Urinary Tract Infections

Acute uncomplicated UTI:

• E coli (75-90%)

• Staphylococcus saprophyticus (5-15%)

  • Especially in young, sexually active women

• Klebsiella

• Proteus mirabilis

• Citrobacter

• Enterococcus

Complicated UTI:

• Same as above, but also:

• Pseudomonas

• Acinetobacter

• Morganella

• Staphylococcus

• Yeast

	Outpatients	Inpatients
Escherichia coli	75%	Common
Klebsiella	15%	Common
Proteus	5%	Common
Enterococci	2%	Common
Staphylococcus epidermidis	<2%	Common
Group B streptococci	<2%	Common
Pseudomonas	Rare	Common

• In 95% of cases, UTIs are monomicrobial

Diagnosis & Workup

• Urinalysis should be performed for all patients with possible UTI

  • >10 WBC/HPF indicates pyuria

  • Leukocyte esterase dipstick is generally sensitive, but can have false negs

  • WBC casts is strong evidence for pyelonephritis

  • Increased protein is common as well

• Urine culture allows for quantitation to differentiate contamination (usual) from active infection

  • Not required in sexually active women with early cystitis

  • More than 10⁵ organisms per mL indicates infection, but sympatomatic women can have as few as 10³ per mL

  • The IDSA recommends >10³ per mL as an indication of infection in symptomatic patients

  • Follow-up with repeat culture if symptoms relapse

• Ultrasound to image:

  • Patients with upper tract disease, and persistent fever, on antibiotics

  • Preschool girls with second UTI

  • Any male with UTI

• IV pyelogram to work up anatomic obstruction, but avoid in MM or AKI

• CT abdomen for perinephric abscess, anatomic defects, obstruction, calculi, etc

Principles of Management

Uncomplicated Cystitis

• Background:

  • Should be treated if symptomatic, and pregnant women should have all ASB treated as well

  • Most can be treated over the phone, without physical examiantion

  • TMP-SMX used to be the first line therapy in 1999, but now there is no single best agent

• Antibiotic Regimens

  • First-Line

    • TMP-SMX

      • Dose: 1 double strength tablet BID for 3 days

      • Increasing resistance, consider if local resistance <20%

    • Nitrofurantoin

      • Dose: 100 mg bid for 5-7 days

      • Resistance remains fairly low

      • Highly active against E coli and most non-E coli isolates

      • Proteus, Pseudomonas, Serratia, Enterobacter, and yeast are intrinsically resistant

      • Do NOT use to treat pyelonephritis, does not reach therapeutic levels in the tissue

    • Fosfomycin

      • Retains activity against a majority of uropathogens that produce extended spectrum beta-lactamases

      • Single 3 gram dose

      • This is less effective than a 5 day course of nitrofurantoin

    • Pivmecillinam

      • May not be available in Canada

  • Second-Line

    • Fluoroquinolones

      • Highly effective (cipro or levo), except for moxi (low urinary levels)

      • Issues:

        • Resistance

        • Side effects

          • Achilles tendinopathy

          • Irreversible neuropathy

      • Therefore, use when other choices are not reasonable

    • Beta-lactams

      • Less effective; fail to eliminate uropathogens from the vaginal reservoir

      • Many strains of E coli that are resistant to TMP-SMX are also resistant to amoxicillin and cephalexin

  • Duration of Therapy

    • Avoid short course (5 days) of therapy in men, upper tract symptoms, women with symptoms more than a week in duration, diabetics

Pyelonephritis

• Background:

  • Tissue-invasive disease

  • Treatment needs to work, and needs to reach therapeutic levels very quickly

  • There are high rates of TMP-SMX resistant E coli in patients with pyelonephritis

  • Requires a longer duration of therapy

  • Uncomplicated

  • responds to 7 days well, otherwise 14 days is reasonable

• Antibiotic Regimens

  • First-Line

    • Fluoroquinolones

      • PO or IV are bioequivalent

      • 7-day course is highly effective for initial management in the outpatient setting

      • Preferred for empiric therapy

    • TMP-SMX

      • PO x 14 days is effective for uncomplicated pyelonephritis if the pathogen is known to be susceptible

      • If the susceptibility is unknown, use with an initial dose of ceftriaxone 1 gram IV

    • Amox-clav

  • Parenteral (more serious disease)

    • Fluoroquinolones

    • Extended spectrum cephalosporin +/- aminoglycoside

      • IV ceftriaxone, if there is no history of MDR pathogen or recent hospitalizations

    • Carbapenem

    • Once there is clinical response, should switch to oral from parenteral

  • Higher-Risk Patients

    • Beta-lactam + beta-lactamase-inhibitor

      • Pip-tazo (pseudomonas)

    • Cefepime (pseudomonas coverage)

    • Carbapenem

      • ESBL

  • Consider previous urine cultures to guide initial empiric coverage

UTI in Pregnant Women

• Nitrofurantoin, ampicillin, and cephalosporins are relatively safe in early pregnancy

• Pregnant women with overt pyelonephritis should get parenteral beta-lactam +/- aminoglycoside

• AVOID:

  • Sulfonamides

  • Fluoroquinolones

Prevention of UTI

• Sexually active women:

  • Void after sex

  • Single-dose TMP-SMX after sex

• Anatomic defects and children:

  • Daily low dose (1/2 tab) TMP-SMX daily, or 50 mg nitrofurantoin daily

• Indwelling catheters:

  • Abx ppx is not effective, and selects for antibiotic-resistant pathogens

  • Remove catheters ASAP