Mupirocin

Mupirocin (aka pseudomonic acid) is a topical agent used to eliminate Staphylococcus aureus from the nasal passage. Mupirocin is nat urally  prod uced by Pseudomonas fluorescens.

Mupirocin has activity against a wide range of Gram-postive bacteria (including Staphylococus (MSSA and MRSA) and Streptococcus) and moderate activity against Gram-negatives.

Mupirocin reversibly binds to bacterial isoleucyl transfer RNA synthase. This prevents protein and RNA synthesis.

Mupirocin is commercially available in a polyethylene glycol base (which has antibacterial activity itself) as 'Bactroban'. Bactroban isn't recommended for intranasal use due to occurence of occasional local discomfort. In 1986, Casewell and Hill noted that mupirocin in a paraffin base does not appear to cause this discomfort.

In 1989, following a 1986 RCT by Casewell and Hill with healthy healthcare workers, a Belgium group Boelaert et al conducted an RCT comparing the effectiveness of calcium mupirocin ointment to placebo (applied 3X per day for 2 weeks and then 3x per week for nine months) in carriers of S. aureus from a haemodialysis unit.

Side Effects
In the 1986 RCT by Casewell and Hill (involving 32 healthy participants), no side-effects to mupirocin ointment were reported (applied 4x/day for 5 days). An increase in nasal secreation was observed (in both the placebo and control ointment groups).

Resistance
Although high- and low- level resistance to mupirocin has been reported, resistance is rare.