US researchers find bacteria resistant to last-resort drug

Back in November, researchers from China reported finding a gene that confers resistance to the last-resort antibiotic colistin in several E. coli isolates, and warned that pan-drug resistant Enterobacteriaceae -- a family of bacteria that includes common foodborne illness culprits E. coli and Salmonella -- "is inevitable and will ultimately become global." As researchers in other countries began examining stored isolates for the gene, MCR-1, they found it. STAT's Helen Branswell reports it "has been found in many European countries, parts of Asia, North Africa, South America, and North America, including Canada."

Last week, researchers from the Walter Reed Army Institute of Research reported in Antimicrobial Agents and Chemotherapy that they've found MCR-1 in the U.S. Specifically, they identified it in E. coli cultured from the urine of a 49-year-old Pennsylvania woman with symptoms of a urinary tract infection. Patrick McGann and his co-authors note, "the patient reported no travel history within the prior 5 months." And they found the gene within three weeks of launching systematic efforts to look for it. Maryn McKenna reports at Germination:

The Pennsylvania woman’s diagnosis occurred thanks to a system set up within the DOD after MCR was discovered. Since last fall, any E. coli that was already resistant to a family of drugs known as ESBLs (extended-spectrum beta-lactams), as hers was, has been sent up the chain to Walter Reed, to be scrutinized for colistin resistance. That kind of systematic checking for antibiotic resistance, known as active surveillance, is rare in the United States. Most civilian surveillance systems are patchy; they focus only on foodborne illnesses, or rely on physicians or labs to report diagnoses, or draw from a few state health departments with already well-funded labs.

In addition to this discovery by the Department of Defense, an HHS.gov blog post reports, "A USDA and HHS search for colistin-resistant bacteria in food animals, retail meats and people also has found colistin-resistant E. coli in a single sample from a pig intestine." Over the past year, these three agencies have been involved in surveillance and research activities as part of President Obama's National Action Plan for Combating Antibiotic-Resistant Bacteria.

MCR-1 is of particular concern because it's carried on a plasmid, a small piece of DNA that can easily transfer from one strain of bacteria to another. While the bacteria from the Pennsylvania woman was susceptible to some antibiotics, the fear is that a separate multi-drug resistant bacteria -- like "nightmare bacteria" carbapenem-resistant Enterobacteriaceae (CRE) -- could acquire MCR-1. In other words, we could soon be facing bacteria that are resistant to all antibiotics currently available. In such a "post-antibiotics future," medical procedures that are now routine, like dialysis or hip replacements, could carry the risk of untreatable infections.

The fact that US agencies discovered MCR-1 in a human patient and animal sample is a sign of success for their new surveillance efforts. CDC and USDA are investigating possible sources of these infections and working to identify any other cases. Worldwide, surveillance efforts have succeded in identifying MCR-1 in samples from a variety of sources in several diffeent countries. Where we're lagging, though, is in adressing the root of the problem: inappropriate use of antibiotics. Lance Price of the Antibiotic Resistance Action Center (ARAC) at the George Washington University Milken Institute School of Public Health (where I also work) had this statement:

Much like in the U.S., Chinese livestock producers are overusing antibiotics to prevent diseases and make animals grow faster. Colistin is widely used in Chinese livestock and this use likely led to the evolution of mcr-1. This promiscuous gene can be transferred from bacterium to bacterium, increasing the likelihood that it will find its way to CRE. History shows that mobile resistance genes can spread quickly around the world, silently riding in people, animals, and food. We’re watching this scenario play out in real time.

Scientists rang the alarm bells about mcr-1 back in November, but the attention didn’t last much longer than an average news cycle. Now we find that this gene has made its way into pigs and people in the U.S. If our leaders were waiting to act until they could see the cliff’s edge—I hope this opens their eyes to the abyss that lies before us. It’s time to act. We need a global agreement to end the abuse of all medically important antibiotics in livestock production in the U.S. and around the world.

I wish I could express some optimism about the likelihood of US leaders responding to this threat with the force and urgency it deserves. But if our current Congress can't even approve sufficient funds for Zika virus response, when the virus is already circulating in Puerto Rico, I fear they won't consider the MCR-1 discovery to be the wake-up call it ought to be.