Background
- Bacterial infection of the urinary tract, either lower (cystitis) or upper (pyelonephritis)
- When UTI causes sepsis syndrome, often referred to as urosepsis
Microbiology
- Gram-negative bacteria
- Escherichia coli, most common cause overall
- Proteus, Klebsiella, Enterobacter
- Pseudomonas, Acinetobacter
- Gram-positive bacteria
- Staphylococcus saprophyticus, more common in young women
- Enterococcus faecalis
- Staphylococcus aureus, as a complication of Staphylococcus aureus bacteremia
- Corynebacterium urealyticum
- Viruses
- Adenovirus, which can cause hemorrhagic cystitis in hematopoietic stem cell transplantation recipients
- BK virus, in renal transplant recipients
Risk Factors
- Premenopausal women: sexual intercourse, new partner, no postcoital voiding, spermicide use, prior UTI, diabetes mellitus
- Postmenopausal women: genitourinary atrophy/estrogen deficiency, urethral diverticulum, vaginal prolapse beyond the hymen, incontinence, postvoid residual, catheterization
- Men: reduced prostatic secretions (older men), postvoid residual, incontinence, catheterization
Clinical Manifestations
- Acute simple cystitis: acute UTI without signs of upper tract infection or systemic symptoms
- Acute complicate UTI: acute UTI with fever, chills, malaise, flank pain, CVA tenderness, or (in men) pelvic/perineal pain
- Diagnostic criteria include clinical and laboratory symptoms:
- Two or more clinical symptoms:
- Fever > 38ºC
- Urinary urgency or frequency
- Acute dysuria
- Hypogastric pain
- Costovertebral angle tenderness
- One or more laboratory finding:
- Bacteriuria (> 100,000 CFUs/mL)
- Pyuria (>10 WBCs/HPF)
- Two or more clinical symptoms:
Investigations
- Urinalysis
- Leukocyte esterase
- Nitrite, positive for organisms that convert nitrate to nitrite such as the Gram-negative bacteria
- High negative predictive value if both LE and nitrite are negative
- Urine microscopy
- Pyuria indicated by 5-10 cells per HPF
Management
- Acute afebrile UTI in men: 7 days ciprofloxacin or cotrimoxazole1
- Acute afebrile UTI in women:
- First-line antibiotics
- Nitrofurantoin monohydrate/macrocrystals (Macrobid) 100 mg p.o. twice daily for 5 days
- Co-trimoxazole DS p.o. twice daily for 3 days
- Fosfomycin 3 g p.o. once
- Trimethoprim 100 mg p.o. twice daily for 3 days
- Pivmecillinam 400 mg p.o. three times daily for 3 to 5 days
- Second-line is a β-lactam
- Amoxicillin-clavulanic acid 500 mg/125 mg p.o. twice daily for 5 to 7 days
- Cefadroxil 500 mg p.o. twice daily for 5 to 7 days
- Cephalexin 250 to 500 mg p.o. every 6 hours for 5 to 7 days
- Last-line is a fluoroquinolone
- Ciprofloxacin 250 mg p.o. twice daily for 3 days
- Ciprofloxacin XR 500 mg p.o. daily for 3 days
- Levofloxacin 250 mg p.o. daily for 3 days
- First-line antibiotics
ESBLs
- Uncomplicated UTIs:
- Preferred: nitrofurantoin or co-trimoxazole
- Alternatives: amoxicillin-clavulanate (if in vitro susceptibility), single-dose aminoglycosides, and oral fosfomycin (for E. coli)
- Complicated UTIs and pyelonephritis:
- Preferred: ertapenem, meropenem, imipenem-cilastatin, ciprofloxacin, levofloxacin, or trimethoprim-sulfamethoxazole
- Alternatives: once-daily aminoglycosides
CREs
- Uncomplicated UTIs:
- Preferred: ciprofloxacin, levofloxacin, trimethoprim-sulfamethoxazole, nitrofurantoin, or a single-dose of an aminoglycoside
- Alternative: meropenem (if susceptible), ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, cefiderocol
- Also: single-dose aminoglycosides
- For CRE E. coli: fosfomycin
- If necessary: colistin
- Complicated UTIs and pyelonephritis:
- Preferred: ciprofloxacin, levofloxacin, and trimethoprim-sulfamethoxazole
- Alternative: extended-infusion meropenem (if susceptible), ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, cefiderocol
- Also: once-daily aminoglycosides
References
- ^ Dimitri M. Drekonja, Barbara Trautner, Carla Amundson, Michael Kuskowski, James R. Johnson. Effect of 7 vs 14 Days of Antibiotic Therapy on Resolution of Symptoms Among Afebrile Men With Urinary Tract Infection. JAMA. 2021;326(4):324. doi:10.1001/jama.2021.9899.