Escherichia coli infection refers to disease caused by pathogenic strains of a normally commensal gut bacterium, ranging from mild traveler's diarrhea to lethal hemolytic uremic syndrome. Six diarrheagenic pathotypes — STEC, ETEC, EPEC, EIEC, EAEC, and DAEC — produce distinct clinical syndromes through different virulence mechanisms.
Escherichia coli infection (ICD-10: A04.0-A04.4 for intestinal infections) covers disease caused by pathogenic strains of Escherichia coli, a Gram-negative facultative anaerobic bacterium that normally colonizes the human colon as a commensal. Pathogenic strains are categorized as either diarrheagenic (causing gastrointestinal disease) or extraintestinal pathogenic E. coli (ExPEC, causing UTI, sepsis, neonatal meningitis). Six diarrheagenic pathotypes are recognized: Shiga-toxin-producing E.
The key symptoms of Escherichia coli Infection are: Watery diarrhea starting 1-3 days after a high-risk meal or exposure — characteristic of ETEC traveler's diarrhea and EPEC; typically 4-10 stools per day with crampy abdominal pain., Bloody diarrhea starting 3-4 days after exposure to undercooked ground beef, leafy greens, or unpasteurized dairy — STEC pattern; often non-bloody initially then becoming hemorrhagic over 24-48 hours., Severe abdominal cramping and tenderness, particularly in the right lower quadrant in STEC infection — sometimes mistaken for appendicitis., Low-grade or absent fever in classic STEC — high fever points toward Salmonella, Shigella, or EIEC rather than STEC., Nausea, vomiting, and anorexia accompanying the diarrhea, particularly in children with STEC or ETEC., Dehydration symptoms — thirst, dry mouth, decreased urine output, lightheadedness, sunken eyes — particularly serious in infants and elderly., Dysuria, frequency, urgency, and suprapubic pain in UTI from uropathogenic E. coli (UPEC) — the dominant cause of community-acquired cystitis..
Diagnosing E. coli infection has been transformed by multiplex PCR stool panels, which simultaneously detect STEC (by Shiga toxin gene), enterotoxigenic E. coli (by LT/ST genes), enteropathogenic E. coli (by eae gene), enteroaggregative E. coli, and enteroinvasive E. coli pathotypes, along with other diarrheal pathogens. Stool culture remains essential for STEC public health surveillance, serotyping, and antibiotic susceptibility. Traditional sorbitol-MacConkey agar culture identifies E. coli O157:H7 by its inability to ferment sorbitol — a feature unique among common E. coli. Non-O157 STEC require Shiga toxin assay or PCR for detection because they ferment sorbitol normally. CDC and IDSA recommendations call for stool Shiga toxin testing in any patient with acute bloody diarrhea, regardless of whether STEC is suspected clinically. Serotyping and whole-genome sequencing of STEC isolates support outbreak investigation. For complicated STEC infection, additional testing includes complete blood count and blood film (looking for schistocytes), LDH (elevated in microangiopathic hemolysis), reticulocyte count, coagulation studies, electrolytes, urea, creatinine, and urinalysis. The CDC defines HUS as the simultaneous occurrence of microangiopathic hemolytic anemia, thrombocytopenia under 150,000, and acute kidney injury (creatinine elevation, oliguria, or hematuria/proteinuria) within 3 weeks of bloody diarrhea. UTI diagnosis combines symptoms with urinalysis (pyuria, nitrites) and urine culture; for uncomplicated cystitis in young women with classic symptoms, empirical treatment without culture is acceptable. Pyelonephritis, complicated UTI, recurrent UTI, and hospital-onset UTI require culture and sensitivity testing. Blood cultures are obtained in suspected sepsis or pyelonephritis.
Most E. coli infections resolve completely with supportive care or appropriate antibiotics. Uncomplicated UTIs cure in 88-94% with first-line therapy; ETEC traveler's diarrhea resolves in 3-5 days with empirical antibiotics. STEC infection without HUS resolves in 5-10 days. The major prognostic story centers on STEC-associated hemolytic uremic syndrome: acute mortality is 3-5% in pediatric HUS and up to 20% in elderly HUS, with most deaths from cardiovascular, neurological, or pulmonary complications during the acute phase. Among children who survive acute HUS, approximately 70% recover renal function fully; 20-30% develop long-term proteinuria, hypertension, or chronic kidney disease, and 3-5% progress to end-stage renal disease requiring dialysis or transplant within 10 years. Long-term neurological sequelae (seizures, behavioral changes) occur in 5-10% of severe HUS survivors. Adult HUS is less common but carries worse mortality. UTI from uropathogenic E. coli has excellent prognosis with appropriate antibiotics, though recurrence rates exceed 25% in women within 6 months of an initial UTI. Multidrug resistance — particularly ESBL and carbapenem-resistant E. coli — is an increasingly important determinant of outcome, with limited treatment options and higher mortality in resistant infections.
Refer to infectious disease, gastroenterology, or pediatric nephrology for suspected STEC infection requiring HUS monitoring, persistent diarrhea over 14 days, recurrent UTI, multidrug-resistant E. coli, complicated pyelonephritis, immunocompromised patients with severe infection, or outbreak investigation. Most uncomplicated cases are managed in primary care or emergency departments.
Find specialists →ETEC traveler's diarrhea: 3-5 days with antibiotics, 5-7 days without. STEC infection: 5-10 days of diarrhea; HUS, if it develops, declares itself within days 5-14 of illness and requires hospital care for 2-6 weeks. Uncomplicated UTI: symptom relief within 24-48 hours of starting effective antibiotics. Pyelonephritis: 7-14 days for full clinical recovery; recheck urine culture 1-2 weeks after treatment completion. Recovery from HUS-associated acute kidney injury takes weeks to months; long-term renal monitoring is required.
Rest during acute diarrheal illness and for 24-48 hours after symptom resolution. Vigorous exercise during dehydration is hazardous. Light activity may resume as fluid intake catches up with losses. Recovery from severe HUS may require weeks to months before return to normal physical activity.
For suspected STEC, prioritize centers with rapid molecular stool diagnostics and pediatric nephrology access. For recurrent UTI, urology or infectious disease consultation is helpful when standard prevention fails. Travel medicine clinics provide pre-travel counseling and self-treatment plans for ETEC. Look for systems with established care pathways for multidrug-resistant organisms.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
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