Pathophysiology

The vast majority of UTIs arise from bacteria ascending the urinary tract. Women, because of the shorter distance from the urethra to bladder, proximity of the vagina and rectal area, are more prone to them. Men tend to develop UTIs in conjunction with prostatic hypertrophy (majority), renal stones, catheterisation, recent cystoscopy and anal intercourse.

In the majority of patients (between 75-95%) with uncomplicated cystitis and pyelonephritis, the infection is monobacterial with Escherichia coli [2]. Staphylococcus saprophyticus is isolated in 5-15%, enterococci, klebsiella and proteus account for the remaining 5-10%. It is important to note that the virulence of the infecting organism is less important than host factors in complicated infections [3].

E.coli remains the dominant pathogen in complicated UTIs. However, patients at risk from complicated UTIs are more likely to culture less common antibiotic resistant organisms. The choice of empiric antibiotic employed in these patients must take this into account.