{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T23:51:00Z","timestamp":1782777060536,"version":"3.54.5"},"reference-count":42,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2024,6,3]],"date-time":"2024-06-03T00:00:00Z","timestamp":1717372800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Italian Ministry of Health (Programme CCM 2020 Ricerca Corrente\u2014Linea 1 on emerging and re-emerging infections)","award":["871029"],"award-info":[{"award-number":["871029"]}]},{"name":"European Virus Archive\u2014GLOBAL","award":["871029"],"award-info":[{"award-number":["871029"]}]},{"name":"Valentino s.p.a. (6.2.5 Sviluppo e validazione di test diagnostici)","award":["871029"],"award-info":[{"award-number":["871029"]}]},{"name":"National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d, IRCCS","award":["871029"],"award-info":[{"award-number":["871029"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>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 \u00b5M 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 \u00b1 0.6 Log copies\/mL). Furthermore, six samples were stratified based on the Ct values of SARS-CoV-2 RNA (Ct &lt; 20, 20 &lt; Ct &lt; 30, Ct &gt; 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.<\/jats:p>","DOI":"10.3390\/ijms25116156","type":"journal-article","created":{"date-parts":[[2024,6,3]],"date-time":"2024-06-03T10:06:01Z","timestamp":1717409161000},"page":"6156","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Rapid Determination of SARS-CoV-2 Integrity and Infectivity by Using Propidium Monoazide Coupled with Digital Droplet PCR"],"prefix":"10.3390","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0955-2074","authenticated-orcid":false,"given":"Giuseppe","family":"Sberna","sequence":"first","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cosmina","family":"Mija","sequence":"additional","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eleonora","family":"Lalle","sequence":"additional","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gabriella","family":"Rozera","sequence":"additional","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2948-4243","authenticated-orcid":false,"given":"Giulia","family":"Matusali","sequence":"additional","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1952-5117","authenticated-orcid":false,"given":"Fabrizio","family":"Carletti","sequence":"additional","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8182-5896","authenticated-orcid":false,"given":"Enrico","family":"Girardi","sequence":"additional","affiliation":[{"name":"Scientific Direction, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7489-5271","authenticated-orcid":false,"given":"Fabrizio","family":"Maggi","sequence":"additional","affiliation":[{"name":"Laboratory of Virology and Biosafety Laboratories, National Institute for Infectious Diseases \u201cLazzaro Spallanzani\u201d (IRCCS), 00149 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,6,3]]},"reference":[{"key":"ref_1","unstructured":"(2024, May 03). 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