Which antibiotic is considered effective against Pseudomonas aeruginosa?

Pseudomonas aeruginosa is a gram-negative bacterium known for its resistance to many antibiotics and is often a concern in hospital-acquired infections and immunocompromised patients. Zosyn, which is a combination of piperacillin and tazobactam, is specifically designed to combat infections caused by Pseudomonas aeruginosa due to its broad-spectrum activity against gram-negative organisms. The piperacillin component has inherent activity against Pseudomonas, while tazobactam serves to inhibit β-lactamases, which can confer resistance, thereby enhancing the effectiveness of piperacillin.

The other antibiotics listed are generally not effective against Pseudomonas aeruginosa. Vancomycin primarily targets gram-positive bacteria and is not effective against most gram-negative organisms. Azithromycin and clarithromycin are macrolide antibiotics that are more suitable for treating respiratory infections caused by atypical bacteria and also are not reliable against Pseudomonas. Hence, Zosyn stands out as the appropriate choice for treating infections caused by this particular bacterium.