Gut bacteria isolates of Hirudinaria manillensisand its antibacterial activities

Leeches have been used in traditional and modern medical practices for centuries; however, information on leech species identification, gut-associated bacterial communities, and their potential antimicrobial interactions remains limited. This study aimed to identify leech specimens and isolate and characterise their gut-associated microbiota with potential antibacterial activity. Leech samples were collected from two locations: Kemaman, Terengganu, and Jengka, Pahang, Malaysia. Species identification was conducted based on external and internal morphological characteristics. Gut bacteria were isolated and differentiated according to colony morphology and cellular characteristics. The antibacterial activity of the isolates was evaluated using cross-streaking and disk diffusion assays against selected pathogenic bacteria, namely Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Morphological analysis confirmed that all leech specimens belonged to the dark buffalo leech, Hirudinaria manillensis. A total of three bacterial isolates were successfully obtained from the leech gut, of which two showed observable zones of inhibition against the tested bacteria. Overall, this study provides baseline information on the morphology of H. manillensis and its associated gut microbiota. The findings enhance current understanding of leech–microbe interactions and provide a basis for future studies on the antimicrobial potential of leech-associated bacteria.