Infectious_Disease_Lecture_1B_UTI

Urinary Tract Infections (UTIs)

Overview

  • UTIs are common, with approximately 9 million outpatient visits and 2 million hospitalizations in the U.S. annually.

  • Community-acquired UTIs lead to 40% of all healthcare-associated infections.

  • Understanding the role of urinary microbiome: urine is not sterile and has both commensal and pathogenic bacteria.

Epidemiology and Risk Factors

  • Half of women experience a UTI by age 30.

  • Key risk factors include:

    • Sexual activity

    • Structural abnormalities of the urinary tract

    • Use of contraceptives (spermicides, diaphragms)

    • Pregnancy

    • Diabetes

    • Obesity

    • Catheterization

    • Immunosuppression

Classification of UTIs

  • Cystitis: Infections of the bladder, lower urinary tract.

  • Pyelonephritis: Infections of the kidneys and ureters.

Severity Classification

  1. Uncomplicated UTIs: Typically in non-pregnant women without existing urinary tract anomalies or serious comorbidities.

  2. Complicated UTIs: Occurs in men, pregnant women, or those with comorbidities or structural abnormalities.

Symptoms of UTIs

  • Cystitis symptoms include:

    • Dysuria (painful urination)

    • Polyuria (frequent urination)

    • Urgency

    • Suprapubic pain

  • Pyelonephritis symptoms include:

    • Flank pain

    • Fever

Common Pathogens

  • Majority caused by E. coli (75-95% of cases in women).

  • Less common pathogens include:

    • Other Enterobacteriaceae (Klebsiella, Proteus)

    • Streptococcus agalactiae (Group B Strep)

    • Staphylococcus saprophyticus

  • In healthcare settings, additional pathogens may include:

    • Pseudomonas, Proteus, Morganella, and Serratia.

Pathogenic Mechanisms

  • Commensal strains of E. coli do not provoke infection, while pathogenic strains have adhesins and can ascend to the kidneys, leading to severe infections.

  • Avoid unnecessary treatment of asymptomatic bacteriuria to prevent the emergence of more aggressive pathogens.

Urinalysis for UTI Diagnosis

  • Key components to review:

    • Leukocytes: >5 WBCs suggest infection.

    • Nitrates: Suggest presence of nitrate-reducing bacteria (e.g., E. coli).

    • Leukocyte esterase: An enzyme indicating WBC presence related to infection.

  • Valid tests should not have elevated epithelial cells; if present, repeat the test.

Empirical Treatment

  • First-line treatment for cystitis:

    • Nitrofurantoin: Effective, low resistance, minimal impact on normal flora.

  • Alternatives include:

    • Bactrim: Requires caution due to resistance.

    • Levofloxacin: Broad-spectrum, not preferred as first-line due to rising resistance.

  • Duration of treatment:

    • Typically 5 days for cystitis.

Complications of Untreated UTIs

  • Short-term:

    • Renal abscesses

    • Recurrence of UTIs

  • Long-term:

    • Hypertension

    • End-stage renal disease

    • Sepsis and systemic illness may occur.

Pyelonephritis Management

  • Requires urine culture and susceptibility testing for tailored therapy.

  • Aggressive symptoms include:

    • Fever, flank pain, potential septic presentation.

  • Duration of treatment may range from 7 to 14 days based on the pathogen and response.

Diagnosis Considerations

  • Avoid treating in asymptomatic bacteriuria unless in specific populations (e.g., pregnant women, invasive procedures).

  • A valid diagnosis requires a combination of symptoms, pyuria, and significant bacterial counts (100,000 CFU or more).

Conclusion

  • Prompt diagnosis and appropriate treatment are crucial to prevent complications from UTIs. Understanding the balance of urinary flora is key in managing and treating infections.