Which monobactam can be used safely in patients with penicillin allergies and what is its spectrum?

Which monobactam can be used safely in patients with penicillin allergies and what is its spectrum?

• A. Imipenem; broad spectrum including Gram-positives
• B. Ceftriaxone; broad-spectrum including Gram-positives
• C. Aztreonam; active against Gram-negative aerobic bacteria; inactive against Gram-positive and anaerobes
• D. Meropenem; broad-spectrum, including anaerobes

Answer: (C)

Aztreonam is the monobactam that can be used safely in patients with penicillin allergies. It has activity mainly against Gram-negative aerobic bacteria (including many Enterobacterales and Pseudomonas), but it does not have activity against Gram-positive organisms or anaerobes. This narrow Gram-negative spectrum, combined with minimal cross-reactivity with penicillins, makes it a suitable option when Gram-negative coverage is needed and a penicillin allergy is a concern. The other listed agents have broader spectra that include Gram-positives and anaerobes, or come with greater concerns about cross-reactivity, so they’re not the best fit for this scenario.

Aztreonam is the monobactam that can be used safely in patients with penicillin allergies. It has activity mainly against Gram-negative aerobic bacteria (including many Enterobacterales and Pseudomonas), but it does not have activity against Gram-positive organisms or anaerobes. This narrow Gram-negative spectrum, combined with minimal cross-reactivity with penicillins, makes it a suitable option when Gram-negative coverage is needed and a penicillin allergy is a concern. The other listed agents have broader spectra that include Gram-positives and anaerobes, or come with greater concerns about cross-reactivity, so they’re not the best fit for this scenario.