Escherichia coli infection
Escherichia coli is a gram-negative bacillus that causes most urinary tract infections and catheter-associated bloodstream infections, plus distinct diarrheagenic syndromes including travelers' diarrhea (ETEC) and hemorrhagic colitis with hemolytic uremic syndrome (EHEC/STEC). Diagnosis rests on culture with syndrome-specific colony-count thresholds, and management ranges from short-course oral antibiotics for cystitis to strictly supportive, antibiotic-avoiding care for EHEC.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Escherichia coli is a gram-negative bacillus and normal bowel commensal whose specific virulence-factor strains cause distinct human infections: uropathogenic strains cause most urinary tract…
- Epidemiology
Uropathogenic E. coli causes 75% to 95% of urinary tract infections in women, from ascending spread of the patient's own bowel flora.
- Risk factors
Female sex and sexual activity are the leading risk factors for cystitis and pyelonephritis.
- Pathophysiology
Uropathogenic strains express adhesins (type 1 and P fimbriae) that let the organism ascend from the bowel, colonize the periurethral area, and adhere to uroepithelial cells, initiating cystitis and, if unchecked, ascending pyelonephritis.
- Clinical features
Dysuria, urinary frequency and urgency, and suprapubic discomfort define uncomplicated cystitis, the most common presentation, typically without fever.
- Differential diagnosis
Klebsiella pneumoniae urinary tract infection: a clinical picture indistinguishable from E.
- Diagnosis
E. coli infection is confirmed by culture, with the diagnostic threshold defined by syndrome: uncomplicated cystitis is diagnosed clinically without routine culture; complicated cystitis…
- Management
First, for uncomplicated cystitis, treat with a first-line oral agent for a short course: nitrofurantoin 100 mg PO twice daily for 5 days trimethoprim-sulfamethoxazole 160/800 mg PO twice daily for 3…
- Complications
Hemolytic uremic syndrome (microangiopathic hemolytic anemia, thrombocytopenia, acute kidney injury) develops in less than 10% of EHEC/STEC infections and is the most serious diarrheal complication.
- Prognosis
Uncomplicated cystitis resolves in most patients within 1 week even without treatment, though treatment shortens symptoms and reduces ascending infection.
- Prevention
Avoid unnecessary urinary catheterization and remove an indwelling catheter as soon as it is no longer needed, since catheter duration is the primary modifiable CAUTI risk factor and removal at or…
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Bacteremia
Bacteremia is the presence of viable bacteria in the blood, confirmed by positive blood cultures, that ranges from transient and clinically silent to the trigger for sepsis and septic shock requiring urgent source identification and antimicrobial therapy.
- Candida infections
Candida species cause a spectrum from mucocutaneous disease (thrush, esophagitis, vulvovaginal candidiasis, intertrigo) to candidemia and invasive candidiasis, the fourth most common cause of bloodstream infection with 30-40% mortality. Diagnosis of invasive disease requires recognizing risk factors because only 40-60% of infected patients have positive blood cultures, and initial therapy is an echinocandin with prompt catheter removal.
- Pseudomonas aeruginosa infection
Pseudomonas aeruginosa is a nosocomial, opportunistic gram-negative bacillus that causes hot-tub folliculitis, malignant otitis externa, ventilator-associated pneumonia, febrile-neutropenia bacteremia with ecthyma gangrenosum, and device-associated infections. Empiric therapy requires an antipseudomonal agent and, in resistance-risk or unstable patients, double coverage until susceptibilities return.