Effectiveness of Aztreonam for E. coli Infections
Aztreonam is highly effective for treating E. coli infections, as it is specifically indicated for various infections caused by Escherichia coli including urinary tract infections, lower respiratory tract infections, septicemia, skin and skin-structure infections, and intra-abdominal infections. 1
Mechanism of Action and Spectrum of Activity
- Aztreonam is a monobactam antibiotic that acts by inhibiting bacterial cell wall synthesis, with specific activity against gram-negative aerobic bacteria including E. coli 1
- It maintains effectiveness in the presence of some beta-lactamases produced by gram-negative bacteria, making it valuable for treating certain resistant strains 1
- Aztreonam has minimal activity against gram-positive bacteria and anaerobes, resulting in minimal disruption to the normal anaerobic gut flora 2, 3
FDA-Approved Indications for E. coli Infections
- Urinary tract infections (both complicated and uncomplicated), including pyelonephritis and cystitis 1
- Lower respiratory tract infections, including pneumonia and bronchitis 1
- Septicemia caused by E. coli 1
- Skin and skin-structure infections, including postoperative wounds, ulcers, and burns 1
- Intra-abdominal infections, including peritonitis 1
- Gynecologic infections, including endometritis and pelvic cellulitis 1
Clinical Efficacy Against E. coli
- Aztreonam demonstrates excellent in vitro activity against E. coli with MIC90 values typically ≤1.6 mg/L 3
- Clinical studies have shown high efficacy rates in treating E. coli infections, with rapid morphological changes observed in E. coli cells within minutes after administration 4
- In urinary tract infections specifically, aztreonam achieves high urinary concentrations (>480 μg/mL within 5 minutes of administration), far exceeding the MIC for E. coli 4
Special Considerations for Use
- For systemic infections, aztreonam must be administered parenterally (IV or IM) as oral bioavailability is very low (approximately 1%) 3
- Dosing regimen typically involves administration every 6-8 hours for moderate to severe infections, with 12-hour intervals sufficient for less severe infections 3
- For mixed infections where gram-positive or anaerobic organisms may be present, combination therapy is recommended 1, 2
- No dosage adjustment is needed for patients with hepatic dysfunction, but dose adjustments are required for patients with renal impairment 1, 2
Potential Role in Resistant Infections
- Aztreonam has demonstrated efficacy against E. coli strains resistant to other antibiotics including ampicillin, carbenicillin, cefazolin, cefamandole, cefoxitin, and gentamicin 5
- For metallo-β-lactamase-producing carbapenem-resistant Enterobacterales, aztreonam combined with ceftazidime-avibactam is recommended as it is not hydrolyzed by metallo-β-lactamases 6
- This combination has shown significantly lower 30-day mortality (19.2% vs 44%) compared to other treatment options for these highly resistant infections 6
Safety Profile
- Aztreonam has a favorable safety profile with low incidence of serious adverse effects 5
- It demonstrates minimal cross-reactivity with other beta-lactams, making it potentially suitable for patients with penicillin allergies 2, 7
- As a weak hapten with slight allergenicity, it has lower immunogenic potential compared to many other beta-lactam antibiotics 7
Aztreonam represents an effective and well-tolerated option for treating E. coli infections across multiple body sites, with particular value in settings where aminoglycoside toxicity is a concern or where resistance to other antibiotics is present.