What antibiotics (Abx) are used to treat gastrointestinal (GI) infections?

From the Guidelines

For the treatment of community-acquired intra-abdominal infection of mild-to-moderate severity, the use of ticarcillin-clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline as single-agent therapy is recommended. The selection of an antimicrobial agent should be based on local microbiologic data, cost advantage, allergies, and formulary availability 1.

Key Considerations

• Coverage for obligate anaerobic bacilli should be provided for distal small bowel, appendiceal, and colon-derived infection and for more proximal gastrointestinal perforations in the presence of obstruction or paralytic ileus 1.
• Empiric coverage of Enterococcus is not necessary in patients with community-acquired intra-abdominal infection 1.
• The use of agents with substantial anti-Pseudomonal activity is not recommended for patients with mild-to-moderate community-acquired infection, as they may carry a greater risk of toxicity and facilitate the acquisition of more-resistant organisms 1.

Specific Recommendations

• For adult patients with mild-to-moderate community-acquired infection, combinations of metronidazole with cefazolin, cefuroxime, ceftriaxone, cefotaxime, levofloxacin, or ciprofloxacin are preferable to regimens with substantial anti-Pseudomonal activity 1.
• Azithromycin is recommended as the first-line agent for the treatment of dysentery and acute watery diarrhea with greater than mild fever, due to its efficacy against FQ-resistant Campylobacter and other bacterial causes 1.
• For confirmed Shigella, Campylobacter, or invasive Salmonella infections, ciprofloxacin 500mg twice daily for 3-5 days may be prescribed, but its use should be guided by local resistance patterns 1.

General Principles

• Antibiotics should be used judiciously, as they can disrupt gut flora and contribute to antibiotic resistance 1.
• Most GI infections improve with fluid replacement, rest, and dietary modifications, so antibiotics should be reserved for severe cases, immunocompromised patients, or specific bacterial pathogens confirmed by stool culture 1.

From the FDA Drug Label

Metronidazole tablets are indicated in the treatment of acute intestinal amebiasis (amebic dysentery) and amebic liver abscess. INTRA‑ABDOMINAL INFECTIONS, including peritonitis, intra‑abdominal abscess, and liver abscess, caused by Bacteroides species including the B. fragilis group To reduce the development of drug-resistant bacteria and maintain the effectiveness of metronidazole tablets and other antibacterial drugs, metronidazole tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria

Antibiotic treatment for GI infection:

• Metronidazole is indicated for the treatment of acute intestinal amebiasis and intra-abdominal infections, including those caused by Bacteroides species.
• The decision to use metronidazole should be based on the presence of susceptible bacteria and the severity of the infection.
• It is essential to use metronidazole only when necessary and to follow proper prescribing guidelines to minimize the development of drug-resistant bacteria 2.

Complicated Intra-Abdominal Infections (used in combination with metronidazole) caused by Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae, or Bacteroides fragilis Infectious Diarrhea caused by Escherichia coli (enterotoxigenic strains), Campylobacter jejuni, Shigella boydii†, Shigella dysenteriae, Shigella flexneri or Shigella sonnei† when antibacterial therapy is indicated.

Alternative antibiotic option:

• Ciprofloxacin can be used in combination with metronidazole for the treatment of complicated intra-abdominal infections.
• Ciprofloxacin is also indicated for the treatment of infectious diarrhea caused by certain bacterial strains, including Escherichia coli and Campylobacter jejuni 3.

From the Research

Antibiotics for GI Infection

• The use of antibiotics for GI infections is generally reserved for cases where a bacterial cause is suspected or confirmed 4.
• For acute gastroenteritis, antibiotics are only recommended for certain bacterial causes, such as Shigella, Vibrio cholerae, Campylobacter, and severe cases of Salmonella infection 4.
• Azithromycin is the preferred antibiotic for infections due to Shigella and Campylobacter, while ceftriaxone and ciprofloxacin are recommended for salmonellosis when antibiotic treatment is indicated 4.

Treatment of Enteric Fever

• The World Health Organization recommends treatment with azithromycin, ciprofloxacin, or ceftriaxone for enteric fever due to widespread resistance to older antimicrobials 5.
• Ceftriaxone may be an effective treatment for adults and children with enteric fever, with few adverse effects 5.
• Cefixime can also be used for treatment of enteric fever, but may not perform as well as fluoroquinolones 5.

Guideline for Antibiotic Use

• A guideline for antibiotic use in acute gastroenteritis recommends considering epidemiological factors, diagnostic tests, and indications for empirical antibiotics 6.
• The guideline aims to decrease antibiotic misuse and prevent antibiotic resistance 6.

Efficacy of Ciprofloxacin

• Ciprofloxacin has been shown to be effective in treating gastrointestinal infections, with excellent tolerability 7.
• Sequential intravenous/oral ciprofloxacin plus metronidazole has been compared to intravenous ceftriaxone plus metronidazole for treatment of complicated intra-abdominal infections, with similar clinical success rates 8.