Which two organisms is Mupirocin effective against?

• A. Strep and Klebsiella
• B. Staph and Strep
• C. E. coli and Pseudomonas
• D. MRSA and MSSA

Answer: (B)

Mupirocin is a topical antibiotic that is primarily effective against certain types of Gram-positive bacteria, particularly Staphylococcus aureus (including methicillin-sensitive strains, MSSA) and Streptococcus species (Strep). Its mechanism of action involves inhibiting bacterial protein synthesis, which is essential for the growth and reproduction of these microorganisms.

The effectiveness of mupirocin against Staphylococcus aureus is particularly significant in the context of skin infections, where it is often used to treat or prevent infections caused by this organism. Additionally, its action against Streptococcus species makes it useful in various dermatological conditions where both Staphylococcus and Streptococcus may be implicated.

Other options provided represent organisms that are either not primarily targeted by mupirocin or are resistant to its effects. For instance, while MRSA (methicillin-resistant Staphylococcus aureus) is included in the fourth choice, mupirocin’s primary comparative effectiveness is often highlighted against MSSA and Strep, reinforcing the selection of the latter as the most appropriate answer.