Kaptroban Mechanism of Action

Pharmacology: Mechanism of Action: Mupirocin is an RNA synthetase inhibitor antibacterial.
Pharmacokinetics: Only very small amounts of topically applied mupirocin are absorbed into the systemic circulation where it is rapidly metabolised to monic acid which is excreted in the urine.
Microbiology: Antimicrobial Action: Mupirocin is an antibacterial that inhibits bacterial protein synthesis by binding to isoleucyl transfer RNA synthetase. It is mainly bacteriostatic at low concentrations, although it is usually bactericidal in the high concentrations achieved by topical application to the skin. At these concentrations it may have some activity against organisms reported to be relatively resistant to mupirocin in vitro.
It is mainly active against Gram-positive aerobes. Most strains of staphylococci (including methicillin-resistant and multiply-resistant Staphylococcus aureus) and streptococci are susceptible in vitro, although the enterococci are relatively resistant. Mupirocin is also active against Listeria monocytogenes and Erysipelothrix rhusiopathiae. The Gram-negative organisms are generally insensitive, but Haemophilus influenzae, Neisseria spp. and a few others are sensitive. Anaerobic organisms, both Gram-positive and Gram-negative, are generally resistant, and activity against fungi is low. Mupirocin is more active in vitro at acid pH than in alkaline conditions.
Naturally resistant strains of Staphylococcus aureus occur rarely but resistance, including high-level plasmid-mediated transferable resistance, has emerged, particularly during long-term use. There has been some concern that inappropriate prescribing of mupirocin has led to this steadily increasing resistance.