From the Guidelines
For a Urinary Tract Infection (UTI) caused by gram-negative bacilli, the best antibiotic choice is typically a carbapenem, such as imipenem or meropenem, for severe infections, or alternatives like piperacillin-tazobactam, amoxicillin/clavulanic acid, or quinolones for less severe cases, as recommended by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) guidelines 1.
When considering the treatment of UTIs caused by gram-negative bacilli, it's crucial to differentiate between severe and non-severe infections.
- For patients with severe infections, including those with septic shock, carbapenems like imipenem or meropenem are strongly recommended as targeted therapy 1.
- For non-severe infections, particularly in the context of antibiotic stewardship, piperacillin-tazobactam, amoxicillin/clavulanic acid, or quinolones may be considered 1.
- Additionally, for complicated urinary tract infections (cUTI) without septic shock, aminoglycosides or IV fosfomycin may be conditionally recommended for short durations 1.
It's also important to consider the susceptibility pattern of the isolate and the potential for resistance when selecting an antibiotic.
- Step-down targeted therapy following carbapenems, using older beta-lactam/beta-lactamase inhibitors (BLBLI), quinolones, cotrimoxazole, or other antibiotics based on susceptibility, is considered good clinical practice 1.
- Tigecycline is not recommended for infections caused by third-generation cephalosporin-resistant Enterobacterales (3GCephRE) 1.
In the context of real-life clinical practice, the choice of antibiotic should be guided by local resistance patterns, the severity of the infection, and, when possible, urine culture results. Patients should be advised to complete the full course of antibiotics, stay hydrated, and seek medical attention if symptoms worsen or do not improve within 48 hours of starting treatment.
From the FDA Drug Label
Levofloxacin tablets are indicated for the treatment of complicated urinary tract infections due to Escherichia coli, Klebsiella pneumoniae, or Proteus mirabilis Levofloxacin tablets are indicated for the treatment of complicated urinary tract infections (mild to moderate) due to Enterococcus faecalis, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, or Pseudomonas aeruginosa Levofloxacin tablets are indicated for the treatment of uncomplicated urinary tract infections (mild to moderate) due to Escherichia coli, Klebsiella pneumoniae, or Staphylococcus saprophyticus
The best antibiotic for a Urinary Tract Infection (UTI) caused by gram-negative bacilli is levofloxacin (PO), as it is indicated for the treatment of UTIs due to Escherichia coli and Klebsiella pneumoniae, which are both gram-negative bacilli 2.
- Key points:
- Levofloxacin is effective against gram-negative bacilli such as Escherichia coli and Klebsiella pneumoniae
- Levofloxacin is indicated for the treatment of complicated and uncomplicated UTIs
- The FDA drug label supports the use of levofloxacin for the treatment of UTIs caused by gram-negative bacilli 2
From the Research
Treatment Options for UTI with Gram-Negative Bacilli
The treatment of urinary tract infections (UTIs) caused by gram-negative bacilli is a growing concern due to limited therapeutic options and increasing rates of antibiotic resistance 3, 4.
- First-Line Empiric Therapies: For acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females, recommended first-line empiric therapies include a 5-day course of nitrofurantoin or a 3-g single dose of fosfomycin tromethamine 3, 4.
- Second-Line Options: Second-line options include fluoroquinolones and β-lactams, such as amoxicillin-clavulanate 3, as well as oral cephalosporins like cephalexin or cefixime 4.
- Treatment for Specific Resistance Mechanisms:
- AmpC-β-lactamase-producing organisms: Fosfomycin, nitrofurantoin, fluoroquinolones, cefepime, piperacillin-tazobactam, and carbapenems are treatment options 3, 4.
- ESBL-producing Enterobacteriaceae: Nitrofurantoin, fosfomycin, fluoroquinolones, cefoxitin, piperacillin-tazobactam, carbapenems, ceftazidime-avibactam, ceftolozane-tazobactam, and aminoglycosides are potential treatments 3, 4.
- Carbapenem-resistant Enterobacteriaceae (CRE): Ceftazidime-avibactam, colistin, polymixin B, fosfomycin, aztreonam, aminoglycosides, and tigecycline are among the treatment options 3, 4.
- Multidrug-Resistant (MDR) Pseudomonas spp.: Treatment options include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, carbapenems, aminoglycosides, colistin, ceftazidime-avibactam, and ceftolozane-tazobactam 3, 4.
Considerations for Antibiotic Use
The use of fluoroquinolones for empiric treatment of UTIs should be restricted due to increased rates of resistance 3, 4. It is essential to use new antimicrobials wisely to avoid resistance development 4. Economic considerations and patient compliance are also crucial in the treatment of UTIs, with once-daily formulations like ciprofloxacin extended release offering convenient dosing and potentially decreasing treatment failures and the development of antimicrobial resistance 5, 6.
Clinical Trials and Efficacy
Clinical trials have demonstrated the efficacy of certain antibiotics in treating UTIs. For example, ceftolozane-tazobactam was found to be non-inferior to levofloxacin in the treatment of complicated urinary-tract infections, including pyelonephritis, and even indicated superiority 7. Ciprofloxacin once-daily and twice-daily regimens have been compared, with the twice-daily regimen showing slightly better eradication of bacteriuria but similar clinical cure rates 6.