as possible against all germs. People should properly cook all meats and maintain good hand-washing and cleanliness, especially during food preparation. People should rise up, and Congress should act to limit or eliminate antibiotic use in the livestock industry.
Doctors should avoid unnecessary antibiotic prescribing, and patients should be relieved when their doctor says that they do not need an antibiotic for their cough or cold or sinus symptoms. In hospitals proper use of antibiotics (stewardship) is crucial, as is the quick identification and quarantine of patients harboring or infected with resistant germs (infection control).
There is no reason for public panic regarding MCR-1, but it should serve as yet another wake-up call for all of us.

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