Antibiotics delivered by frog foam

Foam made by tiny frogs could be used to deliver antibiotics to help prevent infections, research involving the University of Strathclyde has found

At the Microbiology Society's Annual Conference in Liverpool, Strathclyde scientists Paul Hoskisson and Sarah Brozio unveiled their study showing how the foam made by Trinidadian frogs could have important health applications.

Foams are unusual in nature and are typically made of inactivated proteins, yet this frog foam is stable and compatible with human cells making it usable for pharmaceutical applications.

Hoskisson, who led the research team, said: "While foams like these are a long way from hitting the clinic, they could help in burns and wound treatment providing support and protection for healing tissue and delivering drugs at the same time – all from a humble little frog."

While mating, Tungara frogs (Engystomops pustulosus) release a protein cocktail that they beat into a foam with their back legs. The miniature frogs lay their eggs in these foam nests to protect them from disease, predators and environmental stresses.

The Strathclyde academics analysed foam from Tungara frogs and found it is highly stable, and capable of taking up drugs and releasing them at a stable rate.

The group showed the foam can release model dyes at a steady rate over a period of 72-168 hours, while foam loaded with the antibiotic vancomycin was shown to prevent in vitro growth of the pathogenic bacterium Staphylococcus aureus for a period of 48 hours.

The foam proteins were also tested in vitro against Keratinocytes, a type of skin cells, for 24 hours. These cells were still alive and viable after 24 hours of exposure, demonstrating that the foam is not toxic to human cells.

Brozio said: “Foams are usually very short-lived so they're not considered for long term drug release, even though they have great potential for topical treatments.

"This foam comes from a tiny frog and yet offers us a whole new approach that could prevent wound infections, and with increasing antibiotic resistance it's important that all new tactics are explored."

Currently, the team have engineered E. coli bacteria to produce two of the foam's protein constituents, including Ranaspumin-2, which on its own produces a short-lived foam that is also non-toxic to human cells.

The researchers are working to produce a completely synthetic form of the foam that is as stable as the frog-produced version.

The group, in collaboration with Dimitrios Lamprou, also at Strathclyde, envisage that the foam's long-lasting, durable characteristics could be used to treat severe burns, which frequently become infected and require the use of intravenous antibiotics.