For treating Methicillin-Sensitive Staphylococcus Aureus (MSSA), which of the following is an appropriate medication?

Nafcillin is the appropriate medication for treating Methicillin-Sensitive Staphylococcus Aureus (MSSA) infections. This antibiotic belongs to the penicillin class and is specifically designed to be effective against beta-lactamase-producing strains of Staphylococcus, such as MSSA. Its beta-lactam structure allows it to inhibit bacterial cell wall synthesis, leading to cell lysis and death.

Vancomycin is primarily used for Methicillin-Resistant Staphylococcus Aureus (MRSA) and does not target MSSA effectively. While it can treat some staphylococcal infections, it is reserved for resistant strains due to its route of administration and side effects.

Demeclocycline is a tetracycline antibiotic and is not typically used to treat staphylococcal infections, especially MSSA, owing to its broad spectrum and lack of specific activity against these organisms.

Liothyronine, a synthetic form of the thyroid hormone triiodothyronine, has no antibacterial properties and is unrelated to the treatment of bacterial infections.

Overall, nafcillin is the drug of choice for MSSA due to its targeted action and effectiveness in treating infections caused by this specific strain of Staphylococcus aureus