Commensal and pathogenic bacteria of the respiratory tract of bats from Catalonia, North-Eastern Spain.

Bats host a diverse range of commensal and potentially pathogenic microorganisms , yet bacterial infections remain underrepresented in bat health research. This study investigated the diversity of bacteria of the respiratory tract in bats from Catalonia, North-Eastern Spain, including free-ranging individuals and those admitted to a wildlife rehabilitation centre. Oropharyngeal swabs were collected and processed for microbiological analysis from 182 apparently healthy bats belonging to 14 species, and from 28 bats admitted to the wildlife rehabilitation centre. Additionally, necropsy, microbiological and histopathological investigation were performed on 30 deceased individuals. A total of 394 bacterial isolates were recovered and identified by 16S rRNA gene sequencing, selected strains were further characterized by ERIC-PCR and phylogenetic analysis. The genus Vespertiliibacter, within the Pasteurellaceae family, was the most detected in apparently healthy bats and was significantly more prevalent in this group (59.3%) than in rehabilitated bats (35.7%, p=0.024). By contrast, Pasteurella multocida subsp. septica was only identified in two cases of fatal pneumonia and sepsis in Pipistrellus kuhlii. Enterobacteriaceae were significantly more prevalent in rehabilitated bats (46.4%) than in free-ranging individuals (10.4%, p < 0.001). These findings expand current knowledge on the upper respiratory microbiota of bats, support the role of P. multocida as a primary pathogen in this group, and highlight the presence of bacterial species of potential clinical relevance for bat health. • First large-scale survey of culturable bat respiratory bacteria in NE Spain. • Vespertiliibacter spp. dominates the oropharyngeal microbiota of healthy bats. • Pasteurella multocida linked to fatal pneumonia and septicemia in bats. • Higher load of opportunistic Enterobacteriaceae in bats at rehabilitation facility.