Bacterial Cystitis, Acute, Uncomplicated

PATHOGENS

• Distribution:

1. E. coli= 75-95%
2. S. saprophyticus= 0-2% in outpatients, much higher in young women

• Other organisms less common: other Enterobacteriaceae, P. aeruginosa, Group B and Group D Streptococci, and Enterococcus species.
• Rare pathogens: H.influenzae, M. tuberculosis, anaerobes, Salmonella, Shigella, adenovirus type 11, Ureaplasma, Mycoplasma.

• Uropathogenic E. coli (UPEC) = Subset of extraintestinal E. coli (ExPEC) most likely to cause UTIs are groups B2 and D that have "fitness elements" providing them with advantage in extraintestinal niche.
• Uncomplicated UTI: >95% of infections due to single organism.
• Factors favoring bacterial persistence/colonization and infection: (1) bacterial binding via fimbriae, (2) high growth rates despite high osmolarity and urea concentrations and low pH.
• Factors favoring bacterial elimination include: (1) high urine flow rate, (2) frequent voiding, (3) bactericidal effects of secreted proteins, (4) bladder mucosa and (5) inflammatory responses.