Infectious_Disease_Lecture_1B_UTI (1)

Urinary Tract Infections (UTIs)

Introduction

  • UTIs are a common cause of morbidity, leading to significant healthcare demands.

  • Contrary to older beliefs, urine does not need to be sterile; it contains bacteria that play a role in the microbiome.

  • Disturbances in urinary flora can lead to urinary diseases.

Epidemiology

  • Annually, in the U.S.:

    • 9 million ambulatory visits

    • 2 million hospitalizations for community-acquired UTIs

    • 1 million intrahospital infections.

  • UTIs account for approximately 40% of healthcare-associated infections.

  • About half of women will experience a UTI by age 30.

Risk Factors

  • Major Risk Factors:

    • Sexual activity

    • Structural abnormalities

    • Various contraceptive methods (e.g., spermicides, diaphragms)

    • Pregnancy and diabetes

    • Catheterization and instrumentation

    • Incontinence and immunosuppression

    • Genetic predispositions

Types of UTIs

  • Anatomical Classification:

    • Cystitis: Lower urinary tract infection (bladder).

    • Pyelonephritis: Upper urinary tract infection (kidneys).

  • Classification by Complexity:

    • Uncomplicated UTIs: Affect non-pregnant women without structural/neurologic abnormalities.

    • Complicated UTIs: Includes infections in men, pregnant women, immunocompromised individuals, or those with structural anomalies.

Clinical Presentation

  • Cystitis Symptoms:

    • Dysuria (pain or burning sensation during urination)

    • Polyuria (frequent urination)

    • Urgency and suprapubic pain.

  • Pyelonephritis Symptoms:

    • Flank pain and fever.

Etiology

  • Common Pathogen:

    • E. Coli accounts for 75-95% of UTIs in women.

  • Other Pathogens:

    • Less common: Streptococcus, Enterococcus, Staphylococcus saprophyticus.

    • Healthcare-associated UTIs may involve complex pathogens such as Providencia, Morganella, and Proteus.

  • Pathogenic vs. Commensal Organisms:

    • Not all bacteria detected in urine are harmful; benign strains also exist.

Diagnosis

  • Urinalysis Criteria:

    • Presence of WBCs > 5 suggests infection.

    • Positive nitrites indicate infection by nitrate-reducing bacteria.

    • Alkaline pH typically indicates a UTI.

  • Valid Test Indicators:

    • Less than 5 WBCs indicate no infection.

    • High epithelial cells can indicate a dirty sample, which may negate culture results.

  • Quantitative Culture:

    • Required for diagnosis, especially with symptomatic patients, even under 100,000 CFU/mL.

Treatment

  • First-Line Agents:

    • Nitrofurantoin for cystitis is highly recommended due to low resistance.

    • Avoid Amoxicillin/Ampicillin due to resistance.

  • Duration of Therapy:

    • Generally 3-5 days for uncomplicated cystitis.

  • For Pyelonephritis:

    • Treatment may extend 7-14 days based on the antibiotic used.

Complications

  • Untreated UTIs may lead to:

    • Sepsis

    • Renal abscesses

    • Short-term recurrence and long-term renal damage (hypertension, end-stage renal disease).

Special Considerations

  • Asymptomatic Bacteriuria:

    • Not treated unless in pregnancy or invasive procedures.

    • Treatment concerns revolve around preventing antibiotic resistance.

UTI Management Summary

  • Avoid unnecessary testing and treatment in asymptomatic individuals.

  • Understand the differences in treatment for uncomplicated vs. complicated UTIs.

  • Choose appropriate empirical therapy based on the most common pathogens (primarily E. Coli).

  • Monitor for potential complications and ensure urine culture linked with clinical symptoms.