SARS-CoV2 is transmitted primarily through oral mouth secretions and respiratory droplets. Commercial mouthwashes, povidone iodine (PI), hydrogen peroxide (HP) and chlorhexidine (CHX) have been tested in cell culture and RT-PCR studies for their efficacy to reduce SARS-CoV2 burden. Here, we evaluated SARS-CoV2 burden in whole mouth fluid (WMF) and respiratory droplets (RD) samples before and after the use of PI, HP or CHX mouthwashes in hospitalized COVID-19 patients using RT-PCR and rapid antigen test (RAT). Thirty-six SARS-CoV2 RT-PCR-positive in-patients were randomly assigned to one of the four groups: 20 and 60 minutes after 1% w/v PI or 1.5% HP; 90 and 180 minutes after 1.5% HP or 0.2% w/v CHX. WMF and RD samples were collected concurrently at baseline and after the two different time points. RD (92%) showed a higher reduction in SARS-CoV2 burden than WMF samples (50%; p=0.008). SARS-CoV2 burden was statistically lower at both 20 minutes (p=0.02) and 60 minutes (p=0.03) with PI; at 20 minutes with HP (p=0.0001); and 90 minutes with CHX (p=0.04). The overall and individual mean logarithmic reductions in the WMF and RD samples were greater than 1.0 at 20, 60 and 90 minutes after PI, HP or CHX. RAT-positive patients at 90 minutes post-treatment (n=3) demonstrated a one log increase in virus copies. Among the three RAT-negative post-treatment patients, SARS-CoV2 burden declined by one log in two while the third patient had a slight increase in RNA copies. In conclusion, we have shown for the first time that the mouthwashes, PI, HP and CHX can reduce the SARS-CoV2 burden in the concurrently collected RD and WMF samples. RAT is more appropriate than RT-PCR to evaluate the efficacy of the mouthwashes.

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IntroductionSARS-CoV2, the aetiological agent of the current COVID-19 pandemic, has been detected in saliva and recently implicated in several oral diseases. Collection of nasopharyngeal swabs (NPS) and detection by reverse transcriptase-polymerase chain reaction (RT-PCR) requires medical / technical expertise. A reliable and easy to handle point-of-care (POC) test is highly desirable, especially to curb transmission. Therefore, in this study, we evaluated a commercially available POC rapid antigen test (RAT) for the detection of SARS-CoV2 antigens in the saliva of RT-PCR confirmed positive and negative patients.MethodsThirty saliva samples of 10 saliva RT-PCR negative and 20 saliva RT-PCR positive patients were tested by RAT.ResultsRAT was negative in 10/10 (100%) RT-PCR-negative samples; positive in 9/20 (45%) RT-PCR-positive samples; concordance was 63% (p=0.001). Patients with positive RAT had higher virus copies in their NPS samples compared to the RAT-negative patients. This difference was also statistically significant (p=0.01).ConclusionThus, the POC RAT may be used to detect SARS-CoV2 as a reliable tool for self-testing, large-scale population screening and emergency medical/dental screening. Patients negative by RAT should be confirmed by RT-PCR.

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