Mupirocin

Mupirocin (pseudomonic acid A, or Bactroban) is an antibiotic originally isolated from Pseudomonas fluorescens. It is used topically, and is primarily effective against Gram-positive bacteria.

It has a unique mechanism of action, which is selective binding to bacterial isoleucyl-tRNA synthetase, which halts the incorporation of isoleucine into bacterial proteins. Because this mechanism of action is not shared with any other antibiotic, mupirocin has few problems of antibiotic cross-resistance, and is useful in the treatment of methicillin-resistant Staphyolococcus aureus (MRSA), which is a significant cause of death in hospitalized patients who have received systemic antibiotic therapy. It is suggested, however, that mupirocin not be used for extended periods of time, or indiscriminately, as resistance does develop, and could, if it becomes widespread, destroy mupiricin's value as a treatment for MRSA.