Inactivation of Tulane virus and feline calicivirus by aqueous ozone.

Abstract

Ongoing challenges with reproducible human norovirus cultivable assays necessitate the use of surrogates, such as feline calicivirus (FCV-F9) and Tulane virus (TV), during inactivation studies. Chlorine alternates used as control strategies include aqueous and gaseous ozone. This study aimed at determining the inactivation of FCV-F9 and TV by a portable ozone-generating device. FCV-F9 (∼8log PFU/mL) or TV (∼6log PFU/mL) in sterile-low-organic matter-containing-water was treated for 0-5min, or in sterile-water containing newborn calf serum (high-organic matter/protein) for 0-38min with ∼1ppm ozone (pH 7-6). Infectivity was determined from triplicate treatments using plaque assays. FCV-F9 titers significantly decreased by 6.07log PFU/mL after 5min in ozonated low-organic-matter-containing-water and was non-detectable (≤2log PFU/mL) after 36min treatments in high-organic-matter-containing water (p<0.05). TV titers decreased by 4.18log PFU/mL after 4min in ozonated low-organic-matter water (non-detectable after 4.5min) and were non-detectable after 22.5min treatments of high-organic-matter-containing water (p<0.05). Overall, ∼1ppm aqueous ozone significantly decreased FCV-F9 by >6logPFU/mL after 5min, TV to non-detectable levels (≤2log PFU/mL) after 4.5min and required longer treatments (>32 and >20min, respectively) for ≥4log reduction in high-organic-matter-containing water (p<0.05). For ozone treatment of both viruses, the linear and Weibull models were similar for low-organic-load water, though the Weibull model was better for the high-organic load water. Prior filtration or organic load removal is recommended before ozonation for increased viral inactivation with decreased treatment-time.