Which of the following is a characteristic of a broad-spectrum antibiotic?

A broad-spectrum antibiotic is characterized by its ability to target a wide range of both Gram-positive and Gram-negative bacteria. This makes it particularly useful in clinical settings where the specific bacterial pathogen causing an infection has not yet been identified, allowing for effective treatment of various bacterial infections without needing to wait for precise lab results.

This broader range of effectiveness is critical in managing infections that could be caused by multiple types of bacteria, which is especially common in initial treatments of bacterial infections where the exact organism is unknown. Such antibiotics are generally used when the risk of severe infection is high, and it's essential to initiate treatment quickly.

In contrast, the other options illustrate characteristics that do not align with broad-spectrum antibiotics. Specifically, addressing viral infections does not fall under the purview of antibiotics, limited effectiveness is a hallmark of narrow-spectrum antibiotics and fungal infections require antifungal medications instead of antibiotics. Each of these distinctions underscores why the chosen characteristic of broad-spectrum antibiotics focuses on their ability to act against a diverse collection of bacterial pathogens.