Escherichia coli is by far the most frequent cause of uncomplicated community-acquired UTIs. At the molecular level, the E. coli that causes UTTs is sufficiendy different from other types of E. coli so as to be designated uropathogenic E. coli (UPEC). Other bacteria frequently isolated from patients with UTTs are Klebsiella spp., other Enterobaderiaceae, Staphylococcus saprophytics, and en-terococd In more complicated UTTs, particularly in recurrent infections, the relative frequency of infection caused by Proteus, Pseudomonas, Klebsiella, and Entero-bacter spp. increases.
Upper urinary tract
Lower urinary tract
Figure 57-1 Overview of the anatomy of ihe urinary tract (From Potter PH, Perry AG: Fundamentals of nursing, St Louis, 1985, Mosby.)
BOX 57-1 Resident Microflora of the Urethra
Coagulase-negatlve staphylococci (excluding S. saprophytics)
Virldans and non-hemolytic streptococci
Diphtheroids (Corynebacterium spp.) Nonpathogenic (saprobic) Neisseria spp. Anaerobic cocci Propionibacterium spp. Anaerobic gram-negative bacilli Commensal Mycobacterium spp. Commensal Mycoplasma spp.
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