Affiliation:
1. Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases “Lazzaro Spallanzani” (IRCCS), 00149 Rome, Italy
2. Scientific Direction, National Institute for Infectious Diseases “Lazzaro Spallanzani” (IRCCS), 00149 Rome, Italy
Abstract
SARS-CoV-2 is a highly infectious virus responsible for the COVID-19 pandemic. Therefore, it is important to assess the risk of SARS-CoV-2 infection, especially in persistently positive patients. Rapid discrimination between infectious and non-infectious viruses aids in determining whether prevention, control, and treatment measures are necessary. For this purpose, a method was developed and utilized involving a pre-treatment with 50 µM of propidium monoazide (PMAxx, a DNA intercalant) combined with a digital droplet PCR (ddPCR). The ddPCR method was performed on 40 nasopharyngeal swabs (NPSs) both before and after treatment with PMAxx, revealing a reduction in the viral load at a mean of 0.9 Log copies/mL (SD ± 0.6 Log copies/mL). Furthermore, six samples were stratified based on the Ct values of SARS-CoV-2 RNA (Ct < 20, 20 < Ct < 30, Ct > 30) and analyzed to compare the results obtained via a ddPCR with viral isolation and a negative-chain PCR. Of the five samples found positive via a ddPCR after the PMAxx treatment, two of the samples showed the highest post-treatment SARS-CoV-2 loads. The virus was isolated in vitro from both samples and the negative strand chains were detected. In three NPS samples, SARS CoV-2 was present post-treatment at a low level; it was not isolated in vitro, and, when detected, the strand was negative. Our results indicate that the established method is useful for determining whether the SARS-CoV-2 within positive NPS samples is intact and capable of causing infection.
Funder
Ministero della Salute
European Virus Archive – GLOBAL
Reference42 articles.
1. (2024, May 03). World Health Organization. Available online: https://www.who.int/emergencies/diseases/novel-coronavirus-2019.
2. Persistent SARS-CoV-2 PCR Positivity Despite Anti-Viral Treatment in Immunodeficient Patients;Chan;J. Clin. Immunol.,2023
3. Clinical and epidemiological factors causing longer SARS-CoV-2 viral shedding: The results from the CoviCamp cohort;Grimaldi;Infection,2024
4. Danzetta, M.L., Amato, L., Cito, F., Di Giuseppe, A., Morelli, D., Savini, G., Mercante, M.T., Lorusso, A., Portanti, O., and Puglia, I. (2020). SARS-CoV-2 RNA Persistence in Naso-Pharyngeal Swabs. Microorganisms, 8.
5. What are the Clinical Implications of a Positive RT-PCR Test 6 Months after a Mild SARS-CoV-2 Infection?;Hvozdara;Eur. J. Case Rep. Intern. Med.,2021