Urinary Tract Infection: Pathophysiology and Treatment

UTIs occur when pathogenic microorganisms colonize and infect the urinary tract, typically starting in the urethra and ascending to other parts of the urinary system, such as the bladder (cystitis) or kidneys (pyelonephritis).

• Primary Causes:
  • Escherichia coli (80–90%)
  • Other pathogens: Proteus mirabilis, Klebsiella pneumoniae, Staphylococcus saprophyticus
• Risk Factors: Catheterization, sexual activity, diabetes, obstruction, immune suppression.
• Pathogenesis:
  • Colonization occurs at the periurethral area and ascends to the bladder.
  • Epithelial damage, inflammation, and cytokine release contribute to symptoms.
  • Severe cases involve ascending infection to the kidneys or hematogenous spread.

• Antibiotics:
  • Beta-lactams (e.g., amoxicillin, ceftriaxone)
  • Fluoroquinolones (e.g., ciprofloxacin, levofloxacin)
  • Sulfonamides (e.g., sulfamethoxazole-trimethoprim)
  • Nitrofurans (e.g., nitrofurantoin)
  • Fosfomycin
• Analgesics: Phenazopyridine (for symptomatic relief)

• Beta-lactams: Inhibit bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to cell lysis.
• Fluoroquinolones: Inhibit bacterial DNA gyrase and topoisomerase IV, preventing DNA replication.
• Sulfonamides: Block folic acid synthesis by inhibiting dihydropteroate synthase, essential for bacterial DNA and RNA production.
• Nitrofurantoin: Reduced by bacterial enzymes to active intermediates that damage bacterial DNA, proteins, and cell walls.
• Fosfomycin: Inhibits enolpyruvyl transferase, blocking cell wall synthesis.

• Beta-lactams: Allergic reactions (rash, anaphylaxis), gastrointestinal disturbances (diarrhea, nausea).
• Fluoroquinolones: Tendonitis, QT prolongation, central nervous system effects (dizziness, confusion).
• Sulfonamides: Hypersensitivity reactions (rash, Stevens-Johnson syndrome), hemolysis in G6PD deficiency.
• Nitrofurantoin: Pulmonary toxicity (fibrosis), hepatotoxicity, gastrointestinal upset.
• Fosfomycin: Diarrhea, headache, and occasionally allergic reactions.