Antimicrobial Activity Of Chitosan On Mastitics- Causing Pathogens

Abstract

Chitosan is a polysaccharide derived from the deacetylation of chitin. It primarily presents in the structural exoskeletons of crustaceans. With non-toxic, biocompatible and biodegradable properties, antimicrobial and fungal activity, chitosan has been researched as one of the most potential candidates for an alternative source of antibiotics in dairy farming. This study is a preliminary experiment to investigate the antibacterial activity of chitosan extracted from shrimp shells in the laboratory. The main purpose of this study is to screen and evaluate the antibacterial activity of five different chitosan samples against four pathogens (Streptococcus agalactiae, Streptococcus uberis, Staphylococcus epidermidis and Pseudomonas sp.) causing bovine mastitis. This work was carried out by agar well diffusion and MIC broth micro dilution. Regarding agar well diffusion, it was performed to test the inhibitory action of 1% (m/V) of each chitosan sample dissolved in 1% of acetic acid against above mentioned pathogens after 24 hours inoculated. Sample 1, sample 2 and sample 3 had unclear the diameter of inhibition zones at 1% concentration, meanwhile, sample 4 and 5 expressed the effective inhibition against most pathogens at the same concentration. In terms of MIC assay, the MIC values of acetic acid for those pathogens at 0.125%. Furthermore, the result of MIC assay for five chitosan samples dissolved in 1% of acetic acid showed that chitosan combined with orange and grape essential oil (sample 5) was the best antibacterial effect against these pathogens causing mastitis compared to other samples in both methods. Particularly, it showed higher antimicrobial activity against Streptococcus sp. (S. agalactiae and S. uberis) at 19.53 mg/L than Staphylococcus sp. (S. epidermidis) at 39.06 mg/L and the least effective antimicrobial activity on Pseudomonas sp. at 78.13 mg/L. The MIC values of sample 1 and sample 2 were above 2500mg/L. The MIC value of sample 3 was determined at 78.13 mg/L against S. agalactiae and S. uberis. These MIC values were determined at below 0.125% acetic acid, so it could be guaranteed that the inhibitory action at these concentrations due to only chitosan. In conclusion, the differences in the amount of components among samples lead to the difference in the effective antimicrobial activity. Furthermore, chitosan exhibits high antibacterial activity when combined with other antimicrobial compounds.