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 Army scientists in May reported finding E. coli bacteria that harbor
a gene which renders the antibiotic colistin useless. The gene,
called mcr-1, was found in a urine sample of a Pennsylvania woman
being treated for a urinary tract infection.
On Monday, researchers confirmed preliminary findings that E. coli
carrying the same mcr-1 gene were found in a stored bacterial sample
of a New York patient who had been treated for an infection last
year, as well as in patient samples from nine other countries.
The report came from a global effort called the SENTRY Antimicrobial
Surveillance Program, led by Mariana Castanheira of JMI Laboratories
based in North Liberty, Iowa.
The mcr-1 superbug has been identified over the past six months in
farm animals and people in about 20 countries, including China,
Germany and Italy.
The bacteria can be transmitted by fecal contact and poor hygiene,
which suggests a far wider likely presence than the documented cases
so far, according to leading infectious disease experts.
Health officials fear the mcr-1 gene, carried by a highly mobile
piece of DNA called a plasmid, will soon be found in bacteria
already resistant to all or virtually all other types of
antibiotics, potentially making infections untreatable.
"You can be sure (mcr-1) is already in the guts of people throughout
the United States and will continue to spread," said Dr. Brad
Spellberg, professor of medicine at the University of Southern
California.
Dr. David Van Duin, an infectious disease expert at the University
of North Carolina in Chapel Hill, said he expects more documented
U.S. cases of mcr-1 in coming months because it is already here and
will spread from abroad. "We will see a lot more of this gene."
Colistin causes kidney damage, but doctors have opted for it as
other antibiotics increasingly fail. Its overuse, especially in
overseas farm animals, has allowed bacteria to develop resistance to
it.
PAST AND PRESENT INFECTIONS
To track the mcr-1 gene, U.S. hospitals are working together with
state and federal agencies to test bacteria samples of patients that
have recently been treated for infections. Many of the largest
research hospitals are examining samples of antibiotic-resistant
bacteria that have long been stored in their freezers.
Gautam Dantas, associate professor of pathology at Washington
University Medical Center in St. Louis, has tested hundreds of U.S.
samples of archived bacteria in recent months and has not yet
detected mcr-1. But he expects dozens of confirmed cases of the gene
will be documented by next year in the country, mostly among current
patients.
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The concern of many disease experts is that mcr-1 could soon show up
in bacteria also resistant to carbapenems, one of the few remaining
dependable classes of antibiotics. In that event, with colistin no
longer a last-ditch option, some patients would have to rely on
their immune systems to fight off infection.
"Within the next two to three years, it's going to be fairly routine
for infections to occur in the United States for which we have no
(effective) drugs available," Dantas said.
Castanheira also believes mcr-1 will find its way into carbapenem-resistant
bacteria, formally known as carbapenem-resistant enterobacteriaceae
(CRE).
In an interview, she said the resulting virtually impervious
bacterium would likely spread slowly inside the United States
because CRE themselves are not yet widespread in the country, giving
drugmakers some time to create new antibiotics.
Beginning in August, the U.S. Centers for Disease Control and
Prevention will use $21 million to expand surveillance at
laboratories operated by all 50 state health departments and seven
larger regional labs. The federal funding will help pay for
more-sensitive equipment to test for antibiotic resistance in
bacteria samples provided by hospitals.
Jean Patel, deputy director of the CDC's Office of Antimicrobial
Resistance, said the effort will provide the CDC improved national
surveillance of antibiotic-resistance trends, including any spread
of mcr-1.
"This is data for action," she said, adding that special procedures
to prevent infections from spreading in hospitals could be taken
once a patient is identified with mcr-1 related infections or with
multidrug-resistant bacteria.
(Reporting by Ransdell Pierson; Editing by Marguerita Choy)
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