COVID-19, caused by the SARS-CoV-2 virus, has rapidly spread worldwide, resulting in many million infections and deaths. To date, the main method used to trace the virus is the reverse transcriptase-pcr (RT-PCR). However it has a false negative rate of 20%. So, it is necessary to identify an alternative diagnostic method. Literature data have reported gut or airway microbial characteristics in COVID-19 during hospitalisation and after recovery, but the microbiome has not been identified. The principal target of the virus, the enzyme angiotensin conversion enzyme 2 (ACE2), is expressed mainly in lung cells but also in intestinal cells. Intestinal involvement is demonstrated by the gastrointestinal symptoms that occur in about 40% of patients (diarrhea (9.6-16%), nausea and vomiting (6.6-15.3%), abdominal pain (5.7 -14.5%), but also by the presence of viral RNA in the stool of patients.
Ren and colleagues hypothesised that the oral and gut microbiome are involved in the development of COVID-19 and could serve as a new diagnostic tool. To do that, the authors sequenced 392 tongue-coating samples, 172 faecal samples and 155 serum samples from subjects in Central and East China. They characterised microbiome and lipid molecules, and verified their diagnostic potential in 74 confirmed patients from East China and 37 suspected patients. Compared with healthy controls, genera Porphyromonas and Fusobacterium, belonging to butyrate-producing bacterial families, were decreased, while five genera including Leptotrichia and Selenomonas, lipopolysaccharides-producing bacteria, were increased in confirmed patients (p<0.05). Notably, butyric acid plays an important anti-inflammatory role, and lipopolysaccharide could activate pro-inflammatory pathways so this microbial context may be involved in the inflammatory response in patients with COVID-19.
The diagnostic efficacy reached 92.11% (% (98.01% of faecal microbiome) in diagnosed suspected patients with IgG antibody positivity as confirmed patients. Compared with confirmed patients, 47 lipid molecules, including sphingomyelin and monoglyceride were depleted, and 122 lipid molecules, including phosphatidylcholine, phosphatidylethanolamine and diglyceride were enriched in recovered confirmed patients.
In this study,Ren and colleagues found that microbial alterations in SPs were consistent with CPs, suggesting a microbial model to diagnose suspected as confirmed patients on the basis of oral and gut micriobiome. Microbial markers combined with RT-PCR may further improve detection efficacy for patients with potential COVID-19 in the population, reducing both infection sources and transmission.
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