Pathogenic bacteria and fungi from bat guano in restricted access caves, Kanchanaburi Province

Abstract

Bats serve as carriers for various pathogens, with bat guano acting as a reservoir for microorganisms that can spread to the environment and cause infectious diseases in humans. This study aims to investigate the bacteria and fungi present in bat guano. Samples of bat guano were collected from restricted access cave areas and diluted using 10-fold dilutions into culture media. Initially, the researchers focused on studying fungi in bat guano, using Sabouraud Dextrose Agar supplemented with Chloramphenicol, and incubating at 37°C for 48-72 hours. Colonies were isolated, and pure cultures were obtained for analysis using MALDI-TOF MS. No fungal growth was observed at dilutions of 10^-4 to 10^-7, but growth occurred at dilutions of 10^-1, 10^-2, and 10^-3. Additionally, the variety of culture media was expanded to include Sabouraud Dextrose Agar, Potato Dextrose Agar, and Malt Extract Agar, supplemented with Chloramphenicol, and incubated at 25 and 37°C. Analysis revealed 28 isolates after selective culturing, comprising both bacteria and fungi. MALDI-TOF MS identified 9 bacterial isolates, including Providencia stuartii, Bacillus subtilis, Bacillus amyloliquefaciens, Alcaligenes faecalis, Proteus mirabilis, Ochrobactrum intermedium, Achromobacter xylosoxidans, and Stenotrophomonas maltophilia. One fungal isolate was identified as Aspergillus versicolor. Unidentified isolates underwent DNA sequencing, revealing Cladosporium perangustum. This study highlights that the majority of microorganisms present in bat guano are naturally occurring bacteria, some of which are known to cause infectious diseases in humans. These findings contribute to further research and can be used to warn individuals at risk of bat guano exposure.