Which of the following combinations is used for GI tract infections?

The combination of cefazolin plus metronidazole is commonly used for gastrointestinal (GI) tract infections due to their complementary mechanisms of action. Cefazolin is a first-generation cephalosporin antibiotic that is effective against a variety of gram-positive and some gram-negative bacteria. Its effectiveness makes it a good choice for empirical treatment of infections that may involve some of the common bacteria found in the GI tract.

Metronidazole, on the other hand, is particularly effective against anaerobic bacteria, including those commonly found in the gut such as Bacteroides and Clostridium species. The combination of these two agents provides broad coverage, addressing both aerobic and anaerobic organisms that can cause GI infections. This broad-spectrum coverage is often necessary when treating infections that might involve polymicrobial flora.

While other combinations may have their own benefits, they either lack adequate coverage for the anaerobic organisms predominant in GI infections or are not typically indicated for this type of infection. For example, doxycycline plus clindamycin may not be as effective as a first-line treatment, and ciprofloxacin plus aztreonam may not provide the necessary coverage of anaerobic bacteria. Vancomycin plus piperacillin, while effective in some cases