This patient presents with a urinary tract infection (UTI), most likely caused by E. coli. The P fimbriae virulence factor of E. coli enables binding to uroepithelial cells and allows for cystitis and pyelonephritis.
UTIs are infections affecting the lower or upper urinary tract. They are often referred to as "honeymoon cystitis" due to their association with increased sexual activity. Common symptoms of lower UTIs include increased frequency, dysuria, and increased urge. E. coli is the most common cause of UTIs, followed, in order, by Staphylococcus saprophyticus and Klebsiella pneumoniae. E. coli contains a number of virulence factors including fimbriae, K capsule, and LPS endotoxin. The P fimbriae virulence factor of E. coli enables binding to uroepithelial cells, leading to cystitis and pyelonephritis. Treatment of UTI is most commonly with antibiotics such as trimethoprim-sulfamethoxazole.
Mehnert-Kay reviews the diagnosis and management of uncomplicated UTIs. She states most uncomplicated UTIs occur in women who are sexually active, with far fewer cases occurring in older women, those who are pregnant, and in men. E. coli is the leading cause of urinary tract infections, followed by S. saprophyticus. Trimethoprim-sulfamethoxazole has been the standard therapy for UTI; however, E. coli is becoming increasingly resistant to medications.
Simati et al. review dipstick urinalysis for the diagnosis of acute UTI. They state dipstick urinalysis moderately improves the accuracy of clinical symptoms in establishing or excluding the diagnosis of acute UTI in women. A positive nitrite test is more useful than a positive leukocyte esterase (LE) test, although both increase the odds of a UTI diagnosis. If nitrite and LE tests are negative, the odds of a UTI decrease by 40 to 60 percent.
Illustration A graphically demonstrates the virulence factors associated with E. coli. Illustration B is a micrograph showing the fimbriae of E. coli which contribute to the development of cystitis.
Answer 1: The LPS endotoxin of E. coli is the virulence factor which contributes to septic shock.
Answer 2: The K capsule of E. coli is the virulence factor which contributes to pneumonia and neonatal meningitis.
Answer 4: The majority of E. coli strains do not possess a flagella. Furthermore, flagella presence would not contribute to the pathogenesis of UTIs.
Answer 5: Exotoxin produced by E. coli contributes to its gastrointestinal pathogenicity (ex: EHEH, Shiga-like toxin) but does contribute to the pathogenesis of UTI's.
Mehnert-Kay SA. Diagnosis and management of uncomplicated urinary tract infections. Am Fam Physician. 2005 Aug 1;72(3):451-6. Review. PubMed PMID:
PMID:16100859 (Link to Abstract)
Simati B, Kriegsman B, Safranek S. FPIN's clinical inquiries. Dipstick urinalysis for the diagnosis of acute UTI. Am Fam Physician. 2013 May 15;87(10):Online. PubMed PMID:
PMID:23939456 (Link to Abstract)