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Review 1: "Differential effects of antiseptic mouth rinses on SARS-CoV-2 infectivity in vitro"

This potentially informative in-vitro study finds that some commercially available mouth-rinses have different anti-viral activity/cytotoxicity. Additional animal models and clinical trials are needed to generalize the study’s findings.

Published onJan 30, 2021
Review 1: "Differential effects of antiseptic mouth rinses on SARS-CoV-2 infectivity in vitro"
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key-enterThis Pub is a Review of
Differential effects of antiseptic mouth rinses on SARS-CoV-2 infectivity in vitro

AbstractSARS-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.

RR:C19 Evidence Scale rating by reviewer:

  • Reliable. The main study claims are generally justified by its methods and data. The results and conclusions are likely to be similar to the hypothetical ideal study. There are some minor caveats or limitations, but they would/do not change the major claims of the study. The study provides sufficient strength of evidence on its own that its main claims should be considered actionable, with some room for future revision.



The authors present an in vitro study comparing 4 reagents contained in mouthwashes and they tested their antiviral activity against SARS-CoV-2.

The introduction correctly poses the problem. It would be interesting to have more explanations on the choice of products compared. Indeed, the authors have chosen 2 commercial products (Listerine, Colgate Peroxyl) and 2 products without commercial label (chlorhexidine gluconate, povidone iodine). Please note what we don’t know if you evaluate reagents, mouthwashes, or other. Moreover, it is not so much the generic name of the product that interests us but rather the active product that is evaluated.

It would also be necessary, in the "Materials and Methods" section, to present the composition and concentration of the different active reagents as well as the associated reagents (alcohol?) that could impact the results or create interactions.

There is confusion in the structuring of your chapters. Information produced in the Introduction has its place in the "Materials and Methods" or "Discussion" sections. Example: Line 99-106; 110-123. You must respect the guidelines.

Begin the introduction with "Antiseptic mouth rinses have been shown to have efficacy in reducing bacteria and in the oral cavity and in dental aerosols (Fine et al. 1993; Fine et al. 1996; Koletsi et al. 2020). The antiseptic Listerine and chlorhexidine gluconate-0.12% (CHG) have been shown to reduce herpes simplex virus-1 load in saliva after rinsing (Meiller et al. 2005; Park and Park 1989)" with references from 1993, 1996, 1989 and 2005, considerably undermines the scientific interest of your work. If your topic was not so topical, one might doubt the current scope of your work.

The references are too old and should be updated. 5 references are more than 15 years old out of the 14 selected. As such, it would have been logical in the discussion to address in detail the mechanisms of action of active ingredients on viruses.

References in the form of a “www” link are to be avoided in the introduction. At the very least, they should be put in the "References" section.)

You should take in considerations the 2020 publications:,, …

In the abstract, it is important to explain that our study is an in vitro study.

Line 55. Replace by: “Our results indicate that, in vitro, mouth rinses can significantly reduce virus infectivity, suggesting a potential benefit for reducing SARS-CoV-2 spread.”

Line 56. Introduce the phrasing “a potential in vitro benefit”

Note that in a "Discussion" section there is no reference to a figure or table that was included in the "Results" section.

In conclusion, this submission requires major revisions. It must be continued, because the “in vitro research” has been, scientifically, correctly carried out and the results in the context of this topical public health issue merit dissemination.

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