What do we know about the urinary tract infection-prone individual?

Abstract

Host factors play a pivotal role in the balance between sterility and infection of the urinary tact. Bacteria enter the urinary tract from the fecal reservoir via ascent thorough the urethra into the bladder. Most episodes of pyelonephritis are caused by retrograde ascent of bacteria from the bladder through the ureter to the renal pelvis and parenchyma. Unobstructed flow of urine and washout of transient urothelial colonizers is an integral part of the host defense. Other host defenses include the antibacterial effect of urine; glycoproteins that block adherence of bacteria to the urothelial and vaginal mucosa; and immunologic responses, including immunoglobulins, leukocytes, and cytokines, that facilitate bacterial clearance. The extent of susceptibility to urinary tract infection (UTI) is governed by bacterial virulence factors and the magnitude of deficiencies in host defense (figure 1). Complicated infections are associated with anatomic, functional, or metabolic abnormalities of the urinary tract that disable the natural defenses and lead to significant destruction of renal tissue. Uncomplicated infections are associated with more subtle, variable alterations governed by genetic, biologic, and behavioral or environmental factors that promote bacterial access to and colonization/infection of the urinary tract.