From the Guidelines
For uncomplicated urinary tract infections (UTIs), the recommended first-line empirical antibiotic therapy is nitrofurantoin 100 mg orally twice daily for 5 days, or trimethoprim-sulfamethoxazole (TMP-SMX) 160/800 mg (one double-strength tablet) orally twice daily for 3 days if local resistance rates are below 20%. This recommendation is based on the most recent and highest quality study available, which suggests that these antibiotics are effective and have a low propensity for collateral damage 1.
Key Considerations
- Fosfomycin 3 grams as a single oral dose is another effective option for uncomplicated UTIs 1.
- For patients with complicated UTIs or risk factors such as recent hospitalization, fluoroquinolones like ciprofloxacin 500 mg orally twice daily for 7 days may be considered, though resistance concerns have limited their use as first-line agents 1.
- In pregnant women, amoxicillin-clavulanate or cephalexin are safer options, but the choice of antibiotic should consider local resistance patterns, patient allergies, pregnancy status, and renal function 1.
- Empiric therapy should be adjusted based on urine culture results when available, and adequate hydration and urinary analgesics like phenazopyridine can help manage symptoms while antibiotics take effect.
Rationale
The choice of antibiotic for UTIs should target the most common uropathogens, particularly E. coli, which causes 75-95% of uncomplicated UTIs 1. The IDSA/European Society of Clinical Microbiology and Infectious Diseases (ESCMID) guideline recommends treatment durations depending on the type of antibiotic, including 5 days of nitrofurantoin, 3 days of TMP-SMX, or a single dose of fosfomycin 1. Fluoroquinolones are highly efficacious in 3-day regimens but have a high propensity for adverse effects and thus should not be prescribed empirically and should instead be reserved for patients with a history of resistant organisms 1.
Additional Options
- Pivmecillinam (400 mg bid for 3–7 days) is an appropriate choice for therapy in regions where it is available, because of minimal resistance and propensity for collateral damage, but it may have inferior efficacy compared with other available therapies 1.
- The fluoroquinolones, ofloxacin, ciprofloxacin, and levofloxacin, are highly efficacious in 3-day regimens but have a propensity for collateral damage and should be reserved for important uses other than acute cystitis and thus should be considered alternative antimicrobials for acute cystitis 1.
From the FDA Drug Label
To reduce the development of drug-resistant bacteria and maintain the effectiveness of sulfamethoxazole and trimethoprim tablets and other antibacterial drugs, sulfamethoxazole and trimethoprim tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to empiric selection of therapy Urinary Tract Infections For the treatment of urinary tract infections due to susceptible strains of the following organisms: Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis and Proteus vulgaris It is recommended that initial episodes of uncomplicated urinary tract infections be treated with a single effective antibacterial agent rather than the combination
The recommended empirical antibiotic therapy for a patient presenting with symptoms of a urinary tract infection (UTI) is trimethoprim-sulfamethoxazole or levofloxacin, as they are effective against susceptible strains of the following organisms:
- Escherichia coli
- Klebsiella species
- Enterobacter species
- Morganella morganii
- Proteus mirabilis
- Proteus vulgaris
- Staphylococcus saprophyticus It is essential to consider local epidemiology and susceptibility patterns when selecting empirical therapy, and to use a single effective antibacterial agent for initial episodes of uncomplicated UTIs 2 3.
From the Research
Empirical Antibiotic Therapy for UTI
The recommended empirical antibiotic therapy for a patient presenting with symptoms of a urinary tract infection (UTI) depends on various factors, including the patient's health status, local susceptibility patterns, and the presence of antibiotic-resistant bacteria.
- For acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females, the first-line empiric antibiotic therapy options are:
- High rates of resistance to trimethoprim-sulfamethoxazole and ciprofloxacin preclude their use as empiric treatment of UTIs in several communities, particularly if patients were recently exposed to them or are at risk of infections with extended-spectrum β-lactamases (ESBLs)-producing Enterobacteriales 4, 7
- Second-line options include oral cephalosporins such as cephalexin or cefixime, fluoroquinolones, and β-lactams, such as amoxicillin-clavulanate 4
Special Considerations
- For UTIs due to AmpC- β-lactamase-producing Enterobacteriales, treatment options include nitrofurantoin, fosfomycin, pivmecillinam, fluoroquinolones, cefepime, piperacillin-tazobactam, and carbapenems 4
- For UTIs due to ESBLs-E coli, treatment oral options include nitrofurantoin, fosfomycin, pivmecillinam, amoxicillin-clavulanate, finafloxacin, and sitafloxacin 4
- For UTIs caused by carbapenem-resistant Enterobacteriales (CRE), treatment options include ceftazidime-avibactam, meropenem/vaborbactam, imipenem/cilastatin-relebactam, colistin, fosfomycin, aztreonam, and cefiderocol 4
- For UTIs caused by multidrug-resistant (MDR)-Pseudomonas spp., treatment options include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, carbapenems, and ceftolozane-tazobactam 4