Pathogens

 • Escherichia coli is the main organism.

• Staphylococcus saprophyticus and Proteus mirabilis are other causes.

 Epidemiology

 • extremely common. • ~60% of women will have a UTI at some point in their life.

Transmission

 • ascending spread of endogenous gut bacteria into the urethra.

 • The shorter urethra of women and its closer proximity to the anus are thought to be the main reason why females are more susceptible.

 Risk factors

 • Female gender, sexual intercourse, pregnancy, diabetes, catheterization, urinary tract obstruction, or malformation.

Pathogenesis

 • Pathogenic strains of E. coli have pili which allow them to bind to galactose- containing receptors on the surface of urothelial cells.

• Other important virulence factors include haemolysin which allows invasion of tissues and the K antigen which protects the organism from neutrophil phagocytosis.

Presentation

• Bladder infection (cystitis) causes frequency, urgency, dysuria, haematuria, and suprapubic pain.

 • ascending spread into the kidneys (acute pyelonephritis) causes a more severe illness with fever, rigors, vomiting, and loin pain.

 * May present with acute confusion in the elderly.

Diagnosis

• Urinalysis showing leucocytes or nitrites is a useful quick screening test.

• The gold standard is microbiological culture of a correctly collected midstream urine specimen. a pure growth of >105 organisms/ ml of urine is considered diagnostic.