Researchers have long suspected a link between the E. coli that causes human urinary tract infections and E. coli contamination in meat products, and new research gives more credence to the theory.
A study published in the Centers for Disease Control and Prevention’s Emerging Infectious Diseases journal found genetic similarities between E. coli from animals sampled at slaughterhouses and the E. coli that causes UTIs and concluded that chickens were the most likely reservoir.
Urinary tract infections (UTIs) are the second most common type of infection in the body, accounting for 8.1 million visits to health care providers in the United States each year and around $1-2 billion per year in health care costs. Around 85 percent of these infections are caused by extraintestinal pathogenic Escherichia coli, or ExPEC, which doctors long assumed came from patient’s own intestines. New research, however, has been looking at outside sources as potentially part of the problem.
The relatively recent emergence of drug-resistant E. coli has made UTI infections more complicated and expensive to treat, which makes understanding E. coli reservoirs even more important.
The latest study, which was conducted by researchers at several Canadian universities, collected 531 E. coli isolates from people with UTIs in Montreal and another 124 isolates from people across Canada and compared them to 737 isolates from beef, chicken and pork products sampled at the retail level from Montreal and elsewhere. They also took 349 samples from the same food animals in slaughterhouses.
The researchers concluded that beef and pork isolates were much less likely than chicken isolates to be “clonal related” to isolates from humans with UTIs and they hypothesized that food could be a source of transmission.
“This study confirms our hypothesis that chickens are a likely reservoir for ExPEC in humans,” reads the study. “However, epidemiologic data, such as diet or other exposures, were not available for the humans with UTIs. This information could have been used to search for other potential routes of transmission (e.g., travel, water sources) and to strengthen the connection between poultry consumption and UTI.”
The researchers used an ecological design for their study, which means that isolates were systematically and purposely selected, or rather: meat samples were taken near the same communities that suffered the UTIs.
The study’s authors said the results from their analysis suggest that “potential ExPEC transmission from food animal sources is likely to be implicated in human infections and that chicken is a major reservoir.”
They added: “The possibility that ExPEC causing UTIs and other extraintestinal infections in humans could originate from a food animal reservoir raises public health concern. New interventions may be needed to reduce the level of food contamination and risk for transmission.”
Amee Manges, associate professor of epidemiology and biostatistics at McGill University in Montreal told Food Safety News her team is now working on a pan-Canadian study to examine this issue more closely and the study will include
collecting epidemiologic information from women experiencing urinary
“We will also be
comparing the E. coli causing infections in these women to E. coli
recovered from retail meat (through the Public Health Agency of Canada’s
surveillance program entitled Canadian Integrated Program on
Antimicrobial Resistance Surveillance) from the same geographic areas in
which the UTIs are occurring,” said Manges. “This should give us more information
about the spread of these E. coli and hopefully help establish the
existence of a food reservoir.”
Asked about whether anything about the findings surprised the researchers, Manges brought up drug-resistance.
We are most worried about the selection and amplification of
drug-resistant E. coli on the farms because of improper or overuse of
antimicrobials during food animal production,” she said. “It may be possible to
reduce the level of drug-resistant infections in humans by encouraging
rationale and judicious use of antimicrobials on farms. Changing how
food animals are produced could help as well. Other approaches might
include treating meats to reduce retail meat contamination by E. coli
and encouraging better food handling practices.”
“Prevention of E. coli urinary tract infections in people might need to start on chicken farms,” read a CDC summary of the study.
The National Chicken Council questioned the findings.
“While we question the overall conclusions of this study, the study’s researchers point to improper food handling during meat preparation for food-borne UTIs,” said council spokesman Tom Super. “So it is always pertinent to remind consumers about the importance of safe food handling and cooking – washing of hands, cutting boards and utensils, cooking chicken to an internal temperature of 165 degrees F and preventing cross contamination in the kitchen.”
This story has been updated to include feedback from researcher Amee Manges.