Is amoxicillin (amoxicillin) effective against Escherichia coli (E. coli)?

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Last updated: April 23, 2025 • View editorial policy

From the Guidelines

Amoxicillin is not recommended as a first-line treatment for E. coli infections due to high resistance rates, with a median of 75% of E. coli urinary isolates resistant to amoxicillin, as reported by the Global Antimicrobial Resistance Surveillance System (GLASS) in 2020 1.

Considerations for Treatment

When treating suspected E. coli infections, it's crucial to consider local antibiotic resistance patterns and, when possible, obtain culture and sensitivity testing to guide optimal antibiotic selection.

  • Local resistance patterns can significantly impact the effectiveness of amoxicillin and other antibiotics.
  • The use of amoxicillin-clavulanate (Augmentin) may be more effective against resistant E. coli strains due to the clavulanic acid component inhibiting beta-lactamases.
  • Other antibiotics like nitrofurantoin, trimethoprim-sulfamethoxazole, or fluoroquinolones may be more reliable choices for urinary tract infections caused by E. coli, depending on susceptibility testing.

Alternative Treatment Options

Alternative treatment options for E. coli infections include:

  • Nitrofurantoin, which has been shown to have good in vitro activity against E. coli in all countries investigated 2.
  • Trimethoprim-sulfamethoxazole, which is recommended for 3 days for uncomplicated cystitis and 14 days for pyelonephritis 3.
  • Fluoroquinolones, which are highly efficacious in 3-day regimens but have a high propensity for adverse effects and should be reserved for patients with a history of resistant organisms 3.

Importance of Resistance Patterns

The importance of considering local resistance patterns when selecting an antibiotic for E. coli infections cannot be overstated.

  • Resistance rates for amoxicillin are high, with a median of 75% of E. coli urinary isolates resistant to amoxicillin, as reported by GLASS in 2020 1.
  • The use of antibiotics with high resistance rates can lead to treatment failure and the development of further resistance.
  • Therefore, it is essential to consider local resistance patterns and obtain culture and sensitivity testing when possible to guide optimal antibiotic selection.

From the FDA Drug Label

Infections of the Genitourinary Tract: Amoxicillin for oral suspension is indicated in the treatment of infections due to susceptible (ONLY β-lactamase–negative) isolates of Escherichia coli, Proteus mirabilis, or Enterococcus faecalis Infections of the Skin and Skin Structure:Amoxicillin for oral suspension is indicated in the treatment of infections due to susceptible (ONLY β-lactamase–negative) isolates of Streptococcusspp. (α-and β-hemolytic isolates only), Staphylococcusspp., or E. coli.

Amoxicillin covers E. coli, but only if the isolates are β-lactamase–negative and susceptible 4.

From the Research

Amoxicillin Coverage for E. coli

  • The effectiveness of amoxicillin in covering E. coli is a concern due to increasing resistance rates.
  • According to 5, the resistance rate of E. coli to ampicillin is 66.9%, and to amoxicillin-clavulanic acid is 36.9%, indicating a significant level of resistance.
  • However, 6 suggests that amoxicillin-clavulanate can be a second-line option for treating UTIs, including those caused by E. coli.
  • It is essential to note that the resistance patterns of E. coli can vary by region and over time, as shown in 5 and 7.
  • The use of amoxicillin as a treatment option for E. coli infections should be guided by local susceptibility patterns and antibiotic usage policies.

Alternative Treatment Options

  • Other antibiotics, such as nitrofurantoin and fosfomycin, have been shown to be effective against E. coli, with low resistance rates, as reported in 8 and 9.
  • These alternatives may be considered as first-line treatment options for uncomplicated UTIs caused by E. coli.
  • The choice of antibiotic should be based on the specific circumstances of the patient and the local resistance patterns.

Resistance Patterns

  • The resistance patterns of E. coli to various antibiotics are a significant concern, with high resistance rates reported for some antibiotics, such as trimethoprim-sulfamethoxazole and ciprofloxacin, as shown in 5 and 7.
  • The use of antibiotics should be guided by susceptibility testing and local resistance patterns to minimize the development of resistance.
  • Regular monitoring of resistance patterns is crucial to ensure the effective treatment of E. coli infections, as emphasized in 5 and 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.