> ## Content Index > Fetch the complete content index at: https://www.theamericanquorum.com/llms.txt > Use this file to discover other available public pages before exploring further. # First U.S. Patient Found With Transferable Resistance to Last-Resort Antibiotic - URL: https://www.theamericanquorum.com/first-us-patient-mcr1-colistin-resistance/ - Published: 2016-05-29T03:59:00.000Z - Updated: 2016-05-29T03:59:00.000Z - Description: Military researchers identified the transferable mcr-1 colistin-resistance gene in a Pennsylvania patient, intensifying concern that bacteria could evade every available antibiotic. - Author: Kenneth R. Deans Jr. - Tags: Healthcare, #Import 2026-08-30 08:26 A 49-year-old Pennsylvania woman has become the first patient in the United States known to carry bacteria with a transferable gene that defeats colistin, an antibiotic reserved for some of the most dangerous drug-resistant infections. The discovery does not mean the woman’s infection was untreatable, but it raises the prospect that the gene could move into bacteria already resistant to every other useful drug. Researchers at Walter Reed Army Institute of Research identified the gene, known as mcr-1, in an Escherichia coli isolate taken from the patient’s urine. Their [report published online Thursday in Antimicrobial Agents and Chemotherapy](https://pmc.ncbi.nlm.nih.gov/articles/PMC4914657/?ref=theamericanquorum.com) found 15 resistance genes on two plasmids—mobile pieces of DNA capable of moving among bacteria. The patient had symptoms of a urinary tract infection and reported no international travel in the previous five months. ## The danger lies in a gene that can move Colistin is an old antibiotic with risks of kidney and nerve toxicity. Physicians largely abandoned it when safer drugs were available, but have returned to it as Gram-negative bacteria acquired resistance to stronger modern antibiotics, including carbapenems. For some patients with those infections, colistin is the final option. Resistance to colistin has existed before, usually through mutations held within a bacterium’s chromosome. Those changes could pass to descendants but did not readily jump to unrelated bacteria. Mcr-1 is different because it is carried on a plasmid. Bacteria exchange plasmids, potentially spreading resistance across strains and species. That mechanism is why the Pennsylvania finding matters more than the clinical severity of this particular infection. The E. coli remained susceptible to several other drugs, and officials cautioned against describing it as resistant to all antibiotics. But if the same plasmid enters a carbapenem-resistant Enterobacteriaceae organism, clinicians could confront an infection with no reliable treatment. The [U.S. Military HIV Research Program’s May 26 announcement](https://www.sciencedaily.com/releases/2016/05/160526152033.htm?ref=theamericanquorum.com) said no safe dose of colistin would have treated this isolate and called the gene transferable. Colonel Emil Lesho, director of Walter Reed’s Multidrug-resistant Organism Repository and Surveillance Network, said the repository’s combined source, susceptibility and genetic data allow investigators to identify changes and trace emerging organisms. ## A global alarm reaches American soil Scientists in China first reported mcr-1 in November after finding it in E. coli from pigs, retail meat and hospitalized patients. Their discovery overturned the assumption that transferable colistin resistance was rare or absent. Within months, researchers detected the gene in Europe, Canada and elsewhere in Asia. The original Chinese surveillance, described in [The Lancet Infectious Diseases](https://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2815%2900424-7/fulltext?ref=theamericanquorum.com), found the gene in 15 percent of raw meat samples and 21 percent of routinely sampled food animals in the areas studied, as well as in a smaller share of clinical isolates. Those findings suggested that agricultural antibiotic use might help create a reservoir from which resistance could reach people. American officials had already begun looking. The Departments of Agriculture and Health and Human Services separately found an mcr-1-positive E. coli isolate in a pig-intestine sample. There is no evidence connecting that animal sample to the Pennsylvania patient, but the two discoveries demonstrate that the gene has entered more than one part of the country’s microbial environment. [The University of Minnesota’s Center for Infectious Disease Research and Policy reported](https://www.cidrap.umn.edu/antimicrobial-stewardship/highly-resistant-mcr-1-superbug-found-us-first-time?ref=theamericanquorum.com) that the human isolate contained the gene on a novel IncF plasmid, a class already associated with spreading resistance and virulence genes among Enterobacteriaceae. Lead author Patrick McGann called continued surveillance critical for determining how often the gene is present. ## Federal agencies begin a containment search The Centers for Disease Control and Prevention is working with Pennsylvania health officials and the Defense Department to investigate the patient’s contacts and possible exposures. Laboratories are being urged to test isolates that show reduced susceptibility to colistin and to send suspicious samples for molecular analysis. At the same time, federal scientists are expanding searches among people, food animals and retail meat. The [National Antimicrobial Resistance Monitoring System’s federal notice](https://www.cdc.gov/narms/resources/mcrgene.html?ref=theamericanquorum.com) says the animal isolate was also resistant to ampicillin, streptomycin, sulfisoxazole and tetracycline, underscoring how resistance traits can cluster. Coordinated surveillance is intended to determine whether mcr-1 is newly introduced or has circulated undetected. The immediate public-health response is complicated by limited routine testing. Colistin susceptibility is technically difficult to measure, and many clinical laboratories do not test for it unless physicians request the drug. Genetic sequencing can identify mcr-1, but it is not part of ordinary care. The first case may therefore reflect better detection rather than a singular introduction. [Reuters reported Friday](https://www.reuters.com/article/world/us-sees-first-case-of-bacteria-resistant-to-last-resort-antibiotic-idUSKCN0YI08X/?ref=theamericanquorum.com) that federal officials are treating the discovery as an urgent warning while stressing that the woman’s strain is not a pan-resistant “superbug.” That distinction is important: the gene creates the potential for an untreatable combination, not proof that such a combination has occurred. ## Antibiotic stewardship becomes more urgent The finding strengthens the case for reducing unnecessary antibiotic use in medicine and agriculture. Every exposure creates selection pressure favoring organisms that can survive. Once a mobile resistance gene becomes established in bacterial populations, withdrawing a drug may slow its spread but may not eliminate it. The federal government’s National Action Plan for Combating Antibiotic-Resistant Bacteria calls for faster detection, better infection control, antibiotic stewardship and development of new drugs and diagnostic tests. Those measures operate at different points in the mechanism: stewardship reduces selection, surveillance finds emerging threats, infection control limits transmission, and research provides alternatives when existing medicines fail. The pharmaceutical pipeline remains thin for antibiotics targeting highly resistant Gram-negative organisms. New drugs are used sparingly to preserve effectiveness, limiting the revenue companies can expect. Public funding and regulatory incentives are therefore central to replenishing the arsenal. A [Washington Post report on the discovery](https://www.washingtonpost.com/news/to-your-health/wp/2016/05/26/the-superbug-that-doctors-have-been-dreading-just-reached-the-u-s/?ref=theamericanquorum.com) quoted researchers who emphasized that the patient’s E. coli could still be treated, while warning that mcr-1 could transfer to bacteria that already evade other antibiotics. The danger is biological recombination: separate resistance problems can converge in one organism. ## A warning, not yet the feared endpoint The term “superbug” can imply that the organism found in Pennsylvania cannot be stopped. That is inaccurate. The patient was treated, and officials have not reported onward transmission. [The available susceptibility findings](https://www.reuters.com/article/world/us-sees-first-case-of-bacteria-resistant-to-last-resort-antibiotic-idUSKCN0YI08X/?ref=theamericanquorum.com) show options remained. But public-health systems are designed to act before the worst case materializes. Mcr-1’s arrival in a human clinical sample means the United States can no longer regard transferable colistin resistance as a distant threat. Investigators must now determine where the gene resides, how it entered the patient, whether it has spread to contacts and how commonly laboratories have missed it. The discovery is consequential precisely because antibiotics are a shared and exhaustible resource. A plasmid invisible to patients can cross between bacteria, institutions and borders. Containing it will require the same mobility from surveillance networks—and a willingness to preserve last-resort drugs before they cease to be remedies at all.