Mupirocin, sold as Bactroban, is an antibiotic ointment or cream used on skin infections such as impetigo and for clearing staph bacteria from the nose.1MedlinePlus. Mupirocin topical: MedlinePlus Drug Information It is one of the few antibiotics that still works on staph strains resistant to many other drugs, including MRSA.2PubMed. Characterization of the mupirocin biosynthesis gene cluster from Pseudomonas fluorescens NCIMB 10586 It is used only on the skin, because the body breaks it down too quickly for it to work as a pill or injection.3PubMed. Liposomal mupirocin holds promise for systemic treatment of invasive Staphylococcus aureus infections
How Mupirocin Stops Bacteria
Mupirocin comes from a soil bacterium, Pseudomonas fluorescens.4PubMed. Characterization of the mupirocin biosynthesis gene cluster from Pseudomonas fluorescens NCIMB 10586 Bacteria build their proteins as a chain of building blocks, added one at a time, and each block has its own loading enzyme. Mupirocin shuts down the enzyme that loads the block isoleucine.5PubMed Central. Mechanism of mupirocin transport into sensitive and resistant bacteria It does this by competing with isoleucine for the enzyme’s slot, so the loader stays jammed and the chain stops growing.6PubMed. Characterization of the mupirocin biosynthesis gene cluster from Pseudomonas fluorescens NCIMB 10586 A bacterium that can’t finish its proteins can’t make the enzymes and wall parts it needs, so it stops growing and dividing rather than simply dying on contact.
The bacterial version of this enzyme is different enough from ours that mupirocin targets bacteria selectively.7PubMed Central. Mupirocin: A Useful Antibiotic for Methicillin-Resistant Staphylococcus aureus Decolonization: A Narrative Review No other antibiotic class works this way, so resistance to other antibiotics doesn’t carry over to mupirocin.8PubMed Central. Mupirocin: A Useful Antibiotic for Methicillin-Resistant Staphylococcus aureus Decolonization: A Narrative Review
Which Bacteria Mupirocin Works Against
Mupirocin is highly active against staph and strep, the main causes of skin infections.9PubMed Central. Antibacterial activity of mupirocin (pseudomonic acid), a new antibiotic for topical use Nearly all staph samples tested, including strains resistant to several drugs, were stopped by very small amounts.10PubMed Central. Antibacterial activity of mupirocin (pseudomonic acid), a new antibiotic for topical use MRSA is usually included.11PubMed. Characterization of the mupirocin biosynthesis gene cluster from Pseudomonas fluorescens NCIMB 10586
It does much less against most rod-shaped gram-negative bacteria, such as E. coli, and against bacteria that live without oxygen.12PubMed Central. Antibacterial activity of mupirocin (pseudomonic acid), a new antibiotic for topical use Those bacteria have a tough outer wall and pumps that push the drug out before it builds up.13ACS Infectious Diseases. The Hybrid Antibiotic Thiomarinol A Overcomes Intrinsic Resistance in Escherichia coli Using a Privileged Dithiolopyrrolone Moiety
It does nothing for fungal rashes such as ringworm, for eczema, or for cold sores caused by a virus, because it only acts on bacteria. A rash that looks infected but doesn’t improve within a few days may be caused by something mupirocin doesn’t cover, or may not be an infection at all, so it should be rechecked.
Using Mupirocin for Impetigo and Skin Infections
Impetigo is a contagious skin infection, common in children, that forms honey-colored crusts. Antibiotic creams clear it far better than a placebo ointment.14PubMed Central. A systematic review and meta-analysis of treatments for impetigo Mupirocin works as well as antibiotic pills for staph and strep impetigo, with fewer side effects.15PubMed. Review of mupirocin ointment in the treatment of impetigo It also performs about the same as fusidic acid, another antibiotic cream.16PubMed Central. A systematic review and meta-analysis of treatments for impetigo
A common course is twice a day for 5 days.17PubMed Central. Topical Antibiotic Treatment in Dermatology Some reviews recommend up to 7 days.18PubMed Central. A systematic review and meta-analysis of treatments for impetigo
Before each application, gently wash the sores with soap and water, remove loose crust if it comes away easily, and pat the skin dry. Spread a thin layer over the sores and a little of the skin around them; more than that does not work better. You may cover the area with gauze if clothing will rub it or you or your child might pick at it, but covering is optional. Wash your hands afterward so you don’t carry the bacteria to other skin or other people. Crusts often fade before every bacterium is gone, so stopping early can let the infection return.
Cream isn’t always enough. Widespread sores, fever, or feeling unwell usually call for pills, and sores that keep spreading after a few days of cream need a recheck. Children can usually return to school once they have been treated for a day, or as their doctor advises.
Mupirocin in the Nose Before Surgery or in Hospital
Many people carry staph harmlessly inside their nose. Before surgery, clearing it from the nose aims to stop the bacteria reaching the wound. Mupirocin is the most studied product for this. It lowers wound infections after joint and bone surgery, with somewhat weaker evidence for heart surgery.19PubMed. Nasal decolonization: What antimicrobials and antiseptics are most effective before surgery and in the ICU It works best paired with chlorhexidine body washes in people found to carry staph.20PubMed. Prevention of Surgical Site Infections: Decontamination With Mupirocin Based on Preoperative Screening for Staphylococcus aureus Carriers or Universal Decontamination? Some hospitals test the nose first and treat only carriers; others treat everyone.
A typical routine puts a small amount, about the size of a match head, just inside each nostril, commonly twice a day for about 5 days, though your hospital’s instructions rule. Afterward, press the sides of the nose together and gently massage so the ointment spreads along the inner surface. Chlorhexidine body washes are often scheduled on the same days, so check whether you need both. The routine usually ends close to the surgery date, so follow the dates you were given rather than starting early.
The evidence has limits. Studies pooled across many kinds of surgery have not all shown a clear benefit from mupirocin alone.21PubMed Central. Nasal decolonization of Staphylococcus aureus and the risk of surgical site infection after surgery: a meta-analysis In intensive care, it lowers how often staph turns up in patient samples.22PubMed. Nasal decolonization: What antimicrobials and antiseptics are most effective before surgery and in the ICU In newborn intensive care, it cleared staph in about 94% of treated babies, but many carried it again within 2 to 3 weeks.23PubMed Central. Mupirocin for Staphylococcus aureus Decolonization of Infants in Neonatal Intensive Care Units
Why Mupirocin Only Comes as an Ointment or Cream
Taken by mouth or injected, mupirocin is quickly broken down.24DailyMed. Mupirocin It becomes monic acid, which has no effect on bacteria and leaves through the kidneys.25DailyMed. Mupirocin A pill’s dose would be gone before reaching the skin, so mupirocin can only reach high levels where it is applied.26PubMed. Liposomal mupirocin holds promise for systemic treatment of invasive Staphylococcus aureus infections Very little reaches the bloodstream from intact skin, so whole-body side effects are uncommon.27PubMed. Liposomal mupirocin holds promise for systemic treatment of invasive Staphylococcus aureus infections
That means it treats only the skin or nose lining it touches. It won’t help an infection that has spread beneath the skin or elsewhere in the body, and deep, swelling, or fast-spreading infections need a different antibiotic that can travel through the blood.
Side Effects and Who Should Be Careful
Burning, stinging, or pain occurs in about 1.5 in 100 users, and itching in about 1 in 100.28U.S. Food and Drug Administration. BACTROBAN (mupirocin) ointment, for topical use If you get a rash suggesting allergy or severe irritation, stop and contact your prescriber.29U.S. Food and Drug Administration. BACTROBAN (mupirocin) ointment, for topical use In babies, mild rashes, usually around the bottom, were more common with treatment.30PubMed Central. Mupirocin for Staphylococcus aureus Decolonization of Infants in Neonatal Intensive Care Units
The skin ointment is made with polyethylene glycol, which can be absorbed through open wounds and damaged skin.31U.S. Food and Drug Administration. BACTROBAN (mupirocin) ointment, for topical use People with moderate or severe kidney disease should not use it on large raw areas.32U.S. Food and Drug Administration. BACTROBAN (mupirocin) ointment, for topical use If you have kidney problems, tell the prescriber before treating big raw areas or burns so they can pick a different product.
The nasal version uses a paraffin base because the original base irritated the nose.33Advances in Microbiology. Eradication of Staphylococcus aureus and MRSA in the Nares: A Historical Perspective of the Ecological Niche, with Suggestions for Future Therapy Considerations The skin and nasal ointments are therefore different products, so use the one prescribed for the place you are treating, and don’t put the skin ointment inside the nose. Keep either one out of your eyes, and rinse with water if some gets in.
When Mupirocin Stops Working, Resistance
Resistance comes in two forms. In low-level resistance, the bacteria’s own loading enzyme has a small change, so mupirocin grips it less tightly.34PubMed Central. Mutations affecting the Rossman fold of isoleucyl-tRNA synthetase are correlated with low-level mupirocin resistance in Staphylococcus aureus In hospital staph samples, one specific change caused about 94 to 95% of low-level cases.35PubMed Central. Chronicity of high and low level mupirocin resistance in Staphylococcus aureus from 30 Indian hospitals
High-level resistance comes from an extra backup enzyme gene that does the same job and that mupirocin can’t block, so the drug is bypassed.36PubMed Central. First Report of a Methicillin-Resistant, High-Level Mupirocin-Resistant Staphylococcus argenteus High-level resistance can make treatment fail.
The backup gene sits on a shared loop of DNA that bacteria can pass to each other.37PubMed Central. In vivo transfer of high-level mupirocin resistance from Staphylococcus epidermidis to methicillin-resistant Staphylococcus aureus associated with failure of mupirocin prophylaxis It has jumped from harmless skin staph to MRSA in a patient, causing mupirocin prevention to fail.38PubMed Central. In vivo transfer of high-level mupirocin resistance from Staphylococcus epidermidis to methicillin-resistant Staphylococcus aureus associated with failure of mupirocin prophylaxis Because of this, resistance can spread between staph strains even when no one used mupirocin on them. In hospital MRSA samples, resistance rates have ranged from about 1.5% to 9% depending on the hospital.39Antimicrobial Stewardship & Healthcare Epidemiology. The impact of hospital wide measures to reduce mupirocin resistance among methicillin-resistant <i>Staphylococcus aureus</i> in a Singapore hospital
Heavy hospital use pushes resistance up, and cutting back lets it fall.40PubMed Central. Antimicrobial Stewardship Lessons From Mupirocin Use and Resistance in Methicillin-Resitant Staphylococcus Aureus One hospital’s limits on use kept high-level resistance at about 2.5% of MRSA samples.41Antimicrobial Stewardship & Healthcare Epidemiology. The impact of hospital wide measures to reduce mupirocin resistance among methicillin-resistant <i>Staphylococcus aureus</i> in a Singapore hospital
You can help by using it only for the time prescribed, not keeping old tubes for future rashes, and not sharing it with family members. If a past course didn’t work, tell your prescriber.
Alternatives If Mupirocin Isn’t Right
Retapamulin is another ointment used for impetigo, also twice a day for 5 days.42PubMed Central. Topical Antibiotic Treatment in Dermatology In lab tests, it was active against mupirocin-resistant MRSA from children.43PubMed Central. Topical Antibiotic Treatment in Dermatology In children carrying mupirocin-resistant MRSA, it cleared the bacteria at one week, but the benefit had faded by one month.44PubMed Central. 568. A Randomized, Double-Blinded, Placebo-Controlled Trial of Retapamulin for Nasal and Rectal Decolonization of Mupirocin-Resistant Methicillin-Resistant Staphylococcus aureus Among Children Ozenoxacin barely enters the blood and works against mupirocin-resistant staph.45PubMed Central. Topical Antibiotic Treatment in Dermatology
A swab of the sore or nose can show whether the staph is resistant to mupirocin, which helps the prescriber choose a different cream. Fusidic acid, where it is available, works much like mupirocin for impetigo, though resistance to it also occurs. Antibiotic pills are chosen when impetigo is widespread or the infection is deep, since creams only treat the surface.
Chlorhexidine antiseptic washes can be used instead of antibiotics for clearing skin bacteria before surgery.46PubMed Central. Topical Antibiotic Treatment in Dermatology If you are found to carry mupirocin-resistant staph before surgery, an antiseptic plan with chlorhexidine washes may replace the nose ointment, so raise this with the surgical team.