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# Topical antibacterials

Antibiotics applied to the skin for superficial infections such as impetigo, and to protect burns. Short courses limit resistance.

Updated Nov 1, 2026

## What they are

Antibacterials made to act on the skin surface: mupirocin for impetigo and for nasal carriage of Staphylococcus aureus, fusidic acid for superficial skin infections, retapamulin and ozenoxacin for impetigo, and silver sulfadiazine for burns. Deeper or spreading infections (cellulitis, abscess) need systemic antibiotics instead.

## Mechanism of action

The agents differ: mupirocin blocks isoleucyl-tRNA synthetase, retapamulin binds a unique site on the 50S ribosomal subunit, and silver sulfadiazine releases silver that damages the bacterial membrane, wall and DNA. Applied locally they reach high concentrations at the infected surface with little systemic exposure.

Target: Bacterial protein synthesis (isoleucyl-tRNA synthetase, ribosome) or bacterial membrane and DNA (silver)

## Key points

- Topical antibiotics are for localised superficial infection; cellulitis, abscess and fever need systemic treatment.
- Antibiotic ointment on clean surgical wounds does not lower infection rates and adds contact dermatitis and resistance.
- High-level mupirocin resistance is increasingly reported in S. aureus, more often in MRSA.
- Silver sulfadiazine is a sulfonamide: avoided near term in pregnancy and in newborns (kernicterus), and watched for leukopenia.
- Nasal mupirocin (with or without chlorhexidine body wash) is used to clear S. aureus carriage before some surgery.

## Drugs in this class

- [**Mupirocin** A topical antibiotic that blocks a bacterial tRNA-loading enzyme. Used for impetigo and to clear Staphylococcus aureus… Bacterial isoleucyl-tRNA synthetase (IleRS)](https://durgical.com/en/pharmacology/mupirocin/)
- [**Silver sulfadiazine** A silver-sulfonamide cream that keeps deep burns from getting infected. Avoided late in pregnancy and in babies under… Bacterial cell membrane, cell wall and DNA (silver ions)](https://durgical.com/en/pharmacology/silver-sulfadiazine/)
- [**Bacitracin** A polypeptide antibiotic ointment that helps keep minor cuts, scrapes and burns from becoming infected; injected forms… Bacterial cell-wall synthesis (the lipid carrier that moves wall building blocks)](https://durgical.com/en/pharmacology/bacitracin/)
- [**Retapamulin** A topical pleuromutilin antibiotic ointment for impetigo caused by Staphylococcus aureus or Streptococcus pyogenes… Bacterial 50S ribosomal subunit (peptidyl transferase centre)](https://durgical.com/en/pharmacology/retapamulin/)

## Others in the class

- fusidic acid
- retapamulin
- ozenoxacin
- bacitracin
- mafenide

## Test yourself

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

## Which enzyme does mupirocin inhibit?

Bacterial isoleucyl-tRNA synthetase, so isoleucine cannot be loaded onto its tRNA and protein synthesis stops.

## Why is silver sulfadiazine avoided in newborns in their first two months?

It is a sulfonamide and can raise the risk of kernicterus.

## When is a topical antibiotic not enough for a skin infection?

When the infection is deep or spreading (cellulitis, abscess), widespread, or accompanied by fever: systemic antibiotics are needed.

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

Sources: [DailyMed - MUPIROCIN ointment](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a822d44d-c651-406c-a2b9-aa8fbe8f89ce) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - SILVER SULFADIAZINE cream](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b4d6694f-2b0a-4d64-9e05-2fef6d8e60d9) (DailyMed (U.S. National Library of Medicine), 2026); [Global guidelines for the prevention of surgical site infection](https://www.who.int/publications/i/item/9789241550475) (World Health Organization, 2018).

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Representative model, for educational purposes only.

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