Colitis is inflammation of the large intestine. This inflammation can lead to various uncomfortable symptoms, including abdominal pain, diarrhea, fatigue, and weight loss. While many factors can contribute to colitis, antibiotics play a significant role in treating specific forms of the condition, particularly those caused by bacterial infections.
Types of Colitis Where Antibiotics Are Used
Antibiotics are specifically indicated for colitis stemming from bacterial infections. This includes infectious colitis caused by pathogens such as Salmonella, Shigella, and Campylobacter, often acquired through contaminated food or water. In these cases, antibiotics can shorten the illness duration and reduce the shedding of the bacteria, which limits disease transmission.
A distinct type of colitis where antibiotics are used is Clostridioides difficile (C. diff) colitis, also known as pseudomembranous colitis. C. diff is a bacterium that can naturally reside in the intestines, but certain antibiotic treatments can disrupt the normal balance of gut bacteria, allowing C. diff to overgrow and produce toxins that cause inflammation. This condition is a common complication of antibiotic use itself.
Antibiotics are generally not the primary treatment for inflammatory bowel diseases (IBD) like Ulcerative Colitis or Crohn’s Disease, which are believed to involve an overactive immune system. However, antibiotics may be prescribed for specific complications that arise in IBD patients, such as abscesses or fistulas. They can also be used to manage bacterial overgrowth or to reduce intestinal inflammation. For example, antibiotics like metronidazole or ciprofloxacin are often used for perianal fistulas and abscesses in Crohn’s disease.
Common Antibiotics and Their Mechanisms
For Clostridioides difficile infection (CDI), fidaxomicin is a recommended antibiotic, typically given as 200 mg twice daily for 10 days, as it may have a lower risk of recurrence compared to vancomycin. Vancomycin, another common antibiotic for C. diff, is often prescribed at a dose of 125 mg orally four times daily for 10-14 days. It works by inhibiting bacterial cell wall synthesis, specifically by binding to D-Ala-D-Ala termini of lipid II, which prevents peptidoglycan assembly.
Metronidazole, while once a first-line agent for C. diff, is now often reserved for mild-to-moderate cases or when other options are unavailable, typically at 500 mg three times daily for 10-14 days. Its exact mechanism of resistance in C. difficile is not fully understood, but it is thought to involve alterations in bacterial enzymes and metabolic pathways. This antibiotic is effective against anaerobic bacteria and certain parasites.
For other bacterial causes of infectious colitis, such as Salmonella and Shigella, ciprofloxacin or azithromycin may be used. Ciprofloxacin, a fluoroquinolone antibiotic, inhibits bacterial DNA synthesis by targeting DNA gyrase and topoisomerase IV, enzymes necessary for bacterial DNA replication and cell division. Azithromycin, a macrolide antibiotic, works by inhibiting bacterial protein synthesis, which prevents bacteria from growing and reproducing. Azithromycin has also demonstrated anti-inflammatory effects in some studies, which may contribute to its benefits in colitis.
What to Expect During Treatment
Patients undergoing antibiotic treatment for colitis may experience common side effects such as nausea, vomiting, abdominal pain, cramping, and diarrhea. These gastrointestinal issues can arise because antibiotics, while targeting harmful bacteria, can also disrupt the balance of beneficial bacteria in the gut. Taking antibiotics with food can sometimes help to reduce stomach upset.
Completing the full course of antibiotics is important, even if symptoms improve before the medication is finished. Stopping treatment early can leave behind surviving bacteria, which may then multiply and cause the infection to return, often in a more resistant form, contributing to the broader issue of antibiotic resistance.
A concern with antibiotic use is the potential for recurring Clostridioides difficile infection. Antibiotics can disturb the healthy gut flora, creating an environment where C. diff can flourish. Recurrence of C. diff is common, with rates around 20% after an initial episode and increasing to 45-60% after a first recurrence.
Probiotics, such as Lactobacillus rhamnosus GG or Saccharomyces boulardii, may be recommended by healthcare providers to help restore the gut microbiome and reduce the risk of antibiotic-associated diarrhea and C. diff colitis. While some research suggests probiotics can help, it is important to discuss their use with a healthcare provider, as some studies indicate they might delay the natural recovery of the gut microbiome. Follow up with a healthcare provider to monitor recovery and address any persistent symptoms.