Purpose: The objectives of this study were to evaluate the efficacy of hypochlorite bleach against different GI, GII, and GIV hNoV genotypes in suspension and to determine differences in susceptibility between genotypes.
Methods: The hNoV genotypes (n=11) were suspended separately in a bleach solution (50, 100, or 150 ppm) for up to five minutes followed by neutralization with fetal bovine serum. The neutralized suspension was treated with RNAse. The RNA of the intact viruses was extracted and analyzed by RT-qPCR. To determine log reduction, cycle threshold (Ct) values from untreated and treated hNoV were compared and expressed as change in Ct value.
Results: Analyses have been completed for 100 and 150ppm. Following five minutes exposure at 100 and 150ppm, GII.4 Sydney and New Orleans, GII.7, and GI.1 showed no change compared to untreated virus while a less than one-log reduction was observed for GI.5, GI.6, and GIV. Conversely, GII.3, GII.6, GII.13, and GII.16 displayed complete inactivation (three- to four-logs) at both 100 and 150 ppm after one minute exposure.
Significance: An hNoV genotype dependent efficacy of bleach inactivation is important for practical application of inactivation research. Studies using only one or a limited number of genotypes might not convey the full spectrum of hNoV susceptibility or resistance.