Investigating the Antibacterial Properties of Leech Saliva: Starvation and Dose-Dependent Effect of Crude Leech Saliva Extraction (CLSE) on Bacterial Strains

Abstract

The Asian buffalo leech, Hirudinaria manillensis, emerges as a prominent species utilized for medicinal purposes due to its physiological similarities to the European medicinal leech. Hirudotherapy is renowned for its diverse mechanisms of action, including the anticoagulant properties of hirudin found in leech saliva, which inhibit thrombin and prevent blood clotting. This study investigates the impact of feeding 60 leeches on their weight gain and protein concentration in their saliva over an 8-week starvation period, and the antibacterial efficacy of crude leech saliva extraction (CLSE) against E. coli, Klebsiella sp., and Salmonella sp. To the starved leech, the weight gain was highest in the 2nd week (55.06%), 38.82% in the 4th week and followed by a 50.68% increase in the 8th week. The protein concentrations, measured using the Bradford assay, were highest in the 4th week starvation and declined thereafter.  The CLSE concentrations tested at 25%, 50%, 75%, and 100% showed increased inhibition zones for all bacterial strains, with Klebsiella sp. demonstrating the highest sensitivity on the 4^th week starved leeches. On the 4^th week starvation, the Salmonella sp. strains exhibited inhibition zones ranging from 15 mm to 35 mm, while Klebsiella sp. strains ranged from 25 mm to 45 mm. E. coli strains showed a less pronounced response. The positive control (Chloramphenicol) showed a 35 mm inhibition zone. These findings indicate that CLSE has a starvation time and dose-dependent antibacterial effect, particularly against Klebsiella sp. Further research is recommended to understand the factors affecting protein concentration in leech saliva and to optimize CLSE’s antibacterial properties.