Diagnosis of MRSA is based primarily on:

• A. History and characteristic appearance of the lesion
• B. Imaging studies
• C. Bacterial culture results only
• D. Blood tests

Answer: (A)

Diagnosing MRSA hinges on identifying the organism and its resistance, not just how the infection looks or the patient’s history. A skin or soft tissue infection can be caused by many pathogens, so you can’t confirm MRSA from appearance alone. The gold standard is obtaining a specimen from the infection and showing Staphylococcus aureus with methicillin resistance through culture and susceptibility testing (or a molecular test for the mecA gene). Imaging may show how extensive the infection is, but it doesn’t tell you the organism or its resistance. Blood tests can indicate that an infection is present, but they don’t identify MRSA. So, culture results demonstrating MRSA are the most reliable basis for diagnosis and guiding treatment.