From the Guidelines
Bactrim (trimethoprim-sulfamethoxazole) is effective against E. coli, but its use should be guided by local resistance rates and susceptibility testing, as recommended by the American College of Physicians in 2021 1.
Key Points to Consider
- The American College of Physicians recommends short-course antibiotics with either nitrofurantoin for 5 days, trimethoprim–sulfamethoxazole (TMP–SMZ) for 3 days, or fosfomycin as a single dose for women with uncomplicated bacterial cystitis 1.
- TMP–SMZ is an appropriate choice for therapy if local resistance rates of uropathogens causing acute uncomplicated cystitis do not exceed 20% or if the infecting strain is known to be susceptible, as stated in the 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases 1.
- Typical adult dosing for uncomplicated urinary tract infections caused by E. coli is one double-strength tablet (160mg trimethoprim/800mg sulfamethoxazole) every 12 hours for 3-5 days.
- Patients should be aware of potential side effects, including rash, nausea, and sun sensitivity, and those with sulfa allergies, certain blood disorders, or kidney disease should not take Bactrim.
Important Considerations
- Resistance to Bactrim has been increasing in some regions, so susceptibility testing may be necessary in complicated infections.
- The threshold of 20% as the resistance prevalence at which the agent is no longer recommended for empirical treatment of acute cystitis is based on expert opinion derived from clinical, in vitro, and mathematical modeling studies 1.
- Bactrim may interact with certain medications like warfarin and methotrexate, and patients should take the full course of antibiotics even if symptoms improve and drink plenty of water during treatment.
From the FDA Drug Label
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 Traveler’s Diarrhea in Adults: For the treatment of traveler’s diarrhea due to susceptible strains of enterotoxigenic E. coli. Aerobic gram-negative bacteria Escherichia coli (including susceptible enterotoxigenic strains implicated in traveler’s diarrhea)
Bactrim is effective against E. coli. The drug label indicates that Bactrim can be used to treat urinary tract infections and traveler's diarrhea caused by susceptible strains of E. coli 2, 2.
- Key points:
From the Research
Effectiveness of Bactrim against E. coli
- Bactrim, also known as trimethoprim/sulfamethoxazole (TMP/SMX), is an antibiotic commonly used to treat urinary tract infections (UTIs) caused by E. coli.
- According to a study published in 2019 3, TMP/SMX was found to be less effective against E. coli, with a lower sensitivity rate compared to other antibiotics such as fosfomycin, pivmecillinam, and nitrofurantoin.
- Another study published in 2014 4 found that TMP/SMX had a resistance rate of 29.2% against E. coli, which is relatively high compared to other antibiotics.
- A more recent study published in 2024 5 found that E. coli resistance rates to TMP/SMX were around 18%, which is still relatively high.
- Other studies have also reported high resistance rates of E. coli to TMP/SMX, ranging from 33% to 42% 6, 7.
- Overall, the evidence suggests that Bactrim may not be the most effective antibiotic against E. coli due to high resistance rates.
Alternative Treatment Options
- Fosfomycin, pivmecillinam, and nitrofurantoin have been shown to be more effective against E. coli, with lower resistance rates 3, 4, 5.
- These antibiotics may be considered as alternative treatment options for UTIs caused by E. coli.
- However, it is essential to note that antibiotic resistance patterns can vary depending on the region and population, and local resistance data should be consulted to guide treatment decisions.