Adult Urinary Tract Infections

CHAPTER 25 Adult Urinary Tract Infections

David M. Albala, MD and
Udaya Kumar, MD, FRCS Urol, Dip Urol (Lon)

How common are urinary tract infections (UTIs) in young women?

UTIs occur in approximately 1% of schoolgirls (age 5–14). This proportion rises to 4% by young adulthood.

Should patients with asymptomatic bacteriuria be treated?

Pregnant women, children younger than 4 years, patients with severe diabetes, and patients with Proteus infections should be treated regardless of symptoms.

Which bacteria are urea splitting?

Majority are Proteus and Providencia species. Pseudomonas, Klebsiella, Staph. epidermidis, and mycoplasma are also capable of producing urease. Escherichia coli is not a urea-splitting organism.

What is emphysematous pyelonephritis?

It is a rare complication of pyelonephritis that can occur in diabetic patients. Nonresolving pyelonephritis despite therapy and the triad of fever, vomiting, and flank pain should be investigated. Presence of intraparenchymal gas on plain kidney, ureter, bladder (KUB) or computed tomography (CT) is diagnostic.

What is significant bacteriuria?

The number of bacteria that exceeds the number usually caused by contamination. 10² CFU/mL or more of a known pathogen in a patient with dysuria would be significant. Previously ≥10⁵ had been the cutoff limit. However, 20% to 40% of women with symptomatic UTIs had colony counts between 10⁴ and 10⁵.

What are bacterial pili?

Bacteria have surface structures called adhesins to mucosal surfaces. The most important adhesins are long filamentous appendages called pili fimbriae.

What is phase variation?

Changes in environmental growth conditions of bacteria can cause them to rapidly shift between piliated and nonpiliated phases.

What patient genetic factors affect susceptibility to UTIs?

Variation in bacterial adherence to vaginal, urethral, and buccal cell surfaces is genetically determined. Women with nonsecretor blood group phenotypes are more prone to UTIs.

How common are E. coli infections?

In the community setting, E. coli account for 85% of the UTIs. In the hospital setting, this proportion reduces to 50%.

What tests are used to localize UTIs to the upper or lower tract?

Fairley bladder washout and Stamey ureteral catheterization tests.

How accurate are clinical signs in localizing UTIs to the upper or lower tract?

Less than 50%. Fever and loin pain with significant bacteriuria, traditionally taught to be diagnostic of pyelonephritis, may occur with cystitis alone. Conversely, in patients with only bladder symptoms, the upper urinary tract is often involved.

What is the recommended duration of therapy for uncomplicated UTIs?

In a patient with a structurally normal urinary tract, a single dose or a 3-day course of antimicrobial treatment is adequate. Success rates are lower with single-dose therapy compared to multiday regimens. In men, all UTIs should be presumed complicated and treated for 7 days or more and an underlying cause sought.

Is antibiotic prophylaxis necessary for TURP?

No. If the preop urine shows no growth (<10² CFU/mL), prophylaxis is not necessary. In patients with significant growth, urethral catheters, risk of endocarditis, or whose bacterial status is unknown, prophylaxis is warranted. The risk of bacteremia is 50% if antimicrobials are not given when a UTI is present.

What antibiotics are suitable as prophylaxis for transrectal biopsy of the prostate?

Metronidazole with ampicillin or trimethoprim-sulfamethoxazole (TMP–SMX) is often used. A fluoroquinolone is a suitable alternative. Due to increasing resistance patterns, a rectal culture prior to the biopsy is now recommended by some experts.

When are imaging studies needed in UTIs?

Infections in males, febrile infections, failure to respond to appropriate therapy, bacterial persistence, and suspected urinary obstruction warrant imaging studies.

What are the common causes of unresolved bacteriuria during therapy?

• Bacterial resistance to drug (resistance may develop during the course of therapy).

• Mixed bacterial growth with varying drug susceptibilities.

• Rapid reinfection with a new organism.

• Renal insufficiency.

• Papillary necrosis.

• Bladder or Staghorn calculi.

• Self-inflicted infections or deception in taking medications.

• Urinary obstruction.

• Enterovesical fistulas.

What is bacterial persistence?

Despite clearance of bacteriuria with appropriate antimicrobial treatment, the same organism can reappear in the urinary tract from a site within the urinary tract that was excluded from the high concentrations of the antimicrobial agent, for example, a struvite stone.

Which antibiotics are suitable for long-term, low-dose prophylaxis?