• The bacteria responsible for urinary tract infections are normally present in the bowel
  • Escherichia coli is the most common, accounting for 85 percent of community-acquired infections and up to 50 percent of nosocomial infections
  • Proteus sp., Klebsiella sp., Enterococcus faecalis, and Staphylococcus saprophyticus
  • The female urethra is short, and bacteria generally enter the bladder in an ascending fashion
  
  
• Host defense mechanisms
  • More important than bacterial virulence or inoculum size in determining whether a clinical infection develops.
  • Estrogens and pH affect attachment and colonization of the vaginal mucosa
  • Antiadherence properties of the vaginal and bladder mucosa
  • hydrokinetic clearance of bacteria through voiding
  • Changes in urine pH and composition that may inhibit bacterial growth
  
  
• Newly recognized intracellular bacterial biofilm-like pods on the bladder surface, resistant to normal host-defense mechanisms, may account for bacterial persistence in some patients prone to recurrent infection.
  
• Women with recurrent urinary tract infections demonstrate increased adherence of bacteria in vitro to uroepithelial cells when compared to findings in women who have never had an infection. Studies suggest that this may be genetically determined.
  
• Risk factors
  • Sexual intercourse
  • Use of a diaphragm or cervical cap
  • Spermacidal jelly
  • ABO-blood group nonsecretor phenotype
  • Urologic instrumentation
  • Diabetes
  • Age-related changes in the elderly patient
    • Low estrogen levels allow vaginal pH to rise, resulting in a higher likelihood of vaginal colonization with E. coli

References

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