Abstract

Background: Chitosan (deacetylated chitin) and its derivatives, which are known to possess pharmaceutical and biomedical properties, have gained considerable attention in the biomedical field. The nontoxic, biocompatible, and biodegradable nature of chitosan makes it possible to use it for therapeutic purpose. It exhibits antibacterial effect on both Gram-positive and Gram-negative cell wall types of bacteria and so-called “antimicrobial polysaccharide.”

Aims and Objective: To study the antibacterial activities of native chitosan and its derivatives against three Gram-negative bacteria (Escherichia coli, Klebsiella spp., and Proteus spp.).

Materials and Methods: Bactericidal activity of native chitosan, chitosan hydrolysates obtained by hydrogen peroxide (H2O2) and lysozyme degradation, chitosan–zinc (Zn) complex, and glucosamine hydrochloride was tested against ATCC strains of E. coli, Klebsiella spp., and Proteus spp. and clinical isolates of E. coli, Klebsiella spp., and Proteus spp. procured from a clinical diagnostic laboratory. Statistical analysis was done using SPSS software, version 20.

Results: Both chitosan and its derivatives markedly inhibited the growth of most bacteria tested; however, the effects differed with regard to the type of the bacterium. The minimum inhibitory concentration for E. coli ATCC strain was 50 µg and its bactericidal activity was dose dependent. Chitosan hydrolysates also exhibited an inhibitory effect, although differences were seen among strains. Degrades from H2O2 had higher activity than native chitosan. Lysozyme-degraded chitosan had less activity compared to hydrolysates obtained from H2O2 hydrolysis. Chitosan–Zn complex also showed wide spectrum of antimicrobial activities against all the microorganisms tested and the effects were found to increase with increasing chelate ratios. No antibacterial effect was observed in the case of monomer glucosamine hydrochloride, showing that only oligomers have bactericidal effect.

Conclusion: The antibacterial potential of chitosan and its derivatives is considerable and its prospect to be developed as a chemotherapeutic agent is high.

Key words: Chitosan; Chitosan Derivatives; Chitosan–Zn Complex; Glucosamine Hydrochloride; Antibacterial Activity; E. coli; Klebsiella spp.; Proteus spp.