Effectiveness of Different Molecular Weights and Concentrations of Chitosan on Enteric Viral Surrogates

Chitosan is known to be antibacterial and antifungal, but information on its effectiveness against foodborne viruses is limited. Enteric viruses are a major concern in food safety, especially human noroviruses which are the leading cause of nonbacterial gastroenteritis. The overall goal of this research was to determine the antiviral effectiveness of chitosan. The specific objectives were to determine the effects of molecular weight (MW) and concentration of chitosan against the cultivable enteric viral surrogates, feline calicivirus (FCV-F9), murine norovirus (MNV-1), and bacteriophages (MS2 and phiX174). Purified chitosans (53, 222, 307, 421, ~1,150kDa) were dissolved in water, 1% acetic acid, or aqueous HCl (pH= 4.3), and sterilized by membrane filtration. The solutions were mixed with equal volume of virus suspension to obtain a virus titer of 5 log PFU/ml and chitosan concentration of 0.7% for all five MW and 0.7, 1.0, 1.25, and 1.5% for 53 and 222kDa. The samples were incubated for 3 hr at 37°C before viral enumeration. Controls included untreated viruses in PBS, in PBS with acetic acid, and in PBS with HCl. Chitosan showed the greatest reduction of MS2, followed by FCV-F9, phi X174, and MNV-1. A MW effect was seen with MS2, with higher MW being more efficient, and 0.7% of ~1,150kDa causing complete inactivation. Increasing the concentration of chitosan from 0.7 to 1.5% reduced the titer of MS2 and FCV-F9 by 5.16 and 2.91 logs, respectively. Although chitosan was ineffective against MNV-1, its ability to significantly reduce MS2 and FCV-F9, suggest its use for future foodborne viral control.