A first report on the microbial colonisation of the equine oesophagus.

The research article delves into the microbial colonization of the epithelium of the equine oesophagus, with a dominant presence of bacteria and lesser amounts of fungi, identified through techniques like cryo-SEM, TEM, and microbiological differentiation.

Techniques Used for Study

• The researchers used cryo-scanning electron microscopy (Cryo-SEM), standard and high resolution transmission electron microscopy (TEM), and glycoconjugate histochemistry to visualize and study the microbial colonization.
• The tool of microbiological differentiation was used to distinguish and identify the various microorganisms present.

Microbial Colonization of the Equine Oesophagus

• The study found the equine oesophagus to be primarily colonised by bacteria, forming a one-layer system attached to and embedded in mannose/mannan substances covering the exterior portion of corneal cells.
• The numbers of bacteria varied between 5600 to 7200 per mm square in the central part of the oesophagus. Fungal presence was noted to be less than 1% compared to the amount of bacteria.
• These bacteria were found amongst the compact stratum corneal cells, which revealed numerous short protrusions sometimes part of desmosomal contacts but primarily projecting into distinct intercellular spaces, containing a mixture of acid and neutral glycoconjugates.
• The outermost corneal cells exhibited intact mitochondria and cytoplasmic vesicles, and a number of short cell processes going towards the oesophageal lumen; that is into the glycoconjugate layers on the surface of the oesophagus.

Most Frequent Bacteria Genera and Observed Fungi

• Among the bacteria present, the study indicated the presence of a permanent mucosal flora, dominated by facultative and obligate anaerobic species.
• The most frequently isolated and present in highest numbers were streptococci, Prevotella spp., Fusobacterium spp. and Actinobacillus equuli.
• Only two groups of Enterobacteriaceae (Escherichia coli, Pantoea spp.) were regularly located, and their quantity was less than that of the other bacterial groups mentioned above.
• Fungi were predominantly yeasts, however, they were identified very rarely.