CDC Reports First Cases of Antibiotic-Resistant Gene Found in Bacteria in US

By Jeannette Richard | June 20, 2016 | 6:04pm EDT
The Centers for Disease Control and Prevention in Atlanta. (AP photo)

( -- Scientists have discovered the first cases in the U.S. of a gene that renders infectious bacteria resistant to the “last-resort” antibiotic drug colistin, a Centers for Disease Control and Prevention (CDC) official testified last week during a congressional hearing on the danger posed by “superbugs”.

The Department of Defense (DOD) first identified the mcr-1 gene in E. coli bacteria in a urine sample taken from a Pennsylvania woman "with no recent travel outside of the country.” 

The infected woman was “treated in an outpatient military treatment facility in Pennsylvania,” according to the U.S. Dept. of Health and Human Services (HHS), which noted that the mcr-1 gene has also been found in Europe and Canada.

“In May, Department of Defense scientists announced the first discovery of the mcr-1 gene in bacteria isolated from a person in the United States. Although there is not an immediate threat to the public or the current health of this patient, this is an important development for the United States," Dr. Beth Bell, the director of CDC’s National Center for Emerging and Zoonotic Infectious Disease, told the House Committee on Energy and Commerce.

"The antibotic colistin is used as a rescue drug to treat patients with multiple drug-resistant infections, like CRE [Carbapenem-resistant Enterobacteriaceae]," Bell testified. "The mcr-1 gene makes bacteria very resistant to colistin. 

"The gene exists on a plasmid, a small piece of DNA that is capable of moving from one bacterium to another, spreading antibiotic resistance among bacterial species,” Bell explained. "The presence of the mcr-1 gene and its ability to share its colistin resistance with other bacteria such as CRE raises the possibility of a bacteria that is resistant to every antibiotic. 

"USDA [Dept. of Agriculture] also discovered mcr-1 in E.coli isolates collected from two different pig intestines. By comparing the DNA sequences of all three isolates, federal scientists have determined that the isolates from the pigs are different from the human."

Bell noted that CDC has issued an alert informing states about "new detection tools for mcr-1".

“Antibiotic resistance is perhaps the single most important infectious disease threat of our time,” Bell warned in her written testimony. “Every year, more than two million people in the United States get infections that are resistant to antibiotics, and at least 23,000 people die as a result...Modern medicine is at stake.”

The discovery of mcr-1 is very alarming to public health officials because "nightmare bacteria" such as CRE  are already difficult to fight because of their resistance to many other antibiotics.

“The bacteria identified is not resistant to all antibiotics (referred to as a pan-resistant infection). The presence of the mcr-1 gene, however, and its ability to share its colistin resistance with other bacteria, such as CRE, raises the possibility that pan-resistant bacteria could develop,” Bell testified.

"The identification of mcr-1 vividly illustrates our domestic and global challenges of antibiotic resistance," she added. After first being discovered in China last November, "in less than six months [the gene] has been identified in two animals and a human in the United States."

However, “as of April 2016, more than 44,000 Salmonella and 9,000 E.coli/Shigella isolates from NARMS [the National Antimicrobial Resistance Monitory System] as well as the National Center for Biotechnology Information genomic database did not show the presence of the mcr-1 gene,” HHS reported, reminding Americans that “cooking all meat, poultry and fish to its proper temperature kills bacteria, viruses and other foodborne pathogens whether or not they are antibiotic-resistant.”

Antibiotic resistance in bacteria has been a growing problem in recent years.

“Historically, when an infection demonstrated resistance to one class of antibiotics, clinicians would simply switch to a different class. However, the past two decades have witnessed a significant increase in the spread of organisms resistant to multiple classes of antibiotics,” explained Dr. Richard Hatchett, acting director of the Biomedical Advanced Research and Development Authority, at the hearing.

“Compounding the problem, the pace of introductions of new antibiotics has slowed considerably largely because there is not a sufficient private sector incentive to invest in antibiotic development,” Hatchett said.

The overuse of antibiotics has also contributed to the rise of antibiotic resistance, according to Dr. Janet Woodcock of the Food and Drug Administration (FDA).

“The inappropriate use of antibacterial drugs can accelerate the development of antibiotic resistance. It is essential that we use antibiotic drugs prudently in order to preserve the effectiveness of these drugs,” she said.

The CDC estimated that 30 percent of antibiotic prescriptions are unnecessary in a study released last month.

The development of vaccines can help prevent the overuse of antibiotics as well as prevent infections for which antibiotics are no longer effective, Dr. Dennis Dixon of the National Institute of Allergy and Infectious Disease (NIAID), an arm of the National Institutes of Health, told the committee.

“NIAID is developing vaccines to prevent infections for which treatment options are jeopardized by the emergence of drug resistance...Vaccines for viral infections such as influenza also may help reduce the use of antibiotics, which are often used inappropriately to treat viral infections, or appropriately used to treat bacterial infections that sometimes develop following viral infections,” Dixon said.

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