NBEO Microbiology Practice Test

MRSA requires antibiotics that are active against resistant Staphylococcus aureus, especially when systemic treatment is needed. Vancomycin fits this need because it is a glycopeptide that inhibits cell wall synthesis by binding the D-Ala-D-Ala terminus, making it reliably effective against MRSA where many other antibiotics fail. This is why it’s the commonly used systemic option for ocular infections requiring MRSA coverage. The other drugs listed either don’t reliably cover MRSA or aren’t the standard systemic choice for ocular MRSA management (amoxicillin is a beta-lactam that MRSA resists; azithromycin and doxycycline have variable MRSA activity and aren’t the first-line systemic choice for ocular cases).