In vitro and in vivo antibacterial activity of shrimp chitosan against some intestinal bacteria

Abstract

The effects of shrimp chitosan with deacetylation degrees (DD) of 50%, 70% and 95% (DD50, DD70, DD95) on the growth of the intestinal bacteria were investigated in vitro in the laboratory media, and in vivo by an oral feeding test using hamsters as the animal model. The antibacterial activities of these chitosan products against one strain of pathogenic Clostridium perfringens and 13 strains of probiotics, including seven strains of Lactobacillus, and six strains of Bifidobacterium were evaluated. In vitro, the antibacterial activities of DD95 and DD70 were much higher than that of DD50. The strains of probiotics were more resistant to chitosan than the pathogen of C. perfringens. The minimal lethal concentration for DD95 against C. perfringens was 250 p.p.m., whereas the survival percentages for most probiotics tested were above 90% for DD95 at 500 p.p.m. The animals were fed on either a control diet, or diets containing powdered chitosan instead of 5% cellulose in the control diet for 4 weeks. The cecal bacterial counts of total aerobes, total anaerobes, lactobacilli, bifidobacteria and clostridia were similar for the control and experimental groups. The reasons for the differences in the antibacterial activity in vitro and in vivo are discussed.