Mouth Washing Impaired SARS-CoV-2 Detection in Saliva

Monique Melo Costa (1) , Nicolas Benoit (2) , Hervé Tissot-Dupont (3) , Matthieu Million (3) , Bruno Pradines (1) , Samuel Granjeaud (4) , Lionel Almeras (1)

1 VITROME - Vecteurs - Infections tropicales et méditerranéennes
2 IRBA - Institut de Recherche Biomédicale des Armées [Antenne Marseille]
3 MEPHI - Microbes évolution phylogénie et infections
4 CRCM - Centre de Recherche en Cancérologie de Marseille

Background: A previous study demonstrated the performance of the Salivette® (SARSTEDT, Numbrecht, Germany) as a homogeneous saliva collection system to diagnose COVID-19 by RT-qPCR, notably for symptomatic and asymptomatic patients. However, for convalescent patients, the corroboration of molecular detection of SARS-CoV-2 in paired nasopharyngeal swabs (NPS) and saliva samples was unsatisfactory. Objectives: The aim of the present work was to assess the concordance level of SARS-CoV-2 detection between paired sampling of NPSs and saliva collected with Salivette® at two time points, with ten days of interval. Results: A total of 319 paired samples from 145 outpatients (OP) and 51 healthcare workers (HW) were collected. Unfortunately, at day ten, 73 individuals were lost to follow-up, explaining some kinetic missing data. Due to significant waiting rates at hospitals, most of the patients ate and/or drank while waiting for their turn. Consequently, mouth washing was systematically proposed prior to saliva collection. None of the HW were diagnosed as SARS-CoV-2 positive using NPS or saliva specimens at both time points (n = 95) by RT-qPCR. The virus was detected in 56.3% (n = 126/224) of the NPS samples from OP, but solely 26.8% (n = 60/224) of the paired saliva specimens. The detection of the internal cellular control, the human RNase P, in more than 98% of the saliva samples, underlined that the low sensitivity of saliva specimens (45.2%) for SARS-CoV-2 detection was not attributed to an improper saliva sample storing or RNA extraction. Conclusions: This work revealed that mouth washing decreased viral load of buccal cavity conducting to impairment of SARS-CoV-2 detection. Viral loads in saliva neo-produced appeared insufficient for molecular detection of SARS-CoV-2. At the time when saliva tests could be a rapid, simple and non-invasive strategy to assess large scale schoolchildren in France, the determination of the performance of saliva collection becomes imperative to standardize procedures.

Mots clés: saliva; COVID-19 diagnosis; coronavirus; SARS-CoV-2

Domaines: Bactériologie; Cardiologie et système cardiovasculaire; Maladies émergentes; Maladies infectieuses; Parasitologie; Virologie

Monique Melo Costa, Nicolas Benoit, Hervé Tissot-Dupont, Matthieu Million, Bruno Pradines, et al.. Mouth Washing Impaired SARS-CoV-2 Detection in Saliva. Diagnostics, 2021, 11 (8), pp.1509. ⟨10.3390/diagnostics11081509⟩. ⟨hal-03429107⟩