American Board of Pathology (ABPath) Practice Test

Escherichia coli is the most common organism responsible for urinary tract infections (UTIs), accounting for approximately 80-90% of all cases. The reason for this prevalence lies in E. coli's anatomical location in the gastrointestinal tract, where it is found in large numbers. This proximity allows for easy transfer to the urinary tract, particularly in females, where the urethra is shorter and located close to the rectal area.

E. coli is well-adapted to adhere to the uroepithelial cells lining the urinary tract, a crucial factor for colonization and infection. It has various virulence factors, including fimbriae that enhance its ability to attach to the urinary tract, leading to the inflammation and symptoms associated with UTIs.

While other organisms listed, such as Staphylococcus saprophyticus, Proteus mirabilis, and Klebsiella pneumoniae, can cause UTIs, they are less common. Staphylococcus saprophyticus is known to cause UTIs primarily in sexually active young women, but it is not as prevalent as E. coli. Proteus mirabilis and Klebsiella pneumoniae are associated with UTIs in certain populations, especially those with underlying health conditions or catheterization