From the Guidelines
Amoxicillin is no longer recommended as a first-line treatment for E. coli infections due to high resistance rates, with approximately 75% of E. coli urinary isolates resistant to amoxicillin, as reported by the Global Antimicrobial Resistance Surveillance System (GLASS) in 2020 1.
Alternatives to Amoxicillin
Instead, alternative antibiotics such as nitrofurantoin, sulfamethoxazole-trimethoprim, or fosfomycin are recommended for the treatment of uncomplicated urinary tract infections (UTIs) caused by E. coli, as they have shown good in vitro activity against this pathogen 1.
- Nitrofurantoin is a commonly used antibiotic for UTIs, with an estimated clinical efficacy of 93% and microbiological efficacy of 88% 1.
- Sulfamethoxazole-trimethoprim is another option, with an estimated clinical efficacy of 93% and microbiological efficacy of 94% 1.
- Fosfomycin is a single-dose antibiotic that has shown clinical efficacy comparable to other first-line agents, although its bacterial efficacy is lower 1.
Considerations for Antibiotic Choice
When choosing an antibiotic, it is essential to consider local resistance patterns and the patient's individual risk factors for resistance, such as recent travel or previous antibiotic use 1.
- Local resistance rates should be taken into account, as they can vary significantly between regions and countries 1.
- Patient-specific factors, such as allergy history and medication interactions, should also be considered when selecting an antibiotic.
Importance of Culture and Sensitivity Testing
In cases of suspected resistance or complicated infections, culture and sensitivity testing should be performed to guide antibiotic therapy and ensure the most effective treatment is used 1.
- Culture and sensitivity testing can help identify the specific antibiotic resistance pattern of the E. coli isolate, allowing for targeted treatment.
- This approach can help reduce the risk of treatment failure and the development of further antibiotic resistance.
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 is effective against E. coli when the isolate is β-lactamase–negative. The drug label indicates that amoxicillin can be used to treat infections caused by susceptible E. coli in the genitourinary tract and skin and skin structure infections 2 2.
- Key points:
- Amoxicillin is indicated for the treatment of infections due to susceptible E. coli.
- The E. coli isolate must be β-lactamase–negative.
- Amoxicillin can be used to treat E. coli infections in the genitourinary tract and skin and skin structure.
From the Research
Amoxicillin versus E. coli
- The provided studies do not directly compare amoxicillin to E. coli resistance patterns 3, 4, 5, 6, 7.
- However, the studies discuss various antibiotics and their effectiveness against E. coli in urinary tract infections (UTIs).
- One study found that fluoroquinolones, such as ciprofloxacin and levofloxacin, had lower resistance rates in otherwise healthy women with uncomplicated UTIs compared to the hospital's antibiogram 3.
- Another study discussed the prevalence of fluoroquinolone resistance in E. coli causing community-acquired UTIs, but did not mention amoxicillin 4.
- A study from Korea found that fosfomycin, nitrofurantoin, and temocillin had excellent susceptibility profiles against E. coli, while ciprofloxacin and trimethoprim-sulfamethoxazole had higher resistance rates 5.
- A multicenter study identified risk factors for trimethoprim-sulfamethoxazole resistance in E. coli, including recurrent UTIs, genitourinary abnormalities, and recent use of trimethoprim-sulfamethoxazole 6.
- A review of traditional pharmacologic therapies for UTIs discussed various antibiotics, including trimethoprim-sulfamethoxazole, fluoroquinolones, and nitrofurantoin, but did not mention amoxicillin as a first-line treatment 7.
Resistance Patterns
- The studies suggest that E. coli resistance patterns vary depending on the antibiotic and the population being studied 3, 4, 5, 6.
- Fluoroquinolones, such as ciprofloxacin and levofloxacin, had lower resistance rates in some studies, while trimethoprim-sulfamethoxazole had higher resistance rates in others 3, 6.
- Fosfomycin, nitrofurantoin, and temocillin had excellent susceptibility profiles in one study 5.
Treatment Options
- The studies discuss various treatment options for UTIs, including fluoroquinolones, nitrofurantoin, fosfomycin, and trimethoprim-sulfamethoxazole 3, 4, 5, 6, 7.
- The choice of antibiotic should be guided by the patient's specific situation, including the presence of underlying medical conditions, recent antibiotic use, and local resistance patterns 6, 7.