by Dr. Jaclynn Moskow
Escherichia coli (E. coli) is a species of Gram-negative, rod-shaped, facultatively anaerobic bacteria. Many E. coli strains are a part of the normal flora of the gut microbiome. E. coli can also be found in the normal flora of the skin and genital tract (1).
Strains of E. coli that are part of the microbiome can be pathogenic under certain conditions – often when introduced to a new part of the body. Additionally, strains of E. coli that are not normally found in the microbiome can also cause significant disease (i.e., enterovirulent E. coli).
E. coli is the most common cause of urinary tract infection and biliary sepsis, and a common agent in travelers’ diarrhea, foodborne gastroenteritis, hemorrhagic colitis, and a wide variety of systemic infections (2).
Enterotoxigenic Escherichia Coli (ETEC)
Enterotoxigenic E. coli (ETEC) infection is the most common cause of diarrhea in children (4) and the leading cause of travelers’ diarrhea (5). It is transmitted via contaminated food and water. Symptoms commonly include watery diarrhea and abdominal cramping. Most cases are self-limited, but infection may be life-threatening in infants.
Enteropathogenic Escherichia Coli (EPEC)
Enteropathogenic E. coli (EPEC) infection is a common cause of infantile diarrhea, although it can affect people of all ages. Like ETEC, diarrhea caused by EPEC infection is usually watery. The organism is also spread via the fecal-oral route, commonly via contaminated food and water. Infection is usually self-limited.
Uropathogenic E. Coli (UPEC)
E. coli strains that cause urinary tract infection are referred to as uropathogenic E. coli (UPEC). Individuals at increased risk of UPEC infection include neonates, sexually active women, geriatric individuals, and patients with indwelling urinary catheters.
Approximately 40% of adult women will experience cystitis at some point, with UPEC identified as the causative agent in 75-80% of cases (3). Untreated cystitis caused by UPEC infection can progress to pyelonephritis. Symptoms of cystitis/pyelonephritis may include dysuria, hematuria, increased urinary frequency, cloudy or foul-smelling urine, flank pain, vomiting, and fever.
Many different antibiotics are commonly used to treat UPEC infections, including penicillins, cephalosporins, fluoroquinolones, and trimethoprim-sulfamethoxazole. Treatment may be complicated by the increasing prevalence of antibiotic-resistant strains.
Shiga Toxin-Producing E. Coli (STEC)
Shiga toxin-producing E. coli (STEC) is also referred to as Verocytotoxin-producing E. coli (VTEC) or Enterohemorrhagic E. coli (EHEC). This variety of E. coli is most commonly associated with foodborne outbreaks in the developed world. Infection can be acquired from contaminated bovine meat, milk and dairy products, vegetables, fruit, and water (6).
Unlike ETEC and EPEC, infection with STEC usually causes bloody diarrhea. Treatment of diarrhea from STEC is supportive and includes fluid replacement. Infection with STEC can also cause hemolytic-uremic syndrome (HUS), most notably associated with E. coli O157:H7 strain. Nearly 40% of patients with STEC-HUS require temporary renal replacement therapy, and up to 20% will have permanent residual kidney dysfunction (2).
Worldwide, it is estimated that STEC infection causes approximately 2.8 million acute illnesses annually, 3900 cases of HUS, 270 cases of end-stage renal disease, and 230 deaths (7).
In 1993, E. coli O157:H7 made headlines when an outbreak occurred at the Jack-in-the-Box restaurant chain in the United States, affecting a total of 73 restaurant locations across 4 states. The source of this outbreak was determined to be contaminated hamburger patties. More than 700 people became ill, including 171 hospitalizations and four deaths (8). More recently, in 2019, the CDC issued a warning to avoid Romaine lettuce from the Salinas Valley region in California (9). They reported that E. coli O157:H7 infection from this vegetable affected 167 people across 27 states, with 85 hospitalizations, and 15 cases of the hemolytic uremic syndrome (10).
United States. E. coli – VTEC infection, cases and rates per 100,000
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Enteroaggregative E. Coli (EAEC)
Enteroaggregative E. coli (EAEC) infection is recognized as the second most common cause of traveler’s diarrhea (10). It can also cause both acute and chronic childhood diarrhea. EAEC infection has been associated with reduced growth acceleration and failure to thrive among children in developing countries (11). EAEC are also the strains most commonly associated with diarrhea among individuals with HIV/AIDS (12). Diarrhea caused by EAEC is usually watery in nature. In some cases, infection is self-limiting, while in other cases, antibiotics are warranted. Fluoroquinolones, especially ciprofloxacin, are widely considered the treatments of choice (13).
Enteroinvasive E. Coli (EIEC)
Enteroinvasive E. coli (EIEC) are strains that possess some of the biochemical characteristics of E. coli and have the ability to cause dysentery through an invasion mechanism similar to that of Shigella (14). As in shigellosis, diarrhea caused by EIEC may be watery or bloody, and mucus is sometimes present. Infection is usually self-limiting.
Diffusely Adherent E. Coli (DAEC)
Diffusely-adherent E. coli (DAEC) is the most recent diarrheagenic E. coli pathogroup to be identified. DAEC infection is associated with diarrhea in children, where the risk of infection increases with age. These organisms have also been identified as agents of diarrhea in travelers and in patients with HIV/AIDS. Strains have also been isolated from patients with inflammatory bowel disease and colorectal cancer (15).
Meningitis/Sepsis-Associated E. Coli (MNEC)
Meningitis/Sepsis-Associated E. coli (MNEC) infection is a common cause of severe disease in neonates. MNEC infection has a case fatality rate of 15–40% and may result in severe neurological defects in survivors (16). Third-generation cephalosporins are the recommended treatments for neonatal MNEC infection (17). Rarely, MNEC infection occurs in adults, particularly in those who are immunocompromised.
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(6) “Pathogenicity assessment of Shiga toxin‐producing Escherichia coli (STEC) and the public health risk posed by contamination of food with STEC”, European Food Safety Authority, 2020. [Online]. Available: https://www.efsa.europa.eu/en/efsajournal/pub/5967
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(8) “Jack in the Box E. Coli Outbreak – 25 Years Later”, Canadian Institute of Food Safety, 2021. [Online]. Available: https://www.foodsafety.ca/news/jack-box-e-coli-outbreak-25-years-later
(9) “The Final Update on the Multistate Outbreak of E. coli 0157:H7 Infections”, Centers for Disease Control and Prevention, 2020. [Online]. Available: https://www.cdc.gov/media/releases/2020/s0115-ecoli-outbreak.html
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