Acute uncomplicated urinary tract infection (UTI) is one of the most common bacterial infections in adults that may involve the lower or upper urinary tract or both.
Acute cystitis is an infection limited to the lower urinary tract while acute pyelonephritis is an infection that involves the upper urinary tract (renal parenchyma and pelvicaliceal system) that usually has significant bacteriuria.
Recurrent UTI is characterized by 2 episodes of uncomplicated UTI in the last 6 months or ≥3 episodes with positive cultures in the last 12 months in patients with no structural or functional abnormalities.

Principles of Therapy

  • Choice of antibiotic for empirical therapy should be based on spectrum and susceptibility patterns of uropathogens, efficacy, tolerability, adverse effects including ecological effects, availability, and cost
  • No specific antibiotic regimen is recommended for pregnant women since all antibiotics studied were shown to be effective
  • In postmenopausal women, treatment of acute cystitis and pyelonephritis is the same to that in premenopausal women; however, short-term treatment in cystitis is not well-established

Acute Uncomplicated Pyelonephritis

  • Selection of antimicrobial agent will depend on local sensitivity patterns of uropathogens, whether or not the patient is hospitalized, and the relative costs of therapy
    • In cases where local resistance patterns are not known, empirical therapy should include initial intravenous (IV) dose of a long-acting parenteral antimicrobial agent and starting with a broader-spectrum agent and then narrowing the therapy when laboratory results are available
    • Patients with signs of urosepsis should be given empiric antimicrobial therapy with coverage for ESBL-producing organisms  
    • Oral therapy should always be considered in patients with mild to moderate symptoms
    • Parenteral therapy should be used in patients who are too ill to take oral antibiotic
  • Patient should be treated for a total of 7-14 days
    • Therapy for >14 days has not shown any benefit and is not recommended except in relapse cases caused by the same pathogen


Acute Uncomplicated Cystitis

First-line Options
  • Appropriate agents because of minimal resistance and tendency for ecological adverse effects (eg minimal effect on normal fecal flora)
    • Fosfomycin and Nitrofurantoin should not be used if early pyelonephritis is suspected
  • Fosfomycin (single dose)
    • A phosphonic acid derivative that has activity against both Gram-negative and Gram-positive bacteria
    • Has inferior microbiological efficacy rate but with comparable clinical efficacy rate as compared with standard short-course regimens
    • In vitro studies have shown activity against Vancomycin-resistant enterococci (VRE), Methicillin-resistant S aureus (MRSA), and extended spectrum β-lactamase (ESBL)-producing Gram-negative rods
  • Nitrofurantoin (for 5-7 days)
    • Antibacterial activity is limited to the urinary tract and is suitable only for the treatment or prophylaxis of uncomplicated urinary tract infections (UTI)
    • Has low resistance rates and with 88-93% clinical cure rate and 81-92% bacterial cure rate based on studies
      • With similar clinical and microbiological cure rates as with Co-trimoxazole
Alternative Agents
  • Cephalosporins and aminopenicillins with or without β-lactamase inhibitors
    • Recommended only in patients with uncomplicated cystitis when other recommended agents cannot be used
    • Have inferior efficacy in managing acute cystitis which is probably due to persistence of the vaginal reservoir for infection; these antimicrobials also cause ecological collateral damage
    • Broad-spectrum cephalosporins have been shown to be associated with ESBL resistance among Gram-negative bacteria
    • Amoxicillin or Ampicillin alone is not recommended to be used for empirical treatment
  • Fluoroquinolones (for 3 days)
    • Remain very effective for the treatment of acute cystitis however has increased resistance rate
    • Recommended to be used only in cases where other agents cannot be used due to the possibility of promoting resistance among uropathogens and other organisms that can cause more serious infections at other sites
      • Increased usage was shown to increase rates of MRSA
    • Overall clinical and microbiological efficacy rates are consistently high
    • Single-dose therapy is available but with possibly lower efficacy rates than with longer regimens
  • Co-trimoxazole (for 3 days)
    • Remains to be effective in treating patients with acute uncomplicated cystitis and may be considered in areas where resistance rate to E coli is <20%
      • Has early clinical and microbiological cure rates of 90-100%
    • Use is associated with increased resistance but generally does not have a tendency for ecological adverse effects
    • Not to be given in the last trimester of pregnancy
  • Trimethoprim (for 5 days)
    • May be considered in areas where resistance rate to E coli is <20%
    • Not to be given in the first trimester of pregnancy
  • Pivmecillinam (for 3-7 days) 
    • An extended Gram-negative spectrum penicillin that is used only for the treatment of UTI 
    • Has a low risk of selection for resistance and because of its low resistance rates, it is an agent of choice in some European countries 
    • Randomized trials showed clinical efficacy is less than the other recommended agents

Acute Uncomplicated Pyelonephritis

Fluoroquinolones (for 7-10 days)
  • Recommended as 1st-line oral therapeutic option in areas with <10% resistance rate to E coli, parenteral in severe cases
  • 3rd generation oral cephalosporins may be used as an alternative agent in patients with mild-moderate pyelonephritis
    • Studies have demonstrated similar clinical efficacy as with Ciprofloxacin
    • An initial parenteral dose of Ceftriaxone is recommended when Cefpodoxime, Ceftibuten or Co-trimoxazole was used empirically
  • Parenteral cephalosporins may be given in hospitalized patients in areas with ESBL-producing E coli resistance rates of <10%
    • An initial parenteral dose of Ceftriaxone is recommended in areas with >10% fluoroquinolone-resistance rate or when Co-trimoxazole or oral β-lactam agents were used empirically
      • Shown to significantly improve the microbiological eradication rate and moderately improve the clinical cure rates in patients with resistance to Co-trimoxazole
      • Combination of Ceftriaxone and Co-trimoxazole was shown to result in improved clinical and bacterial cure rates
  • Ceftolozane/tazobactam and Ceftazidime/avibactam can also be used as empirical parenteral therapies in uncomplicated pyelonephritis 

Aminopenicillin with β-lactamase inhibitor

  • Cannot be given as empirical therapy for acute pyelonephritis but can be used after susceptibility testing has shown growth of susceptible Gram-positive organism
  • May be given in hospitalized patients in infections with known susceptible Gram-positive pathogens
  • May be considered in areas with fluoroquinolone-resistant and ESBL-producing E coli (>10%)
    • An initial parenteral 24-hour dose of aminoglycoside is recommended in areas with >10% fluoroquinolone resistance rate or when oral β-lactam agents were used empirically
  • May be considered in areas with >10% rates of fluoroquinolone-resistant and ESBL-producing E coli
Co-trimoxazole (for 14 days)
  • Cannot be given as empirical therapy due to increasing E coli resistance rates but can be used after sensitivity has been confirmed through susceptibility testing

Recurrent UTI

  • Should be given after eradication of UTI has been confirmed through a negative culture obtained 1-2 weeks after treatment
  • Co-trimoxazole, Nitrofurantoin, Cefalexin, Cefaclor, Trimethoprim, or a quinolone (Norfloxacin or Ciprofloxacin) may be given as continuous daily antibiotic prophylaxis for 3-12 months
  • Single-dose post-coital prophylaxis (eg Co-trimoxazole, Nitrofurantoin, Cefalexin, Norfloxacin, Ciprofloxacin, Ofloxacin) should be given to women with recurrent UTI associated with sexual intercourse
  • Continuous or post-coital prophylaxis with Nitrofurantoin or Cefalexin may be given to pregnant patients at risk of recurrent UTI when non-antimicrobial interventions have been unsuccessful
    • Not advised during the last 4 month of pregnancy
  • Acute self-treatment with Co-trimoxazole, Norfloxacin or Ciprofloxacin may be an option in women with clearly documented recurrent infections and compliant with medical instructions who are not suitable for or unwilling to take the long-term daily prophylaxis
    • Patient identifies infection based on her symptoms, performs her own culture, and starts a standard course of empiric treatment
  • Co-trimoxazole and Norfloxacin as prophylactic agents were shown to reduce the recovery rate of aerobic Gram-negative uropathogens
  • Nitrofurantoin intermittently sterilizes the urine and possibly inhibits bacterial attachment causing lower recurrence rate
  • Immunoactive prophylaxis can be recommended for women with recurrent UTI 
  • Vaginal Estrogen may be advised to postmenopausal women who experience recurrent UTI
    • Has been shown to cause reappearance of vaginal lactobacilli which lowers vaginal pH preventing the overgrowth and colonization of enterobacteriaceae in the vagina
  • Cranberry products and probiotic lactobacilli may be helpful
  • Acupuncture may be an alternative option in preventing recurrent UTI in women who are unresponsive to or intolerant of antibiotic prophylaxis
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