A 72-year-old man is brought to the emergency department from a skilled nursing facility due to altered mental status, skin flushing, and high fever. He uses a wheelchair for mobility since a stroke several years ago. Temperature is 38.9 C (102 F), blood pressure is 80/40 mm Hg, pulse is 120/min, and respirations are 26/min. A blood sample is obtained, and culture is positive for bacterial growth within a few hours. Multiplex PCR testing of the blood detects Escherichia coli. Which of the following is the most likely source of bacteremia in this patient?
This elderly patient with fever, hypotension, and altered mental status has sepsis. The presence of Escherichia coli bacteremia suggests the source is a urinary tract infection (UTI). E coli is a normal gastrointestinal commensal organism. UTI arises when the organism contaminates the periurethral area and uses special adhesive proteins called pili to attach to and ascend the uroepithelium. Predisposing factors include urinary obstruction (eg, benign prostatic hypertrophy), fecal incontinence, neurogenic bladder (eg, due to diabetes), and indwelling catheterization.
E coli is the leading cause of UTIs, and most cases of E coli bacteremia are due to hematologic dissemination from the urinary system. Bloodstream infection can lead to sepsis due to overwhelming release of inflammatory cytokines; clinical manifestations include hyper/hypothermia, tachycardia, tachypnea, leukocytosis, and organ dysfunction (eg, confusion, acute kidney failure).
(Choice A) Diverticulitis can cause E coli bacteremia due to spread of the organism through the colon wall. However, patients usually experience constant, worsening abdominal pain over several days. This patient is more likely to have a UTI, which frequently causes abrupt mental status changes in elderly patients.
(Choice B) Intestinal perforation can occur as a consequence of surgery, trauma, or wall rupture from ischemia; it often causes septic shock and anaerobic or gram-negative rod bacteremia. This patient is less likely to have intestinal perforation than a UTI.
(Choice C) Patients with a history of stroke are at risk for pneumonia due to aspiration. However, E coli is an atypical cause of pneumonia in those who are not intubated.
(Choice D) Wheelchair use may increase risk of pressure ulcers. Although E coli can contaminate a pressure ulcer, most skin infections are caused by gram-positive organisms (eg, Staphylococcus aureus, Streptococcus species). This patient is far more likely to have E coli bacteremia due to a UTI.
Educational objective:
Escherichia coli is the most common cause of urinary tract infection (UTI) in both healthy adults and elderly patients. E coli is part of the normal gastrointestinal flora, and special adhesive proteins (pili) allow some strains to colonize and ascend the urinary tract, causing UTI, pyelonephritis, and bacteremia/sepsis. UTIs are the most common cause of E coli bacteremia.