[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Enterobacterales](https://durgical.com/en/microbiology/groups/enterobacterales/) › Escherichia coli [Microbiology](https://durgical.com/en/microbiology/) · [Enterobacterales](https://durgical.com/en/microbiology/groups/enterobacterales/) # Escherichia coli - Bacterium - Gram-negative - Contact - Exam priority: high A normal gut bacterium. Some strains cause most urinary infections, plus diarrhea, newborn meningitis and sepsis. Updated 2026-11-01 Also called: E. coli ## Key points - Number one cause of urinary infection, in the community and in hospital. - Lactose fermenter: pink on MacConkey, metallic green on EMB. - EHEC O157:H7: no sorbitol fermentation, Shiga toxin, hemolytic uremic syndrome; antibiotics contraindicated. - ETEC: traveler's diarrhea from LT (cAMP) and ST (cGMP) toxins. - K1 capsule: neonatal meningitis, alongside group B streptococcus. ## At a glance **Gram** Gram-negative **Shape** Rod **Oxygen** Facultative anaerobe **Family** Enterobacteriaceae **Stain** Gram: red rods ## Morphology - Motile Gram-negative rod with flagella - Lactose fermenter: pink colonies on MacConkey and a green metallic sheen on EMB agar - Indole-positive, oxidase-negative - E. coli O157:H7 does not ferment sorbitol (colorless colonies on sorbitol-MacConkey) ## Transmission - Urinary infection: the person's own gut flora climbs from the perineum up the urethra - Diarrhea: water or food contaminated with feces; undercooked ground beef, raw milk and raw produce (EHEC) - Newborn: from maternal vaginal flora during birth - Contact (on top of standard) for diapered or incontinent patients with diarrhea **Reservoir:** Human and animal gut; Cattle: main reservoir of E. coli O157:H7 ### Isolation precautions What the care team adds to standard precautions. **Contact** Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing. ## Virulence factors - P fimbriae: attachment to upper urothelium, pyelonephritis - Type 1 fimbriae: bladder attachment, cystitis - K1 capsule: neonatal meningitis - ETEC: heat-labile toxin (raises cAMP) and heat-stable toxin (raises cGMP), watery traveler's diarrhea - EHEC: Shiga toxin stops protein synthesis (60S subunit), injures endothelium and causes hemolytic uremic syndrome - EIEC invades the mucosa (dysentery); EPEC attaches and effaces microvilli (infant diarrhea) - LPS: fever and septic shock ## Diseases it causes - Lower urinary tract infection (cystitis): the leading cause [Urinary tract infection (acute cystitis) →](https://durgical.com/en/conditions/urinary-tract-infection/) - Acute pyelonephritis [Acute pyelonephritis →](https://durgical.com/en/conditions/acute-pyelonephritis/) - Hemolytic uremic syndrome after bloody diarrhea from EHEC [Hemolytic uremic syndrome (HUS) →](https://durgical.com/en/conditions/hemolytic-uremic-syndrome/) - Neonatal sepsis [Neonatal sepsis →](https://durgical.com/en/conditions/neonatal-sepsis/) - Neonatal meningitis from K1 strains [Bacterial meningitis →](https://durgical.com/en/conditions/bacterial-meningitis/) - Acute gastroenteritis and traveler's diarrhea (ETEC) [Acute (viral) gastroenteritis →](https://durgical.com/en/conditions/acute-gastroenteritis/) ## Clinical picture - Dysuria, urgency and frequency; fever and flank pain if it reaches the kidney - Bloody diarrhea without high fever: think EHEC - Hemolytic anemia, low platelets and acute kidney injury a week later: hemolytic uremic syndrome ## Diagnosis - Urinalysis: positive nitrite and leukocyte esterase; urine culture with colony count - Stool culture on sorbitol-MacConkey and detection of Shiga toxin or its genes by PCR - Blood and CSF culture in newborns - Susceptibility testing: look for extended-spectrum beta-lactamases (ESBL) ## Treatment Lower urinary infection: nitrofurantoin or fosfomycin depending on local resistance; pyelonephritis and sepsis: third-generation cephalosporins or other beta-lactams; ESBL strains: carbapenems. Antibiotics are not used in EHEC diarrhea because they can raise the risk of hemolytic uremic syndrome. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Nitrofurantoin](https://durgical.com/en/pharmacology/nitrofurantoin/) - [Fosfomycin](https://durgical.com/en/pharmacology/fosfomycin/) - [Ceftriaxone](https://durgical.com/en/pharmacology/ceftriaxone/) - [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) - [Meropenem](https://durgical.com/en/pharmacology/meropenem/) ## Prevention - Cook ground beef through and use pasteurized milk - Handwashing and keeping raw and cooked food apart - Safe water - Early removal of urinary catheters ## In Colombia E. coli is the main cause of urinary infection in Colombia; acute diarrheal disease is an INS surveillance event, and ESBL production means treatment follows the local antibiogram. ## Memory aid "Read the letters": ETEC's T is for Toxins and Tourists, EHEC's H is for Hemorrhage and Hemolytic uremic, EIEC's I is for Invasion, EPEC's P is for Pediatric. ## Test yourself Think of the answer, then tap the question to see it. ## Which bacterium causes most urinary tract infections? Uropathogenic Escherichia coli. ## Why are antibiotics withheld in bloody diarrhea from E. coli O157:H7? They can increase Shiga toxin release and the risk of hemolytic uremic syndrome. ## Which medium separates E. coli O157:H7 from other strains? Sorbitol-MacConkey agar: O157:H7 does not ferment sorbitol and gives colorless colonies. ## Which E. coli virulence factor is linked to neonatal meningitis? The K1 capsule. ## How do the LT and ST toxins of enterotoxigenic E. coli work? LT raises cAMP and ST raises cGMP in the enterocyte; both drive water secretion and watery diarrhea. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/escherichia-coli/) ## Related - [Shigella](https://durgical.com/en/microbiology/shigella/) - [Klebsiella pneumoniae](https://durgical.com/en/microbiology/klebsiella-pneumoniae/) - [Proteus mirabilis](https://durgical.com/en/microbiology/proteus-mirabilis/) ## Related conditions - [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/) - [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/) - [Hemolytic uremic syndrome (HUS)](https://durgical.com/en/conditions/hemolytic-uremic-syndrome/) - [Neonatal sepsis](https://durgical.com/en/conditions/neonatal-sepsis/) - [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/) - [Acute (viral) gastroenteritis](https://durgical.com/en/conditions/acute-gastroenteritis/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. **Contact** Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing. **Droplet** Surgical mask within about a metre; single room. **Airborne** N95 respirator and a negative-pressure room. [← Back to the group: Enterobacterales](https://durgical.com/en/microbiology/groups/enterobacterales/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Escherichia coli Infections](https://www.msdmanuals.com/professional/infectious-diseases/gram-negative-bacilli/escherichia-coli-infections) (MSD Manual Professional Edition, 2026); [E. coli](https://www.who.int/news-room/fact-sheets/detail/e-coli) (WHO, 2018); [Urinary Tract Infections](https://medlineplus.gov/urinarytractinfections.html) (MedlinePlus, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/escherichia-coli/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/escherichia-coli/