Prevalence of organisms described as Actinobacillus suis or haemolytic Actinobacillus equuli in the oral cavity of horses. Comparative investigations of strains obtained and porcine strains of A. suis sensu stricto.

This study found evidence that certain bacterial strains in horses’ mouths, previously classified as Actinobacillus suis or hemolytic variants of Actinobacillus equuli, might constitute a separate group of organisms. These distinctions are supported by DNA analysis. However, final classification and naming awaits further genetic studies. These bacterial strains appear to be a regular part of the oral flora in horses.

Understanding the Research

• This research investigated bacteria known as Actinobacillus suis and hemolytic variants of Actinobacillus equuli in the oral cavity of horses. These organisms were earlier believed to be the same or similar but the current study suggests they may constitute a separate group of organisms, tentatively named as taxon 11.
• The study was significant because it calls for a reevaluation of our understanding of these bacteria, which may have implications for equine health and disease.

Analyzing Bacterial Strains

• The study identified four different subtypes (biovars) within the proposed group, taxon 11.
• To confirm the classification of these biovars, DNA analysis was used. In particular, the study conducted selected DNA:DNA hybridizations, a scientific technique used to compare the genetic material of different organisms.
• This analysis supported the classification of the mannitol positive biovar 2 of taxon 11 as distinct from porcine A. suis, a similar bacteria found in pigs.

Future Research Directions

• Despite the findings, the study concluded that the final taxonomical positioning of taxon 11 cannot be decided until more detailed genetic studies are done. These would need to include all biovars of taxon 11.
• Similarly, a proposed species name for this group of organisms has not been suggested, as this too should await more comprehensive genetic research.

Bacteria in Horses’ Mouths

• Aside from the taxonomical implications, the research also found indications that strains identified as taxon 11 could be a part of the normal bacterial flora in the oral cavity of horses.
• This is of interest to equine health because changing our understanding of what bacteria are ‘normal’ in a horse’s mouth could affect how we approach equine oral healthcare and disease prevention.