The clinical presentation depends in large part on the site of the body infected by ExPEC.

• UTI: The urinary tract is the site most frequently infected by ExPEC; see Chap. 144. Urinary Tract Infections and Interstitial Cystitis for more details. E. coli causes 80-90% of ~6-8 million episodes of acute uncomplicated UTI in premenopausal women.
• Abdominal and pelvic infection: The abdomen and pelvis represent the second most common site of infection by ExPEC, which may be isolated in the setting of a polymicrobial infection; see Chap. 81. Intraabdominal Infections for more details. Syndromes include peritonitis, intraabdominal abscesses, and cholangitis.
• Pneumonia: ExPEC is generally the third or fourth most commonly isolated GNB in hospital-acquired pneumonia and can be a common cause of pneumonia in pts residing in long-term-care facilities; see Chap. 132. Pneumonia, Bronchiectasis, and Lung Abscess for more details.
• Meningitis:E. coli is one of the two leading causes of neonatal meningitis (the other being group B Streptococcus). Strains with the K1 capsular serotype are generally involved.
• Cellulitis/musculoskeletal infection:E. coli often contributes to infection of decubitus ulcers and diabetic lower-extremity ulcers, cellulitis, and burn-site or surgical-site infections. Hematogenously acquired osteomyelitis, particularly vertebral, is more commonly caused by E. coli than is generally appreciated. See Chap. 84. Infections of the Skin, Soft Tissues, Joints, and Bones for more details.
• Bacteremia:E. coli is one of the two most common blood isolates of clinical significance. E. coli bacteremia can arise from primary infection at any site, but originates most commonly from the urinary tract (50-67% of episodes) and next most commonly from the abdomen (25% of episodes). E. coli bacteremia is typically associated with sepsis. Endovascular infections are rare but have been described.