Characterization of the bacterial ocular surface microbiota of European bison (Bison bonasus) and their association with infectious keratoconjunctivitis

Numerous cases of infectious keratoconjunctivitis (IKC) have been recently observed in European bison in Poland. The present study aimed to identify the ocular surface microbiota of European bison and determine if bacterial communities differed between animals with and without IKC. Ocular swabs were collected from the conjunctiva and cornea of 57 European bison with IKC and 30 healthy animals, from southern and northeastern Poland. Swabs were cultured on Columbia Agar and incubated. Bacterial isolates were identified using MALDI-TOF MS. In the eyes of European bison, 44 bacterial genera and 88 species were detected. The most common were opportunistic bacteria, including Acinetobacter spp., Pseudomonas spp., Aeromonas spp., Pantoea spp., Staphylococcus spp., Serratia spp., Enterococcus spp., and Lelliottia spp. The prevalence of bacteria of the genera Aeromonas, Serratia, and Lelliottia increased together with the severity of ocular changes. These genera were detected significantly more often in European bison with IKC compared to healthy animals, whereas bacteria of the genus Pantoea were identified more often in animals without ocular lesions. None of the isolated bacteria appeared to be a primary etiological agent of IKC in European bison. To the best of our knowledge, this is the first study describing ocular surface microbiota in European bison.