Real Time PCR and Culture-Based Virus Isolation Test in Clinically Recovered Patients: Is the Subject Still Infectious for SARS-CoV2?

• Main Authors: Viviana Manzulli, Giulia Scioscia, Giulio Giganti, Maria Rosaria Capobianchi, Donato Lacedonia, Lorenzo Pace, Dora Cipolletta, Pasquale Tondo, Rosella De Nittis, Valeria Rondinone, Luigina Serrecchia, Antonio Parisi, Domenico Galante, Sergio Lo Caputo, Teresa Antonia Santantonio, Damiana Moschetta, Vitangelo Dattoli, Antonio Fasanella, Maria Pia Foschino Barbaro
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Journal of Clinical Medicine
• Subjects: cell culture; COVID-19; RT-PCR; SARS-CoV-2; viral transmission
• Online Access: https://www.mdpi.com/2077-0383/10/2/309

Background. The highly variable manifestation of the COVID-19 disease, from completely asymptomatic to fatal, is both a clinical and a public health issue. The criteria for discharge of hospitalized patients have been based so far on the negative result of Real-Time Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) tests, but the persistence of viral fragments may exceed that of the integral virus by weeks. The aim of our study was to verify the clearance of the virus at viral culture in patients hospitalized for COVID-19 that have clinically recovered but are still positive on nasopharyngeal swab. Methods. The study was conducted in hospitalized patients with positive RT-PCR on nasopharyngeal swab. Patients included were from asymptomatic to severe cases and performed nasopharyngeal control swabbing on day 14 for asymptomatic patient or at least three days after remission of symptoms. RT-PCR positive specimens were sent to a biosafety level 3 laboratory for viral culture. Results. We performed a combined analysis of RT-PCR and a highly sensitive in vitro culture from 84 samples of hospitalized patients. The average age was 46 ± 20.29, and 40.5% of the subjects had radiologically confirmed pneumonia, with average PaO₂ of 72.35 ± 12.12and P/F ratio of 315 ± 83.15. Ct values for the N gene were lower in the first swab than in the control one (<i>p </i>< 0.001). The samples from 83 patients were negative at viral culture, and RT-PCR on the respective supernatants always confirmed the absence of viral growth. Conclusions. Our preliminary results demonstrate that patients clinically recovered for at least three days show the viral clearance at viral culture, and presumably they continued to not be contagious.