What antibiotic should be used intravenously (IV) for an unknown gastrointestinal (GI) infection?

From the Guidelines

Treatment of Unknown Gastrointestinal Infection

For the treatment of an unknown gastrointestinal infection, intravenous (IV) antibiotic therapy with Piperacillin-Tazobactam (4.5 g every 6 hours) or Cefepime (2 g every 8 hours) plus Metronidazole (500 mg every 6 hours) is recommended 1. Alternatively, Meropenem (1 g every 8 hours) or Imipenem-Cilastatin (1 g every 8 hours) may be used, especially in patients at risk for infection with community-acquired ESBL-producing Enterobacteriaceae 1.

• The choice of antibiotic should be based on the severity of the infection, the patient's risk factors, and local antimicrobial resistance patterns.
• The duration of treatment typically ranges from 7 to 14 days, depending on the clinical response and identification of the causative pathogen.
• It is essential to note that the use of broad-spectrum antibiotics should be judicious and based on the clinical scenario to minimize the risk of resistance and side effects.
• In patients at high risk for infection with Enterococci, including immunocompromised patients or those with recent antibiotic exposure, Ampicillin (2 g every 6 hours) may be considered if not already being treated with Piperacillin-Tazobactam or Imipenem-Cilastatin 1.
• The dosages of antibiotics may vary based on renal function and other factors, and it is crucial to monitor serum drug concentrations and adjust the dosages accordingly 1.

From the FDA Drug Label

In patients with creatinine clearance less than or equal to 60 mL/min, the dose of cefepime for injection should be adjusted to compensate for the slower rate of renal elimination The recommended initial dose of cefepime for injection should be the same as in patients with normal renal function except in patients undergoing hemodialysis. Complicated Intra-abdominal Infections (used in combination with metronidazole) caused by E coli, viridans group streptococci, P. aeruginosa, K. pneumoniae, Enterobacter species, or B. fragilis.

For an unknown gastrointestinal infection, Cefepime can be used intravenously. The recommended dose is 2 g IV every 8 to 12 hours. However, the dose may need to be adjusted based on the patient's renal function.

• In patients with normal renal function, the recommended dose is 2 g IV every 8 to 12 hours.
• In patients with creatinine clearance less than or equal to 60 mL/min, the dose should be adjusted according to the recommended maintenance schedule in Table 11 2. It is also recommended to use Cefepime in combination with metronidazole for complicated intra-abdominal infections.

From the Research

Antibiotic Options for Unknown GI Infection

• The choice of antibiotic for an unknown gastrointestinal (GI) infection depends on various factors, including the severity of the infection, the patient's medical history, and the suspected causative pathogens.
• According to the studies, the following antibiotics have been used to treat complicated intra-abdominal infections:
  • Piperacillin/tazobactam 3, 4, 5
  • Imipenem/cilastatin 3, 6
  • Tigecycline 6
  • Moxifloxacin 4
  • Ciprofloxacin plus metronidazole 5
• These antibiotics have shown efficacy in treating various types of GI infections, including intra-abdominal infections, appendicitis, and abscesses.
• The choice of antibiotic should be guided by the patient's specific condition, the suspected causative pathogens, and the antibiotic's spectrum of activity.

Spectrum of Activity

• Piperacillin/tazobactam has a broad spectrum of activity against Gram-negative and Gram-positive bacteria, including Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa 3.
• Imipenem/cilastatin also has a broad spectrum of activity against Gram-negative and Gram-positive bacteria, including E. coli, K. pneumoniae, and P. aeruginosa 3, 6.
• Tigecycline has a broad spectrum of activity against Gram-negative and Gram-positive bacteria, including E. coli, K. pneumoniae, and Enterobacter species 6.
• Moxifloxacin has a broad spectrum of activity against Gram-negative and Gram-positive bacteria, including E. coli, K. pneumoniae, and P. aeruginosa 4.
• Ciprofloxacin plus metronidazole has a broad spectrum of activity against Gram-negative and Gram-positive bacteria, including E. coli, K. pneumoniae, and Bacteroides fragilis 5.

Clinical Efficacy

• The clinical efficacy of these antibiotics has been demonstrated in various studies, including randomized controlled trials 3, 6, 4, 5.
• Piperacillin/tazobactam and imipenem/cilastatin have been shown to be effective in treating intra-abdominal infections, with clinical success rates of 97% and 97%, respectively 3.
• Tigecycline has been shown to be effective in treating complicated intra-abdominal infections, with a clinical success rate of 86% 6.
• Moxifloxacin has been shown to be effective in treating complicated intra-abdominal infections, with a clinical success rate of 80% 4.
• Ciprofloxacin plus metronidazole has been shown to be effective in treating complicated intra-abdominal infections, with a clinical success rate of 74% 5.