Effects of Actinobacillus equuli culture supernatants on equine neutrophil functions and survival.

This research assesses the impact of Actinobacillus equuli culture supernatants on the behaviour and lifespan of neutrophils in both foal and adult horse samples. The study found that exposure to these bacterial culture supernatants led to a decrease in total granulocytes and light emission, suggesting the presence of leukotoxic bacterial products in the supernatants.

Actinobacillus Equuli and Equine Neutrophils

• The study involves the bacterial species Actinobacillus equuli, often isolated from infections in equines.
• The focus is given to equine neutrophils, a type of white blood cell. Like all granulocytes, neutrophils contain granules filled with potent biochemicals that help combat infections.
• These neutrophils were exposed to culture supernatants from clinical isolates of A. equuli.

Assessment of Neutrophil Functions

• To examine the effects of the supernatants, the researchers studied two primary functions of neutrophils: phagocytic capacity (the cell’s ability to engulf and destroy foreign particles) and respiratory burst (the rapid release of reactive oxygen species a part of the immune response).
• The analysis was performed using flow-cytometry for phagocytic capacity and a chemiluminescence assay for assessing respiratory burst.

Impact of A. Equuli Culture Supernatants

• The exposure to A. equuli culture supernatants resulted in a notable decrease in the total number of granulocytes and light emission, indicating the presence of leukotoxic, or white-cell destroying, bacterial products in the supernatants.
• When neutrophils were exposed to supernatants from a specific haemolytic isolate of A. equuli, a more decrease in the total number of granulocytes and light emission was seen, indicating a higher number or more potent leukotoxic metabolites.

Significance of the Findings

• These results suggest A. equuli culture supernatants negatively affect the survival rate of neutrophils but do not significantly inhibit the neutrophils’ functions.
• The findings can illuminate more about the pathogenicity of A. equuli in equines and might help in future studies aimed at finding suitable treatments for such bacterial infections.