In vivo effect of mouthwashes on viable viral load of SARS-CoV-2 in saliva: a pilot study

ABSTRACT

Current data on the efficacy of antiseptic mouthwashes to reduce viral load are contradictory. Firstly, in vitro data indicate very strong virucidal effects that are not replicated in clinical studies. Secondly, most clinical studies identify a limited effect, do not include a control/placebo group, or do not evaluate viral viability in an infection model. In the current manuscript, we perform a double-blind, randomized clinical trial where salivary viral load was measured before and after the mouthwash, and where saliva samples were also cultured in an in vitro infection model of SARS-CoV-2 to evaluate the effect of mouthwashes on viral viability. Our data show a 90–99% reduction in SARS-CoV-2 salivary copies with one of the tested mouthwashes, although we show that the remaining viruses are mostly viable. In addition, our data suggest that the active ingredient concentration and the overall excipients’ formulation can play an important role; and most importantly, they indicate that the effect is not immediate, being significant at 15 min and having maximum effectiveness after 1 h. Thus, we show that some oral mouthwashes can be useful in reducing viral transmission, although their efficacy must be improved through refined formulations or revised protocols.

KEYWORDS:

• SARS-CoV-2
• saliva
• COVID-19
• infectivity
• mouthwash
• chlorhexidine
• cymenol

Acknowledgments

We would like to thank the Microbiology Department of Fundación Jiménez Díaz University Hospital, Madrid (Spain) and Villalba General University Hospital for their work, especially Ignacio Gadea Gironés, Ricardo Fernández Roblas, Jaime Esteban Moreno, Llanos Salar Vidal, Antonio Broncano Lavado and María del Carmen Muñoz Egea; and by extension to all the members of the ENT and Cervicofacial Surgery Department of the Fundación Jiménez Díaz University Hospital, Madrid (Spain) and Villalba General University Hospital (Spain) especially Carlos Cenjor Español, Ignacio Alcalá Rueda, Gonzalo Díaz Tapia and Jessica Santillán Coello. We are also grateful for the collaboration of the FISABIO Public Health BSL-3 lab manager Luis Villamayor. The FISABIO-Public Health BSL-3 laboratory is supported by the Conselleria de Sanitat, Generalitat Valenciana and by the European Union Regional Development Fund. F. Xavier López-Labrador and Alejandro Mira are supported by the CIBERESP, Instituto de Salud Carlos III, Spain. All of our patients should receive special recognition for their acceptance to participate in our study despite their poor physical health. Our achievements are all due to them.

Disclosure statement

The current work was funded by LACER SA, which also provided the tested mouthwashes free of charge. The company played no role in the design of the clinical trial and did not participate in data analysis nor manuscript preparation. The authors declare no other potential conflicts of interest.

Author contribution

Alvaro Sánchez Barrueco contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. María Victoria MateosMoreno contributed to conception and design, contributed to analysis and interpretation, drafted and critically revised the manuscript. José Miguel Villacampa Aubá contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. Alfonso Campos González contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. Abel Bogoya Castaño contributed to design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. Raúl Rubio Yanguas contributed to design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. Asier Blanco Goñi contributed to design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. Javier Zapardiel Ferrero contributed to design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. Carlos Cenjor Español contributed to design, interpretation, drafted and critically revised the manuscript. Verónica Ausina Márquez contributed to design, data acquisition and interpretation, drafted and critically revised the manuscript. Sandra García-Esteban contributed to conception and design, contributed to interpretation, drafted and critically revised the manuscript. Alejandro Artacho contributed to design, contributed to acquisition and analysis, drafted and critically revised the manuscript. F. Xavier López Labrador contributed to design, contributed to acquisition and analysis, drafted and critically revised the manuscript. Alex Mira contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. María D. Ferrer contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript. All authors gave their final approval and agree to be accountable for all aspects of the work

Additional information

Funding

FThis work has been funded by project CPRESC00103, financed by LACER SA (Barcelona, Spain).