Which antibiotic is most likely to have been previously prescribed for a patient with a MRSA abscess?

The antibiotic most likely to have been previously prescribed for a patient with a MRSA abscess is trimethoprim-sulfamethoxazole. This choice is significant because trimethoprim-sulfamethoxazole, often referred to as TMP-SMX, is known to be effective against methicillin-resistant Staphylococcus aureus (MRSA). It is commonly used in clinical practice for skin and soft tissue infections where MRSA is suspected or confirmed.

Trimethoprim-sulfamethoxazole combines two different antibiotics that work synergistically to inhibit bacterial folic acid synthesis, which is critical for bacterial growth and replication. Because of its effectiveness against MRSA and its relatively low cost, TMP-SMX is frequently selected for outpatient treatment of uncomplicated MRSA abscesses, especially when drainage is not sufficient as a sole treatment.

In contrast, other antibiotics mentioned may not be reliable choices for treating MRSA infections. For instance, cephalexin is a first-generation cephalosporin that primarily targets methicillin-sensitive Staphylococcus aureus (MSSA) and does not effectively combat MRSA. Doxycycline does have an indication for some MRSA infections, but TMP-SMX is more commonly used given the prevalence of