Which characteristics define MRSA?

The defining characteristic of MRSA, or Methicillin-Resistant Staphylococcus aureus, is its resistance to methicillin and other beta-lactam antibiotics. This resistance arises due to genetic mutations that enable the bacteria to survive despite the presence of these antibiotics. MRSA infections can be more challenging to treat compared to non-resistant strains of Staphylococcus aureus, as they require alternative, often more potent antibiotics.

In contrast, the other options do not accurately describe MRSA. A non-resistant strain of Staphylococcus aureus would not exhibit the resistance characteristic that defines MRSA. Labeling MRSA as a type of Gram-negative bacilli is also incorrect, as Staphylococcus aureus is a Gram-positive cocci. Lastly, a harmless bacteria found in the gut does not apply here; MRSA typically resides on the skin or in the nasal passages and can lead to serious infections when it enters the body. Therefore, the correct characterization of MRSA pertains to its resistance to methicillin, highlighting its clinical significance and the need for careful antibiotic management.