Murocin Mechanism of Action

Pharmacotherapeutic group: Antibiotics and chemotherapeutics for dermatological use. ATC code: D06AX09.
Pharmacology: Pharmacodynamics: Murocin contains mupirocin which is a novel antibiotic produced through fermentation by Pseudomonas fluorescens. Mupirocin inhibits isoleucyl transfer-RNA synthetase, thereby arresting bacterial protein synthesis.
Mupirocin has bacteriostatic properties at minimum inhibitory concentrations and bactericidal properties at the higher concentrations reached when applied locally.
Mechanism of Resistance: Low-level resistance in staphylococci is thought to result from point mutations within the usual staphylococcal chromosomal gene (ileS) for the target isoleucyl tRNA synthetase enzyme. High-level resistance in staphylococci has been shown to be due to a distinct, plasmid encoded isoleucyl tRNA synthetase enzyme.
Intrinsic resistance in Gram negative organisms such as the Enterobacteriaceae could be due to poor penetration of the outer membrane of the Gram negative bacterial cell wall.
Due to its particular mode of action, and its unique chemical structure, mupirocin does not show any cross-resistance with other clinically available antibiotics.
Microbiological Susceptibility: The prevalence of acquired resistance may vary geographically and with time for selected species, and local information on resistance is desirable, particularly when treating severe infections. As necessary, expert advice should be sought when the local prevalence of resistance is such that the utility of the agent in at least some types of infection is questionable.
Commonly susceptible species: Staphylococcus aureus*; Streptococcus pyogenes*; Streptococcus pyogenes*; Streptococcus spp. (βhaemolytic, other than S. pyogenes).
Species for which acquired resistance may be a problem: Staphylococcus spp., coagulase negative.
Inherently resistant organisms: Corynebacterium spp.; Micrococcus spp.
* Activity has been satisfactorily demonstrated in clinical studies.
Pharmacokinetics: After topical application of Mupirocin ointment, Mupirocin is only very minimally absorbed systemically and that which is absorbed is rapidly metabolised to the antimicrobially inactive metabolite, monic acid. Penetration of Mupirocin into the deeper epidermal and dermal layers of the skin is enhanced in traumatised skin and under occlusive dressings.
Elderly patients: No restrictions unless there is evidence of moderate or severe renal impairment. (See Precautions.)