True about methicillin-resistance Staphylococcus aureus (MRSA) is
**Core Concept**
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of Staphylococcus aureus that has developed resistance to beta-lactam antibiotics, including methicillin. This resistance is primarily due to the production of a modified penicillin-binding protein (PBP2a), which has a low affinity for beta-lactam antibiotics.
**Why the Correct Answer is Right**
MRSA produces the enzyme PBP2a, also known as PBP2', which has a molecular weight of approximately 78 kDa. This enzyme is encoded by the mecA gene, which is located on the staphylococcal cassette chromosome mec (SCCmec) element. The mecA gene is responsible for the production of PBP2a, which has a low affinity for beta-lactam antibiotics, such as methicillin, oxacillin, and nafcillin. This reduced affinity allows MRSA to evade the effects of these antibiotics and continue to grow and multiply.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the mechanism of resistance in MRSA. While it may mention the production of an enzyme, it does not identify PBP2a as the key enzyme responsible for resistance.
**Option B:** This option is incorrect because it refers to a different type of resistance mechanism, such as efflux pumps or altered target enzymes. While these mechanisms may be relevant to other types of antibiotic resistance, they are not the primary mechanism of resistance in MRSA.
**Option C:** This option is incorrect because it does not provide a clear explanation of the resistance mechanism in MRSA. It may mention the production of an enzyme, but it does not specify the type of enzyme or its role in resistance.
**Clinical Pearl / High-Yield Fact**
The production of PBP2a is a key factor in the development of MRSA resistance, and it is essential to understand this mechanism to develop effective treatment strategies. Additionally, the mecA gene is a target for molecular diagnostic tests to detect MRSA.
**Correct Answer: C.**