Purpose: The intent of this study was to determine the antimicrobial properties of chitosan, using a new fast dissolving high molecular weight chitosan, against Escherichia coli O157:H7 (Ec), Salmonella Typhimurium (ST), Vibrio cholera (Vc) and Vibrio vulnificus (Vv).
Methods: Our patent pending high molecular weight, water-soluble chitosan, with molecular weights of 789 kDa and 1017 kD, were dissolved in acetic acid (AC) at 1% w/v or aspartic acid (AS) at 1-4% w/v. Chitosan samples (1 ml) were added to 8 ml of Mueller Hinton broth, then inoculated with 1 ml of 12 h old bacteria cultures to give an initial inoculation of >6.50 log CFU/g. All samples were incubated at 25°C and bacterial counts were determined at 0, 48, and 96 h, by plating onto Mueller Hinton agar. Plates were incubated for 48 h at 37°C and Log CFU/ml determined.
Results: Chitosan treatments 789AC1%, 789AS1%, and 1017AC1% reduced Vc and Vv counts to non-detectable levels after 48 h at 25°C. Ec bacterial counts were reduced by 2 Log CFU/ml when treated with 789AC1%, 1017AC1%, 789AS2%, and 789AS4%. Only one chitosan treatment significantly reduced ST by 2 Log CFU/ml (789AC1%) from control levels.
Significance: Our results found chitosan 789AC1% was the most effective antimicrobial treatment significantly reducing Ec, ST, Vc, and Vv bacterial counts from the control levels.