Abstract
Background: Bats are important reservoir hosts for numerous emerging pathogens with zoonotic potential. In Europe, 47 bat species have been recorded, 33 of which occur in Bulgaria. Previous research has shown that bats harbor several dangerous viruses, including SARS, Ebola, Nipah, Hendra, Marburg, and MERS, as well as various bacterial, fungal, and protozoan pathogens. Despite these findings, information about the composition of the bat blood microbiome remains limited. The present study aimed to characterize the microbial diversity present in the blood of bats inhabiting caves in Bulgaria.
Materials and Methods: Blood samples were collected from bat species belonging to the families Vespertilionidae and Rhinolophidae inhabiting three caves in Bulgaria. Between 10 and 30 µL of blood was obtained from each individual. Samples from 122 bats were combined into 14 pooled samples. Additionally, heart tissue and two spleens were collected. DNA extraction was performed, followed by metagenomic sequencing using Illumina shotgun technology with a sequencing depth of 6 Gb. Taxonomic classification of quality-filtered reads was conducted using the Kraken2 tool with the RefSeq NCBI bacterial database within the Galaxy platform (www.usegalaxy.eu). Operational taxonomic unit (OTU) tables were generated using Bracken and visualized with Pavian software.
Results: Metagenomic analysis revealed the presence of numerous microbial taxa in bat blood samples. A notable abundance of potentially pathogenic bacteria was detected, with sequencing reads exceeding 10000 for species belonging to the genera Mycobacterium, Mycoplasma, and Bartonella.
Conclusions: The results indicate that bats in Bulgaria may serve as hidden or potential reservoirs of bacterial pathogens with zoonotic relevance. These findings highlight the importance of continued surveillance of bat-associated microbiota to better understand potential public health risks.