IN VITRO ANTIBACTERIAL ACTIVITY OF CHITOSAN NANOPARTICLES AGAINST Vibro parahaemolyticus AND V. alginolyticus

In the economically important shrimp industry, vibrios have become a major constraint on production. They are widely responsible for several diseases and mortality in shrimp farming. Members of the genus Vibrio such as V. harveyi, V. parahaemolyticus, V. alginolyticus etc. are usually associated with shrimp diseases. Use of antibiotics to control the incidence of diseases may lead to antibiotic resistance in aquaculture. In search of effective and environmentally friendly bactericidal material to improve the health of the shrimp, chitosan could be an option as it has shown potent antimicrobial activity against several pathogenic bacteria. Chitosan is a bioactive derivative of chitin; chitosan nanoparticles are found to have increased antibacterial activity compared to chitosan. In this present study, antibacterial activity of chitosan nanoparticles (ChNPs) against V. parahaemolyticus and V. alginolyticus was studied.

Different concentrations (1, 2, 3, 5, 10 mg/ml) of Chitosan solutions were prepared in 25mM sodium acetate and mixed well using magnetic stirrer for 4-5 hours. ChNPs formed were filter sterilized through 0.2µm filter and characterised using Zetasizer ver.7.12. The mean size of 1, 2, 3, 5, 10 mg/ml ChNPs was found to be 108.7, 116.4, 191.5, 192.3, 334.nm respectively (Fig. 1).

Muller-Hinton agar was prepared and culture of V. parahaemolyticus and V. alginolyticus were seeded over it and ChNPs of different concentrations (1, 2, 3, 5, 10 mg/ml) impregnated on sterile paper disc was placed on it. After 24 hours of incubation at 32±1°C, antibacterial activity as the diameter (mm) of the clear inhibitory zone formed around the discs was recorded (Table 1).