From the Guidelines
Cipro (ciprofloxacin) has a higher incidence of Clostridioides difficile (C. difficile) colitis compared to Bactrim (trimethoprim/sulfamethoxazole). According to the most recent and highest quality study, fluoroquinolones like ciprofloxacin are among the highest-risk antibiotics for C. difficile infection, while trimethoprim/sulfamethoxazole carries a relatively lower risk 1. This difference occurs because fluoroquinolones cause more significant disruption to the normal gut microbiota, creating an environment where C. difficile can flourish. Ciprofloxacin has broader spectrum activity against anaerobic bacteria that normally help prevent C. difficile overgrowth.
When prescribing either medication, clinicians should consider this differential risk, especially in patients with additional risk factors for C. difficile infection such as advanced age, recent hospitalization, immunosuppression, or previous C. difficile infections. The study highlights that the daily increase in the risk of C. difficile acquisition during hospitalization suggests that duration of hospitalization may be a proxy for the duration and degree of exposure to the organism, likelihood of exposure to antibiotics, and severity of underlying illness 1.
Key points to consider:
- Fluoroquinolones, including ciprofloxacin, are high-risk antibiotics for C. difficile infection
- Trimethoprim/sulfamethoxazole carries a relatively lower risk
- Disruption of the intestinal microbiota by antibiotics is long-lasting, and risk of CDI increases both during therapy and in the 3-month period following cessation of therapy
- Clinicians should consider the differential risk when prescribing either medication, especially in patients with additional risk factors for C. difficile infection. Antibiotic stewardship practices recommend selecting narrower spectrum antibiotics when appropriate to reduce the risk of this potentially serious complication.
From the Research
Comparison of C. difficile Colitis Incidence
- The provided studies do not directly compare the incidence of C. difficile colitis between Bactrim (trimethoprim/sulfamethoxazole) and Cipro (ciprofloxacin) 2, 3, 4, 5, 6.
- However, it is known that the use of broad-spectrum antibiotics, such as fluoroquinolones (including ciprofloxacin), can disrupt the normal gut flora and increase the risk of C. difficile infection 5, 6.
- On the other hand, trimethoprim/sulfamethoxazole is also a broad-spectrum antibiotic, but its association with C. difficile infection is less clear 6.
- A study on the treatment of urinary tract infections notes that the prevalence of E. coli resistance to trimethoprim/sulphamethoxazole exceeds 20% in many North American regions, which may imply a higher risk of C. difficile infection with the use of this antibiotic 6.
- However, without direct comparative studies, it is difficult to determine which antibiotic has a higher incidence of C. difficile colitis.
Mechanism of Action and Resistance
- Ciprofloxacin, a fluoroquinolone, works by inhibiting bacterial DNA gyrase, and has a broad spectrum of activity against Gram-negative and some Gram-positive bacteria 5.
- Trimethoprim/sulfamethoxazole, on the other hand, works by inhibiting folic acid synthesis in bacteria 6.
- The development of resistance to ciprofloxacin is infrequent, except in certain settings such as pseudomonal respiratory tract infections in cystic fibrosis patients 5.
- The emergence of resistance to trimethoprim/sulphamethoxazole is a concern, particularly in the treatment of urinary tract infections 6.
Treatment of C. difficile Infection
- Fecal microbiota transplantation (FMT) has been shown to be effective in the treatment of recurrent C. difficile infection, with a high success rate and minimal adverse events 2, 3, 4.
- Antibiotics such as vancomycin and metronidazole are also used to treat C. difficile infection, but the risk of recurrence and resistance is a concern 2, 3.