{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,14]],"date-time":"2026-05-14T18:59:02Z","timestamp":1778785142394,"version":"3.51.4"},"reference-count":33,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2023,1,27]],"date-time":"2023-01-27T00:00:00Z","timestamp":1674777600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand","award":["R016435049"],"award-info":[{"award-number":["R016435049"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>During the COVID-19 pandemic, the parasitology laboratories dealing with fecal samples for the diagnosis of gastrointestinal parasitic infections are confronting the unsaved virus-containing samples. To allow for safe downstream processing of the fecal samples, a protocol for preparing a fecal smear is urgently needed. Formalin was tested with or without isotonic forms for virus inactivation using porcine epidemic diarrhea virus (PEDV) as a representative, as it belongs to the Coronaviridae family. The results revealed complete inactivation activity of 10% formalin and 10% isotonic formalin on coronavirus after 5 min of treatment at room temperature. Both also inhibited Naegleria fowleri growth after 5 min of treatment at 37 \u00b0C without disruption of the structure. In addition to these key findings, it was also found that isotonic formalin could stabilize both red and white blood cells when used as a solution to prepare fecal smears comparable to the standard method, highlighting its value for use instead of 0.9% normal saline solution for the quantification of blood cells without active virus. The 10% isotonic formalin is useful to safely prepare a fecal smear for the diagnosis of parasites and other infections of the gastrointestinal tract during the COVID-19 pandemic.<\/jats:p>","DOI":"10.3390\/diagnostics13030466","type":"journal-article","created":{"date-parts":[[2023,1,30]],"date-time":"2023-01-30T08:28:23Z","timestamp":1675067303000},"page":"466","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Formalin Inactivation of Virus for Safe Downstream Processing of Routine Stool Parasite Examination during the COVID-19 Pandemic"],"prefix":"10.3390","volume":"13","author":[{"given":"Pisith","family":"Chinabut","sequence":"first","affiliation":[{"name":"Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nuntiya","family":"Sawangkla","sequence":"additional","affiliation":[{"name":"Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Suphaluck","family":"Wattano","sequence":"additional","affiliation":[{"name":"Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8094-3273","authenticated-orcid":false,"given":"Techit","family":"Thavorasak","sequence":"additional","affiliation":[{"name":"Center of Research Excellence in Therapeutic Proteins and Antibody Engineering, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Weluga","family":"Bootsongkorn","sequence":"additional","affiliation":[{"name":"Siriraj Integrative Center for Neglected Parasitic Diseases, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anchalee","family":"Tungtrongchitr","sequence":"additional","affiliation":[{"name":"Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3732-4637","authenticated-orcid":false,"given":"Pichet","family":"Ruenchit","sequence":"additional","affiliation":[{"name":"Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"},{"name":"Siriraj Integrative Center for Neglected Parasitic Diseases, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,27]]},"reference":[{"key":"ref_1","unstructured":"(2021, June 01). Timeline-COVID-19. Available online: https:\/\/www.who.int\/news\/item\/29-06-2020-covidtimeline\/."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Lin, F., Zhang, H., Li, L., Yang, Y., Zou, X., Chen, J., and Tang, X. (2022). PEDV: Insights and advances into types, function, structure, and receptor recognition. Viruses, 14.","DOI":"10.3390\/v14081744"},{"key":"ref_3","unstructured":"(2022, December 14). COVID Live-Coronavirus Statistics\u2013Worldometer. Available online: https:\/\/www.worldometers.info\/coronavirus\/."},{"key":"ref_4","unstructured":"(2022, December 14). Coronavirus Disease (COVID-19): How Is It Transmitted?. Available online: https:\/\/www.who.int\/news-room\/questions-and-answers\/item\/coronavirus-disease-covid-19-how-is-it-transmitted\/."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1061","DOI":"10.1001\/jama.2020.1585","article-title":"Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus\u2013infected pneumonia in Wuhan, China","volume":"323","author":"Wang","year":"2020","journal-title":"JAMA"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"991","DOI":"10.1080\/22221751.2020.1760144","article-title":"Isolation of infectious SARS-CoV-2 from urine of a COVID-19 patient","volume":"9","author":"Sun","year":"2020","journal-title":"Emerg. Microbes Infect."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"a006031","DOI":"10.1101\/mcs.a006031","article-title":"The gut microbiome: A missing link in understanding the gastrointestinal manifestations of COVID-19?","volume":"7","author":"Brooks","year":"2021","journal-title":"Mol. Case Stud."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"469","DOI":"10.1080\/22221751.2020.1732837","article-title":"Detectable 2019-NCoV viral RNA in blood is a strong indicator for the further clinical severity","volume":"9","author":"Chen","year":"2020","journal-title":"Emerg. Microbes Infect."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"264","DOI":"10.1016\/j.ijid.2020.02.050","article-title":"Comparison of different samples for 2019 novel coronavirus detection by nucleic acid amplification Tests","volume":"93","author":"Xie","year":"2020","journal-title":"Int. J. Infect. Dis."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1920","DOI":"10.3201\/eid2608.200681","article-title":"Infectious SARS-CoV-2 in feces of patient with severe COVID-19","volume":"26","author":"Xiao","year":"2020","journal-title":"Emerg. Infect. Dis."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1518","DOI":"10.1053\/j.gastro.2020.02.054","article-title":"COVID-19: Gastrointestinal manifestations and potential fecal-oral transmission","volume":"158","author":"Gu","year":"2020","journal-title":"Gastroenterology"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.medj.2022.04.001","article-title":"Gastrointestinal symptoms and fecal shedding of SARS-CoV-2 RNA suggest prolonged gastrointestinal infection","volume":"3","author":"Natarajan","year":"2022","journal-title":"Med"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"502","DOI":"10.1038\/s41591-020-0817-4","article-title":"Characteristics of pediatric SARS-CoV-2 infection and potential evidence for persistent fecal viral shedding","volume":"26","author":"Xu","year":"2020","journal-title":"Nat. Med."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Ruenchit, P. (2021). State-of-the-Art techniques for diagnosis of medical parasites and arthropods. Diagnostics, 11.","DOI":"10.3390\/diagnostics11091545"},{"key":"ref_15","unstructured":"Joshua, E.B., Bradley, D., and Sandeep, S. (2022). Physiology, Body Fluids, StatPearls Publishing."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"4598","DOI":"10.1021\/acs.jproteome.1c00320","article-title":"Inactivation of Coronaviruses during sample preparation for proteomics experiments","volume":"20","author":"Grossegesse","year":"2021","journal-title":"J. Proteome Res."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Xiao, S., Yuan, Z., and Huang, Y. (2022). Disinfectants against SARS-CoV-2: A review. Viruses, 14.","DOI":"10.3390\/v14081721"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1089\/bio.2013.0010","article-title":"Inactivation of influenza A virus, Adenovirus, and Cytomegalovirus with PAXgene tissue fixative and formalin","volume":"11","author":"Kap","year":"2013","journal-title":"Biopreservation Biobank."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"43","DOI":"10.2166\/wst.1985.0094","article-title":"Inactivation of Hepatitis A virus by heat and formaldehyde","volume":"17","author":"Flehmig","year":"1985","journal-title":"Water Sci. Technol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"13928","DOI":"10.1128\/JVI.02694-14","article-title":"Effect of formaldehyde inactivation on Poliovirus","volume":"88","author":"Wilton","year":"2014","journal-title":"J. Virol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"6235","DOI":"10.1074\/jbc.M310752200","article-title":"Identification of formaldehyde-induced modifications in proteins: Reactions with model peptides","volume":"279","author":"Metz","year":"2004","journal-title":"J. Biol. Chem."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Thavorasak, T., Chulanetra, M., Glab-Ampai, K., Teeranitayatarn, K., Songserm, T., Yodsheewan, R., Sae-Lim, N., Lekcharoensuk, P., Sookrung, N., and Chaicumpa, W. (2022). Novel neutralizing epitope of PEDV S1 protein identified by IgM monoclonal antibody. Viruses, 14.","DOI":"10.3390\/v14010125"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"780","DOI":"10.1016\/S1995-7645(13)60138-8","article-title":"Comparison of direct fecal smear microscopy, culture, and polymerase chain reaction for the detection of Blastocystis sp. in human stool samples","volume":"6","author":"Santos","year":"2013","journal-title":"Asian Pac. J. Trop. Med."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"81","DOI":"10.54846\/jshap\/348","article-title":"Diagnostic notes update on porcine epidemic diarrhea","volume":"10","author":"Pospischil","year":"2002","journal-title":"J. Swine Health Prod."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1462","DOI":"10.1093\/infdis\/jiaa507","article-title":"Methods of inactivation of SARS-CoV-2 for downstream biological assays","volume":"222","author":"Patterson","year":"2020","journal-title":"J. Infect. Dis."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Rodr\u00edguez-Enr\u00edquez, A., Herrera-Camacho, I., Mill\u00e1n-P\u00e9rez-Pe\u00f1a, L., Reyes-Leyva, J., Santos-L\u00f3pez, G., Rivera-Ben\u00edtez, J.F., and Rosas-Murrieta, N.H. (2022). Predicted 3D model of the M protein of Porcine Epidemic Diarrhea Virus and analysis of its immunogenic potential. PLoS ONE, 17.","DOI":"10.1371\/journal.pone.0263582"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Ruenchit, P., Whangviboonkij, N., Sawasdipokin, H., Phumisantiphong, U., and Chaicumpa, W. (2021). A Search for anti-Naegleria fowleri agents based on competitive exclusion behavior of microorganisms in natural aquatic environments. Pathogens, 10.","DOI":"10.3390\/pathogens10020142"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1089\/ten.tec.2021.0060","article-title":"Cell viability sssays in three-dimensional hydrogels: A comparative study of accuracy","volume":"27","author":"Dominijanni","year":"2021","journal-title":"Tissue Eng. Part C Methods"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1292\/jvms1939.37.229","article-title":"Disinfectant effects of several chemicals against Toxoplasma oocysts","volume":"37","author":"Ito","year":"1975","journal-title":"Nihon Juigaku Zasshi Jpn. J. Vet. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1590\/S0036-46652010000200006","article-title":"Subcutaneous immunization against Leishmania major-infection in mice: Efficacy of formalin-killed promastigotes combined with adjuvants","volume":"52","author":"Mutiso","year":"2010","journal-title":"Rev. Inst. Med. Trop. S\u00e3o Paulo"},{"key":"ref_31","first-page":"317","article-title":"The effects of some factors on the growth and morphology of Naegleria sp. and three strains of the Genus Acanthamoeba","volume":"22","author":"Kadlec","year":"1975","journal-title":"Folia Parasitol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"400","DOI":"10.4103\/0973-029X.102496","article-title":"Chemical and physical basics of routine formaldehyde fixation","volume":"16","author":"Thavarajah","year":"2012","journal-title":"J. Oral Maxillofac. Pathol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1002\/ca.20567","article-title":"Evaluation of methods to reduce formaldehyde level of cadavers in the dissection laboratory","volume":"21","author":"Whitehead","year":"2008","journal-title":"Clin. Anat."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/13\/3\/466\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:17:12Z","timestamp":1760120232000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/13\/3\/466"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,1,27]]},"references-count":33,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2023,2]]}},"alternative-id":["diagnostics13030466"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics13030466","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,1,27]]}}}