What is the best empiric antibiotic regimen for bacterial colitis that is not Clostridioides difficile (C. diff)?

From the Guidelines

For bacterial colitis not caused by C. difficile, the recommended empiric antibiotic regimen is ertapenem or moxifloxacin as single-agent therapy, as they are active against enteric gram-negative aerobic and facultative bacilli and enteric gram-positive streptococci 1. The choice of antibiotic should be based on the severity of the infection, patient risk factors, and likelihood of specific pathogens.

• For adult patients with mild-to-moderate community-acquired infection, the use of ticarcillin-clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline as single-agent therapy or combinations of metronidazole with cefazolin, cefuroxime, ceftriaxone, cefotaxime, levofloxacin, or ciprofloxacin are preferable to regimens with substantial anti-Pseudomonal activity 1.
• 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.
• Routine aerobic and anaerobic cultures from lower-risk patients with community-acquired infection are considered optional in the individual patient but may be of value in detecting epidemiological changes in the resistance patterns of pathogens associated with community-acquired intra-abdominal infection and in guiding follow-up oral therapy 1.
• For higher-risk patients, cultures from the site of infection should be routinely obtained, particularly in patients with prior antibiotic exposure, who are more likely than other patients to harbor resistant pathogens 1.
• The specimen collected from the intra-abdominal focus of infection should be representative of the material associated with the clinical infection 1.
• Susceptibility testing for Pseudomonas, Proteus, Acinetobacter, Staphylococcus aureus, and predominant Enterobacteriaceae, as determined by moderate-to-heavy growth, should be performed, because these species are more likely than others to yield resistant organisms 1.
• Other options like ciprofloxacin plus metronidazole can also be considered as an alternative regimen 1. It is essential to note that the treatment should be tailored once the specific pathogen is identified, and supportive care with fluid replacement and electrolyte management is also crucial regardless of whether antibiotics are prescribed.
• Most cases of bacterial gastroenteritis are self-limiting and may not require antibiotics at all, with treatment decisions based on severity of symptoms, patient risk factors, and likelihood of specific pathogens 1.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Empiric Antibiotic Regimens for Bacterial Colitis

The best empiric antibiotic regimen for bacterial colitis that is not Clostridioides difficile (C. diff) depends on various factors, including the suspected pathogen and the patient's clinical presentation.

• For febrile dysenteric diarrhea, invasive bacterial enteropathogens such as Shigella, Salmonella, and Campylobacter should be suspected 2.
• Adults with febrile dysenteric diarrhea may be treated empirically with 1000mg azithromycin in a single dose 2.
• Other antibiotics such as ciprofloxacin, metronidazole, and rifaximin have been used in the management of infectious complications and fistulas in Crohn's disease 3.
• A combination of amoxicillin-clavulanate or metronidazole-with-fluoroquinolone may be used for outpatient diverticulitis, although amoxicillin-clavulanate may reduce the risk for fluoroquinolone-related harms 4.
• Antibiotic combination therapy with amoxicillin, tetracycline, and metronidazole has been shown to be effective in patients with active ulcerative colitis, including refractory or steroid-dependent cases 5.

Considerations for Antibiotic Choice

When choosing an empiric antibiotic regimen, it is essential to consider the potential risks and benefits of each antibiotic, as well as the patient's individual factors, such as prior antibiotic use and underlying medical conditions.

• The use of fluoroquinolones should be reserved for conditions with no alternative treatment options due to the risk of adverse effects 4.
• Antibiotic combination therapy may be effective in certain cases, but the risk of drug-related toxicities should be carefully monitored 5.
• The diagnosis of infectious colitis should be confirmed through standard stool culture and other diagnostic tests, and pathogen-specific antimicrobial therapy should be initiated once the laboratory diagnosis is made 2, 6.