Could platypus milk help beat antibiotic resistance?

In 2014, the World Health Organisation warned the international community of the threat of antibiotic resistance. Due to an excessive use of antibiotics – mostly fed to food-producing animals – bacteria are able to develop resistance, which they then transmit to the next generation of bugs, who can no longer be killed by available pharmaceuticals. As a result, diseases which have been treatable for years, thanks to Alexander Fleming’s discovery, are once again responsible for many deaths – killing approximately 5000 people in the UK each year.

In this critical situation, hope arises from new research being carried out on species which previously had no funding due to their insignificance. Australia’s wildlife is one of the areas of interest. A protein in platypus milk was found to have antibacterial properties by a team of Australian scientists from Deakin University, Victoria, in 2010. A recent paper published by Dr Janet Newman, from Australia’s national science agency CSIRO, identifies the functional groups of this protein enabling it to combat superbugs.

As indicated by crystallisation, the molecule is unique, and presents no similarity with any other known protein. Consequently, this constitutes a new field for researchers and scientist to explore! The monotreme lactation protein (MLP) includes a monomer of twelve helices, two short β-strands, and a deep fold which gives it the nickname “Shirley Temple,” after the famous American child star with curly hair from the 1930s. This discovery reinforces Newman’s belief that monotremes may be an unexploited source for identification of new proteins, with interesting properties such as antimicrobial activity. Dr Newman was not overly surprised by this as she states: “Platypus are such weird animals that it would make sense for them to have weird biochemistry”.

Ornithorhynchus anatinus and echidnas are indeed the only two mammals on earth which lay eggs. They are considered mammals because they feed their babies with milk similar to cows or humans. What could then explain their lactating proteins contain such antibiotic? Like no other mammals, the monotremes are unable to breastfeed their progeniture; instead they sweat milk, which is exposed to the outside environment and thus has the susceptibility of possibly becoming contaminated. This evolution of the platypus may be its defensive response for a safe and sterile delivery system of milk in order to protect the young from possible infection. The particular fold of the protein explains its “antibacterial properties against some of the nastier bugs you find in the environment but not against some bacteria found in the guts of the young”, Newman reports, after observing the molecule killing bacteria such as Staphylococcus aureus and Enterococcus faecalis.

Even though the platypus milk could lead to the creation of new antibiotic treatment against superbugs, drug discovery will take a long time before patients are offered new pharmaceuticals. Thus, it is still crucial to counter bacterial resistance to antibiotics by reducing the massive use of antibiotics worldwide. The promise of innovative antibiotics being developed against superbugs is a relief in the eventuality of a future ‘post-antibiotics era,’ but should not be taken for granted, as research is still required to understand the protein’s interactions before it can be commercialised as a treatment.