The role of oral bacteria in COVID-19
Authors: Jay Patel, Victoria Sampson
Journal: The Lancet Microbe (2020)

We read with interest the Correspondence by Michael J Cox and colleagues,1Cox MJ Loman N Bogaert D O'Grady J Co-infections: potentially lethal and unexplored in COVID-19.Lancet Microbe. 2020; 1: e11Summary Full Text Full Text PDF PubMed Google Scholar highlighting the relevance of co-infections in the clinical outcomes and mortality of patients with coronavirus disease 2019 (COVID-19). We believe the role of oral bacteria in facilitating co-infections in COVID-19 is pertinent, yet overlooked. We concur with the need for whole-genome metagenomics to capture the data relevant to co-infections, but this should also warrant consideration for the bacterial species comprising the oral microbiome. Poor oral hygiene is considered to be a major ecological pressure that steers complex microbial communities in the mouth into dysbiosis. Ecological shifts in a dysbiotic ecosystem favour an increased prevalence of pathogenic oral bacteria. Daily activities such as mastication, flossing, and tooth brushing can induce bacteraemia, which facilitate haematogenous dissemination of oral bacteria and inflammatory mediators, inducing systemic inflammation in some patients. Individuals with periodontal disease show micro-ulcerated sulcular epithelia and damaged periodontal tissues, and thus seem more susceptible to bacteraemia. Good oral hygiene is therefore essential for controlling the total bacterial load in the mouth, maintaining or re-establishing the oral symbiotic equilibrium, and preventing the dissemination of oral bacteria to other sites in the body.2Kilian M Chapple I Hannig M et al.The oral microbiome – an update for oral healthcare professionals.Br Dent J. 2016; 221: 657-666Crossref PubMed Scopus (631) Google Scholar Metagenomic analyses of patients infected with severe acute respiratory syndrome coronavirus 2 have frequently reported high reads of cariogenic and periodontopathic bacteria,3Chakraborty S Metagenome of SARS-Cov2 patients in Shenzhen with travel to Wuhan shows a wide range of species - Lautropia, Cutibacterium, Haemophilus being most abundant - and Campylobacter explaining diarrhea.OSF Preprints. 2020; (published online 24 March.) (preprint).doi: 10.31219/osf.io/jegwqGoogle Scholar endorsing the notion of a connection between the oral microbiome and COVID-19 complications. Evidence suggests that periodontopathic bacteria are involved in the pathogenesis of respiratory diseases, such as those implicated in COVID-19, and are associated with chronic inflammatory systemic diseases including type 2 diabetes, hypertension, and cardiovascular disease. These diseases are frequently reported comorbidities associated with an increased risk of severe complications and death from COVID-19. Suggested mechanisms that might explain the role of oral bacteria in the pathogenesis of respiratory infections are via the aspiration of oral pathogens into respiratory organs, the alteration of the respiratory epithelium by periodontal-associated cytokines, and oral mucosal surfaces rendered to promote the adhesion of respiratory pathogens.4Scannapieco FA Role of oral bacteria in respiratory infection.J Periodontol. 1999; 70: 793-802Crossref PubMed Scopus (412) Google Scholar Numerous studies5Manger D Walshaw M Fitzgerald R et al.Evidence summary: the relationship between oral health and pulmonary disease.Br Dent J. 2017; 222: 527-533Crossref PubMed Scopus (55) Google Scholar, 6Azarpazhooh A Leake JL Systematic review of the association between respiratory diseases and oral health.J Periodontol. 2006; 77: 1465-1482Crossref PubMed Scopus (405) Google Scholar report that oral hygiene interventions in patients with pneumonia have substantially improved clinical outcomes and reduced mortality. One in ten pneumonia-related deaths of older nursing home residents (≥65 years) are considered preventable by improving oral hygiene.7Sjögren P Nilsson E Forsell M Johansson O Hoogstraate J A systematic review of the preventive effect of oral hygiene on pneumonia and respiratory tract infection in elderly people in hospitals and nursing homes: effect estimates and methodological quality of randomized controlled trials.J Am Geriatr Soc. 2008; 56: 2124-2130Crossref PubMed Scopus (255) Google Scholar Improved oral care has been shown to significantly reduce the incidence of ventilator-associated pneumonia in patients in an intensive care unit.8Mori H Hirasawa H Oda S Shiga H Matsuda K Nakamura M Oral care reduces incidence of ventilator-associated pneumonia in ICU populations.Intensive Care Med. 2006; 32: 230-236Crossref PubMed Scopus (148) Google Scholar Further metagenomic studies and clinical trials are required for the characterisation of co-infections in COVID-19 and the potential connection between the role of the oral microbiome and complications arising from the virus. These data are vital to ascertain whether poor oral hygiene is a modifiable risk factor for COVID-19 complications and if there is a place for the promotion of good oral hygiene as a preventive public health intervention during the pandemic. We declare no competing interests. We thank Dr Thuy Do (University of Leeds) for editing and providing feedback on this Correspondence. Co-infections: testing macrolides for added benefit in patients with COVID-19Co-infections and pulmonary inflammation are potentially life-threatening consequences of COVID-19. We believe that for the management of co-infections, macrolide antibiotics are particularly useful. Although azithromycin is actively being pursued,1 we would also like to suggest josamycin as a worthwhile alternative. Both macrolides are indicated for the treatment of a variety of respiratory infections including pharyngolaryngitis, acute bronchitis, and pneumonia, and the minimum inhibitory concentration of these drugs for the treatment of these infections are rapidly reached in the lungs. Full-Text PDF Open Access