These organisms (for example, bacteria such as E. coli or Pseudomonas) infect the urinary tract by relocating against the flow of urine (retrograde) toward the kidneys. Lower urinary tract infections do not involve the kidneys while upper urinary tract infections involve the kidneys and are typically more severe. These types of infections of the urinary tract are almost never contagious to other individuals. This article will not consider STDs and the organisms that cause STDs as urinary tract infections as they are discussed in other articles.