“We estimated that approximately 8% of human extraintestinal E. coli infections (mostly urinary tract infections) in our study were caused by FZEC [foodborne zoonotic E. coli].”
- Lance B. Price, Ph.D., founder and co-director, Antibiotic Resistance Center, George Washington University
“The best comfort food will always be greens, cornbread, and fried chicken.”
- Maya Angelou, American poet and activist
Escherichia coli (E. coli) infections in general and E. coli urinary tract infections (UTIs) in particular have a profound impact on human health. In a recent study, researchers linked E. coli UTIs to eating poultry purchased from local grocery stores. If you have never had a UTI, you may wonder why you should care. In this Germ Gems post, I provide some background on E. coli and on UTIs in an attempt to answer why.
Different kinds of E. coli infections. E. coli is a bacterium that lives in the lower intestines of a large majority of humans and other warm-blooded animals. They are commensal microbes, living off nutrients in the gut but causing the host no harm. (It is a member of the healthy intestinal microbiome of over 90% of individuals.)
Humans most commonly acquire pathogenic E. coli from food animals, such as, undercooked beef. E. coli is perhaps best known as a cause of infections of the gastrointestinal (gi) tract such as traveler’s diarrhea— a gi infection that is more of a nuisance than a life-threatening disease. But shiga-toxin producing E. coli (STEC) and extraintestinal pathogenic Escherichia coli (ExPEC) are another matter—they’re highly pathogenic.
E. coli (STEC), causes bloody diarrhea and hemolytic uremic syndrome. Researchers have established undercooked beef as a common source of outbreaks of most STEC infections. On December 28, 2019, I wrote about STEC in my Germ Gem post “Escherichia coli 0157:H7 Lurking in Lettuce: Where’s the Beef?,” when three outbreaks of STEC were traced surprisingly to contaminated romaine lettuce rather than to undercooked beef.
ExPEC is the most common gram-negative bacterial pathogen in humans. It causes the vast majority of UTIs but is also a leading cause of bloodstream infection (bacteremia) in adults as well as being the second most common cause of meningitis in newborns.
Where do ExPEC come from? On February 28, 2023, researchers provided evidence that ExPEC can be acquired from an animal source, namely poultry. In a study published in One Health, “Using source--associated mobile genetic elements to identify zoonotic extraintestinal E. coli infections,” scientists isolated and sequenced E. coli strains collected from raw chicken, turkey, and pork from major grocery store chains in Flagstaff, Arizona. They then compared these data with those from urine and blood samples from patients hospitalized at Flagstaff Medical Center for UTIs. After analyzing the genomes, the researchers identified DNA in strains adapted to food animals and determined that about 8% of E. coli UTIs in the Flagstaff area could be linked to poultry.
From their data, the research team went on to estimate that between 480,000 and 640,000 UTIs in the U.S. each year may be caused by foodborne E. coli strains. In this study, the researchers also found that the foodborne E. coli infections were not only associated with UTIs but were also capable of causing serious bloodstream infections. While the main focus of the recent One Health study is on the newly confirmed recognition that ExPEC infections are in some cases zoonotic, the study also highlights the enormous impact of E. coli UTIs on human health.
The clinical importance of UTIs. UTIs can involve the upper urinary tract, that is, the kidneys, or the lower urinary tract (the bladder). Pyelonephritis (kidney infection) often precipitates hospitalization, whereas bladder infections (cystitis) are usually treated in the clinic. The clinical manifestations of both types of UTI are similar: burning or frequent urination; abdominal pain; fever; and vomiting.
According to a study reported in March 2022, UTIs cause more than 1 million emergency room visits and 100,000 hospitalizations per year in the U.S. Researchers estimated the cost of managing complicated (upper urinary tract) infections in emergency departments at over $3 billion per year.
In an article in Open Forum Infectious Diseases in January 2023, “Epidemiology, Clinical Features, and Antimicrobial Resistance of Invasive Escherichia coli Disease in Patients Admitted to Tertiary Care Hospitals,” researchers reported on the extraordinary clinical impact of ExPEC infections in hospitalized patients. They found that the case fatality rate from ExPEC infections was 20%, and of major concern, about two-thirds of E. coli isolates were resistant to one or more antibiotics—underscoring the problem that we are running out of antibiotics to treat serious infections. (In my September 30, 2019 Germ Gems post, “The Antibiotic Pipeline: Will It Dry Up?”, I reviewed the topic of the global crisis of antibiotic resistance. Since then, the problem has worsened.)
Prevention: “From Farm-to-Table.” The misuse and overuse of antibiotics causes antibiotic resistance. This means taking (or being prescribed) an antibiotic for a non-bacterial infection. But it also means using antibiotics in animal feed for growth promotion purposes.
Keeping animal feed free of antibiotics helps prevent emergence of antibiotic resistance. Fostered by consumer advocates, the U.S. Food and Drug Administration (FDA) and the Center for Disease Control and Prevention (CDC) have issued regulations that have resulted in major progress in eliminating the use of antibiotics in animal feed. But other measures are needed to prevent infections from meat that is colonized by ExPEC and STEC strains.
In a March 28, 2023 article in SciTechDaily, “Foodborne E. coli Menace: Bacteria From Meat Causes 480,000+ Urinary Tract Infections in the U.S. Every Year,” researchers from Northern Arizona University comment that producers and the FDA could do a better job of monitoring potentially dangerous pathogens in food, most notably raw meat sold in grocery stores throughout the country. These authors also suggest that consumers can limit their exposure to E. coli in contaminated food by taking steps such as washing their hands carefully when preparing or handling raw meat and using separate surfaces to prepare raw and cooked foods. Or to put it as succinctly as the CDC, the four steps to food safety are: “Clean, Separate, Cook, Chill.”