Retapamulin - How a mushroom fights bacteria

Pleurotus mutilus (also called Clitopilus scyphoides) is delicate cream-coloured edible ectomycorrhizal gilled mushroom that makes an antibacterial compound quite aptly called pleuromutilin.

Like many other antibiotics, pleuromutilin and its lab-born derivatives carry out bacterial genocide by binding to bacterial ribosomes and inhibiting protein synthesis (which is what ribosomes do). This is accomplished by their binding to a domain of 23S rRNA (ribosomes = protein + rRNA), not bound by any other type of similar-acting antibiotic, and directly preventing the binding of the components (peptidyl transferase and amino acid-carrying tRNAs) binding necessary for the formation of proteins. Their unique site of action means that cross-resistance to other antibiotics is non-existent, making them effective against things like MRSA.

Retapamulin (Altabax, Altargo) is a topical semisynthetic pleuromutilin derivative formulated as an ointment and indicated for the treatment of superficial bacterial skin infections such as impetigo and those resulting from wounds. It works well against Gram-positive bacteria, but not much else. Other pleuromutilins that are out there include tiamulin and valnemulin, which are both used by veterinarians to treat infected pigs.

- Yan K, Madden L, Choudhry AE, Voigt CS, Copeland RA, Gontarek RR. Biochemical characterization of the interactions of the novel pleuromutilin derivative retapamulin with bacterial ribosomes. Antimicrob Agents Chemother. 2006 Nov;50(11):3875-81. Epub 2006 Aug 28.
- Yang LP, Keam SJ. Retapamulin: a review of its use in the management of impetigo and other uncomplicated superficial skin infections. Drugs. 2008;68(6):855-73.