Mupirocin

Topical antibacterials
Topical antibacterials

A topical antibiotic that blocks a bacterial tRNA-loading enzyme. Used for impetigo and to clear Staphylococcus aureus (including MRSA) from the nose.

Updated Nov 1, 2026

Quick facts

Group: Topical antibacterials
Target: Bacterial isoleucyl-tRNA synthetase (IleRS)
Used for: Impetigo caused by S · Clearing nasal S
Key effects: Burning · Itching · Local irritation
Monitor: Clinical response within a few days
ATC: D06AX09

No doses: the clinician sets them by the current guideline.

Mechanism of action

Bacterial isoleucyl-tRNA synthetase (IleRS)Mupirocin

The figure shows Staphylococcus aureus isoleucyl-tRNA synthetase with its tRNA and mupirocin bound in the active site.

Target in 3D: Bacterial isoleucyl-tRNA synthetase (IleRS). PDB structure 1FFY (RCSB PDB, public domain). View the structure at RCSB PDB

Mupirocin is made by the bacterium Pseudomonas fluorescens. It binds reversibly and specifically to bacterial isoleucyl-tRNA synthetase, the enzyme that loads isoleucine onto its tRNA. Without charged tRNA-Ile the ribosome stalls and protein synthesis stops; at the concentrations reached on the skin the effect is bactericidal. It acts on S. aureus (including MRSA) and Streptococcus pyogenes but hardly on normal skin flora or anaerobes, and because its target is unique it shows no cross-resistance with other antibiotic classes.

Mupirocin binds bacterial isoleucyl-tRNA synthetase
Isoleucine cannot be loaded onto its tRNA
Protein synthesis stops in S. aureus and S. pyogenes
Bacteria die at the concentrations reached on the skin

Indications

Impetigo caused by S. aureus or S. pyogenes Impetigo →
Superficial bacterial folliculitis
Clearing nasal S. aureus carriage (nasal formulation), for example before surgery in known carriers Surgical site infection →

Adverse effects

Common

Burning, stinging or pain where it is applied
Itching
Local irritation or contact sensitisation

Contraindications

Hypersensitivity to mupirocin or any excipient

Key interactions

Polyethylene glycol ointment base on large open areas (kidney impairment): Polyethylene glycol can be absorbed and accumulate when the kidneys are impaired, so the ointment is not used there.

What is monitored

Clinical response within a few days; no improvement means re-evaluation
Spreading redness, fever or deeper infection that needs systemic treatment
Local irritation or sensitisation

Administration and safety

Topical use only; a thin layer on the affected area, which may be covered with gauze.
The skin ointment is not used in the nose, eyes or on other mucous membranes; a separate nasal ointment exists for nasal carriage.
Not used at intravenous cannula or central line sites: it can promote fungal infection and resistance.

Pregnancy and breastfeeding

Systemic absorption through intact skin is minimal, so exposure of the fetus or breastfed baby is expected to be very low; human data are limited.

Nursing care

Wash hands before and after applying.
Teach to use it only on the lesions it was prescribed for and for the planned course.
Report fever, spreading redness or diarrhoea.
In surgical patients who carry S. aureus, check that the planned nasal course and body wash were completed.

Pharmacokinetics

Absorption: No measurable systemic absorption through intact skin; it stays in the stratum corneum.
Distribution: Highly bound to proteins.
Metabolism: Any mupirocin that reaches the blood is quickly converted to inactive monic acid.
Elimination: Monic acid leaves mainly through the kidneys.

Test yourself

Think of the answer, then tap the question to see it.

Why does mupirocin show no cross-resistance with other antibiotic classes?

Its target, bacterial isoleucyl-tRNA synthetase, is not used by other classes.

How does high-level mupirocin resistance arise?

By acquiring a plasmid that encodes a different isoleucyl-tRNA synthetase (low-level resistance comes from mutations in the native enzyme).

Which surgical patients may receive nasal mupirocin, and why?

Known nasal carriers of S. aureus, to lower the risk of surgical site infection, often together with chlorhexidine body wash.

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Connections

← Back to the class: Topical antibacterials

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Mupirocin topical: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - MUPIROCIN ointment (DailyMed (U.S. National Library of Medicine), 2026); Global guidelines for the prevention of surgical site infection (World Health Organization, 2018); Insights into editing from an Ile-tRNA synthetase structure with tRNA(Ile) and mupirocin (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.