Differential effects of antiseptic mouth rinses on SARS-CoV-2 infectivity in vitro

Abstract

SARS-CoV-2 is detectable in saliva from asymptomatic individuals, suggesting a potential benefit from the use of mouth rinses to suppress viral load and reduce virus spread. Published studies on reduction of SARS-CoV-2-induced cytotoxic effects by antiseptics do not exclude antiseptic-associated cytotoxicity. Here, we determined the effect of commercially available mouth rinses and antiseptic povidone-iodine on the infectivity of SARS-CoV-2 virus and of a non-pathogenic, recombinant, SARS-CoV-2 infection vector (pseudotyped SARS-CoV-2 virus). We first determined the effect of mouth rinses on cell viability to ensure that antiviral activity was not a consequence of mouth rinse-induced cytotoxicity. Colgate Peroxyl (hydrogen peroxide) exhibited the most cytotoxicity, followed by povidone-iodine, chlorhexidine gluconate (CHG), and Listerine (essential oils and alcohol). Potent anti-viral activities of povidone iodine and Colgate peroxyl mouth rinses was the consequence of rinse-mediated cellular damage. The potency of CHG was greater when the product was not washed off after virus attachment, suggesting that the prolonged effect of mouth rinses on cells impacts anti-viral activity. To minimalize mouth rinse-associated cytotoxicity, mouth rinse was largely removed from treated-viruses by centrifugation prior to infection of cells. A 5% (v/v) dilution of Colgate Peroxyl or povidone-iodine completely blocked viral infectivity. A similar 5% (v/v) dilution of Listerine or CHG had a moderate suppressive effect on the virus, but a 50% (v/v) dilution of Listerine or CHG blocked viral infectivity completely. Prolonged incubation of virus with mouth rinses was not required for viral inactivation. Our results indicate that mouth rinses can significantly reduce virus infectivity, suggesting a potential benefit for reducing SARS-CoV-2 spread. ImportanceSARS-CoV-2 is detectable in saliva from asymptomatic individuals, suggesting the potential necessity for the use of mouth rinses to suppress viral load to reduce virus spread. Published studies on anti-SARS-CoV-2 activities of antiseptics determined by virus-induced cytotoxic effects cannot exclude antiseptic-associated cytotoxicity. We found that all mouth rinses tested inactivated SARS-CoV-2 viruses. Listerine and CHG were less cytotoxic than Colgate Peroxyl or povidone-iodine and were active against the virus. When mouth rinses were present in the cell culture during the infection, the potent anti-viral effect of mouth rinses were in part due to the mouth rinse-associated cytotoxicity. Our results suggest that assessing anti-viral candidates including mouth rinses with minimal potential disruption of cells may help identify active agents that can reduce SARS-CoV-2 spread.