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 Outbreaks of E. coli - a potentially fatal illness - are commonly
blamed on undercooked meat or raw vegetables, but when researchers
did a genetic analysis of thousands of samples, they found that most
E. coli infections in the UK were caused by a strain often found in
the human gut and in sewage, but not seen much in the food supply.
That suggests the infection is primarily being spread as a result of
human fecal particles transmitted from person to person, the study
team writes in Lancet Infectious Diseases.
David M. Livermore, a medical microbiologist at the University of
East Anglia, and his colleagues call E. coli a "Jekyll and Hyde
organism." E. coli mainly lives harmlessly in the guts of humans and
animals, but a handful of nasty strains can cause food poisoning and
bloodstream infections.
E. coli is the most common cause of bloodstream infection, or
bacteremia, in England, Livermore said in a phone interview. "Over
the past 15 years, E. coli has become substantially more resistant
to antibiotics and harder to treat," he added.
Researchers have known that superbug E. coli strains circulate in
humans and food animals like chickens. But it was unclear if the
bloodstream infections they cause are picked up from the food chain
or passed between people.
To find out, the researchers performed genome sequencing on samples
collected in 2013 and 2014 from people, animals and sewage in five
areas: London, East Anglia, Northwest England, Scotland and Wales.
The samples they compared came from human bloodstream infections,
human feces, animal slurry, as well as foods like beef, pork,
chicken, fruits and vegetables.
DNA sequencing showed that antibiotic-resistant E. coli were often
seen in sewage and on retail chicken meat, but rarely on other meats
and never on plant-based foods.
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In addition, samples of a particular antibiotic-resistant strain of
E. coli called ST131 collected from human blood, feces and sewage
all matched each other - but they didn't match strains in chicken,
cattle and animal slurry.
"It tells us the problem in humans is the circulation of
human-adapted, resistant E. coli and not infections coming down the
food chain. At least, in this particular case," Livermore explained.
"I would say one caveat was (our) study relates to the here and
now," Livermore said. "Resistant E. coli in the future could be food
chain-related."
"It is important to practice good food safety practices, but the
study demonstrates good hand hygiene to prevent transmission is by
far the most important," said Dr. Tamar Barlam, chief of infectious
diseases and director of the Antimicrobial Stewardship Program at
Boston Medical Center, who wasn't involved in the study.
Both Livermore and Barlam noted that careful hygiene is especially
important in homes for the elderly, as most of the severe E. coli
urinary tract infections and bacteremias occur in those settings.
"Nursing facilities serve as reservoirs for antibiotic-resistant
bacteria, and their residents may need help with hygiene while using
the toilet or may have urinary catheters," Barlam said.
SOURCE: https://bit.ly/2p13FnS and https://bit.ly/2PWPZVO The Lancet
Infectious Diseases, online October 22, 2019.
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