CHAPTER 75: Urinary Tract Infections

KEY POINTS

• Empiric antimicrobial therapy for acute severe urosepsis should initially include two agents with activity against gram-negative bacilli, such as a third- or fourth-generation cephalosporin, aztreonam, or extended-spectrum penicillin in combination with either a fluoroquinolone or an aminoglycoside.

• Where local epidemiology indicates significant prevalence of extended-spectrum ß-lactamases among Enterobacteriaceae, then a carbapenem such as imipenem, meropenem, ertapenem, or doripenem is preferred while awaiting definitive cultures.

• Where local epidemiology indicates significant prevalence of carbapenem-resistant Enterobacteriaceae, then colistin and a carbapenem should be chosen while awaiting definitive cultures.

• Urine and blood cultures should be obtained prior to the first antimicrobial doses, which should be given without delay.

• Once the pathogen is identified by a positive urine or blood culture, the antimicrobial regimen should be tailored to a single, least toxic agent with the narrowest spectrum, based on susceptibility data.

• Patients with severe urosepsis requiring ICU admission should have imaging of the urinary tract on an urgent basis, preferably by computed tomography with intravenous contrast, because suppurative complications require drainage as a priority.

• Percutaneous drainage by an interventional radiologist is generally preferred to drain definitively or stabilize temporarily a patient with suppurative complications.

• Urinary catheters cause a high incidence (3%-7% per day) of bacteriuria and candiduria; the latter associated with broad-spectrum antimicrobial therapy.

• Asymptomatic catheter–associated bacteriuria or candiduria should not be treated; the only exceptions are transplant and neutropenic patients, and before instrumentation of the urinary tract.

• The continued usefulness of a urinary catheter should be reassessed on a regular basis, and removal in selected patients should be considered.

• Fever or sepsis should only be attributed to catheter-associated bacteriuria and treated only after exclusion of other potential causes of infection.

Community-acquired pyelonephritis sometimes leads to sepsis syndrome and intensive care unit (ICU) admission, especially when it arises in an obstructed urinary tract or when the host defense is compromised by poorly controlled diabetes. Bacteremia arises in about 15% of cases, at a rate of 50 per 100,000 person years, with a 28-day mortality of about 5%.¹ Urinary tract infection (UTI) is also a common sequel of ICU, because of the use of urinary catheters for in excess of 70% of ICU patient days² and ranks in the top three or four of ICU-acquired infections.^3,4 Although older data suggested that catheter-associated UTI caused mortality,^5,6 more recent studies that control for confounding factors show no such link.^7-10 In addition the evidence that bacteriuria prolongs ICU stay or increases cost has also been challenged.¹¹ Unfortunately asymptomatic bacteriuria is frequently screened for and treated, resulting in harmful and unnecessary antimicrobial therapy.

Quantitative culture methods distinguish true bacterial multiplication within the urinary tract from a false result due to procurement contamination. Significant bacteriuria is defined as ≥10⁵ organisms/mL. In the presence of urinary symptoms, a count of ≥10² organisms/mL from a woman with pyuria represents true infection.¹² In a catheterized ...