Microbiology of equine wounds and evidence of bacterial biofilms.

This research study examines the microbiology of horse wounds, with a particular focus on bacterial biofilms, types of microbial communities that are notoriously resistant to treatment. The study highlights the complex diversity of bacteria in these wounds, confirms the existence of biofilms, and infers that these biofilms likely explain why many equine wounds become chronic and struggle to heal.

Research Methodology

• The researchers collected 13 8-mm wide tissue samples from chronic wounds on 18 horses. The diversity and structure of the bacterial communities in these samples were then studied.
• A histological staining method was used to visually observe the samples for biofilms – structural colonies of bacteria that can lodge in tissue.
• A further 51 wound and control skin sites were sampled with sterile swabs. Control sites were chosen as the uninjured regions on the opposite side of the horse as the wound, at a similar anatomical location.
• The isolated bacteria were cultured both in the presence (aerobically) and absence (anaerobically) of oxygen, to provide further details on the nature and diversity of the bacterial populations.
• The bacteria’s ability to form biofilms was determined with a standard assay test using crystal violet, a common staining agent.

Key Findings

• Following the staining process, bacteria biofilms were seen to be present in 8 of the 13 (61.5%) equine wounds analysed.
• The researchers identified 340 unique bacterial isolates from all the wound and skin samples studied. The most commonly isolated species were Pseudomonas aeruginosa from wound samples and Enterococcus faecium from the skin samples.
• Alongside these, Staphylococcus was the most commonly isolated bacterial genus across both types of samples.
• The study found that bacteria cultured from both the chronic and acute wounds had a significantly higher potential to form biofilms than bacteria from skin samples.

Significance of the Study

• This study provides preliminary evidence of bacterial biofilms existing within chronic horse wounds, backing the hypothesis of their role in making these wounds resistant to healing.
• It calculates a high level of microbial diversity in these wounds, detailing bacterial species that may be crucial in understanding the treatment (or lack thereof) of such wounds.
• The research underlines the welfare and economic concern of non-healing limb wounds in horses, and the importance of understanding the underlying factors to inform future treatment strategies. The aim is to increase healing rates, decrease costs, and alleviate the suffering associated with persistent equine wounds.