Urinary tract infections host defenses

When bacteria overcome the cutaneous or mucosal barriers and penetrate body tissues, a bacterial infection is present Frequently the body succeeds in removing the invaders, without outward signs of disease, by mounting an immune response. If bacteria multiply faster than the body s defenses can destroy them, infectious disease develops with inflammatory signs, e.g., purulent wound infection or urinary tract infectioa Appropriate treatment employs substances that injure bacteria and thereby prevent their further multiplication, without harming cells of the host organism (1). 

Several age-related changes contribute to the high incidence of infections in geriatric patients. There appears to be a reduction in host defenses in the elderly, manifested in the increase in both serious infections and cancer. This may reflect an alteration in T-lymphocyte function. In the lungs, a major age and tobacco-dependent decrease in mucociliary clearance significantly increases susceptibility to infection. In the urinary tract, the incidence of serious infection is greatly increased by urinary retention and catheterization in men. 

After bacteria reach the urinary tract, three factors determine the development of infection the size of the inoculum, the virulence of the microorganism, and the competency of the natural host defense mechanisms. Most UTIs reflect a failure in host defense mechanisms. 

---