Gallium ointment shows promise in treating lower limb wounds in horses

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A compound containing a semi-metallic element has shown promise in helping to heal wounds on the lower limbs of horses.

Shauna Lawless and her colleagues at Texas A&M University reported benefits from the use of a topical ointment containing 0.5% gallium maltolate.

The ointment resulted in more rapid reduction in wound size, reduced formation of exuberant granulation tissue, and reduced the bioburden Staphylococcus aureus when compared to a similar ointment base without gallium maltolate.

Representative images of treated and untreated wounds at each time point, from initial injury and weekly thereafter. Images: Lawless et al.

The researchers, writing in the open-access journal PLOS ONE, note that lower limb wounds are common in horses and their healing is fraught with complications due to equine anatomy, the prevalence of infection, and challenges with wound management.

Gallium is a semi-metallic element shown to possess antimicrobial properties and aid in wound healing in various preclinical models, but its effects have not been studied in equine wound healing.

For that reason, Lawless and her fellow researchers set out to compare healing rates between gallium-treated and untreated wounds in horses to discover whether the antimicrobial effects of gallium on wounds inoculated with S. aureus.

Their study, involving six horses, documented reduced healing times, a reduced bioburden, and less granular tissue in wounds treated with gallium maltolate when compared with untreated wounds.

“Gallium appeared to exert its beneficial effects via its well-described antimicrobial actions as well as by altering the expression of specific genes known to be involved in wound healing of horses and other animals.

“Specifically, gallium maltolate appeared to increase expression of transforming growth factor-β in both infected and uninfected wounds.”

The study team says further work is needed to document the effects of gallium on naturally occurring equine wounds and to compare its effects with other wound treatment options.

The findings, however, suggest gallium may be an attractive and new way of improving wound healing in the lower limbs of horses.

Gallium, they say, has been studied extensively as an antimicrobial agent. Its antimicrobial properties have been attributed to its similarities to ferric iron (Fe3+).

Gallium is therefore taken up by bacteria to be used in biological processes requiring Fe3+, including DNA synthesis, resulting in inhibition of bacterial replication and ultimately bacterial death.

However, the gallium maltolate ointment was also found to exert beneficial healing effects in non-infected wounds.

This, they said, indicates that antimicrobial effects of the gallium alone do not explain the mechanism by which wound healing was improved. It suggests the possibility of host-directed effects, which may relate to the level of cytokines present.

“Given the frequency with which horses incur wounds, inherent difficulties associated with wound healing on the distal limb of horses, and the increasing identification of multi-drug resistant bacteria associated with equine wounds, an inexpensive and effective wound care product that exerts both host effects and antimicrobial effects holds great promise.”

The full Texas A&M study team comprised Lawless, Noah Cohen, Sara Lawhon, Ana Chamoun-Emanuelli, Jing Wu, Andrés Rivera-Vélez, Brad Weeks and Canaan Whitfield-Cargile.

Lawless SP, Cohen ND, Lawhon SD, Chamoun-Emanuelli AM, Wu J, Rivera-Vélez A, et al. (2020) Effect of gallium maltolate on a model of chronic, infected equine distal limb wounds. PLoS ONE 15(6): e0235006.

The study, published under a Creative Commons License, can be read here

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