Final answer:
The third and fourth generations of fluoroquinolones expanded the quinolone antibiotics' coverage to include more gram-positive bacteria, specifically S. pneumoniae, compared to earlier generations.
Step-by-step explanation:
The generation of quinolones that added activity against S. pneumoniae and more gram-positive cocci over previous generations of quinolones is the third and fourth generations of fluoroquinolones. These later generation of fluoroquinolones demonstrated improved efficacy against gram-positive bacteria, including the problematic S. pneumoniae.
Prior generations, such as the second generation, which included ciprofloxacin and ofloxacin, were more limited in their activity against gram-positive organisms but were effective against a broad spectrum of gram-negative bacteria. The advancements in the fluoroquinolones have provided clinicians with more options when treating infections, particularly when beta-lactam resistance is a concern. However, increasing resistance to fluoroquinolones is becoming an issue that limits therapeutic options for some infections.