Defining the oral microbiome by whole-genome sequencing and resistome analysis: the complexity of the healthy picture.

BACKGROUND: The microbiome of the oral cavity is the second-largest and diverse microbiota after the gut, harboring over 700 species of bacteria and including also fungi, viruses, and protozoa. With its diverse niches, the oral cavity is a very complex environment, where different microbes preferentially colonize different habitats. Recent data indicate that the oral microbiome has essential functions in maintaining oral and systemic health, and the emergence of 16S rRNA gene next-generation sequencing (NGS) has greatly contributed to revealing the complexity of its bacterial component. However, a detailed site-specific map of oral microorganisms (including also eukaryotes and viruses) and their relative abundance is still missing. Here, we aimed to obtain a comprehensive view of the healthy oral microbiome (HOM), including its drug-resistance features. RESULTS: The oral microbiome of twenty healthy subjects was analyzed by whole-genome sequencing (WGS) and real-time quantitative PCR microarray. Sampled oral micro-habitat included tongue dorsum, hard palate, buccal mucosa, keratinized gingiva, supragingival and subgingival plaque, and saliva with or without rinsing. Each sampled oral niche evidenced a different microbial community, including bacteria, fungi, and viruses. Alpha-diversity evidenced significant differences among the different sampled sites (p < 0.0001) but not among the enrolled subjects (p = 0.876), strengthening the notion of a recognizable HOM. Of note, oral rinse microbiome was more representative of the whole site-specific microbiomes, compared with that of saliva. Interestingly, HOM resistome included highly prevalent genes conferring resistance to macrolide, lincosamides, streptogramin, and tetracycline. CONCLUSIONS: The data obtained in 20 subjects by WGS and microarray analysis provide for the first time a comprehensive view of HOM and its resistome, contributing to a deeper understanding of the composition of oral microbiome in the healthy subject, and providing an important reference for future studies, allowing to identify microbial signatures related to functional and metabolic alterations associated with diseases, potentially useful for targeted therapies and precision medicine.

Impact of the COVID-19 pandemic on dental hygiene students in the Italian region of Emilia-Romagna.

BACKGROUND: The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a new coronavirus detected in China at the end of 2019. Because SARS-CoV-2 is highly infectious due to contamination in the air, there is a high risk of infection in the dental environment which is represents a serious problem for professionals and students (dentistry and dental hygiene). In Italy, since February 23, 2020, the government has suspended all teaching activities of schools and universities. METHODS: An anonymous questionnaire was administered to the students of the degree courses in Dental Hygiene of the Emilia Romagna Region, one of the most affected regions in Italy. The survey was intended to highlight the practical and emotional consequences of the emergency of COVID-19 on educational activities and in the training of students. RESULTS: The survey was sent to the 150 students enrolled in the universities of Bologna, Ferrara and Modena and Reggio Emilia; 141 of them completed it (94%). Since the start of the COVID-19 pandemic, several surveys have been proposed to measure the impact of this emergency situation on dental professionals; at present, however, there are still no assessments for dental hygiene degree courses, in particular aimed at assessing the psychological impact on students. CONCLUSIONS: Students consider the dental hygienist as a risky profession, while the risk taken by patients is considered as low. Given the concern reported the students, it would be useful to address the issue of proper assessment of risk during the university training of dental hygienists.

Implant-retained removable partial dentures: an 8-year retrospective study.

PURPOSE: To evaluate the long-term outcomes of removable partial dentures (RPDs) retained (but not supported) by dental implants. MATERIALS AND METHODS: We retrospectively evaluated 32 consecutive patients who received implant-retained RPDs. Each patient received one to four endosseus implants; the sample included a total of 64 implants. Follow-up was conducted for a minimum of 8 years, during which satisfaction, implant survival, and prosthetic success were evaluated. RESULTS: Patient satisfaction systematically increased. The implant success rate was 93.75%, and 100% of the prostheses were successful. CONCLUSION: Implant-retained RPDs are a reliable intermediate solution that can reduce biological and economic costs while maintaining implant treatment benefits and the ease of RPD procedures.

Oral Microbiome Dysbiosis Is Associated With Symptoms Severity and Local Immune/Inflammatory Response in COVID-19 Patients: A Cross-Sectional Study.

The human oral microbiome (HOM) is the second largest microbial community after the gut and can impact the onset and progression of several localized and systemic diseases, including those of viral origin, especially for viruses entering the body via the oropharynx. However, this important aspect has not been clarified for the new pandemic human coronavirus SARS-CoV-2, causing COVID-19 disease, despite it being one of the many respiratory viruses having the oropharynx as the primary site of replication. In particular, no data are available about the non-bacterial components of the HOM (fungi, viruses), which instead has been shown to be crucial for other diseases. Consistent with this, this study aimed to define the HOM in COVID-19 patients, to evidence any association between its profile and the clinical disease. Seventy-five oral rinse samples were analyzed by Whole Genome Sequencing (WGS) to simultaneously identify oral bacteria, fungi, and viruses. To correlate the HOM profile with local virus replication, the SARS-CoV-2 amount in the oral cavity was quantified by digital droplet PCR. Moreover, local inflammation and secretory immune response were also assessed, respectively by measuring the local release of pro-inflammatory cytokines (L-6, IL-17, TNFα, and GM-CSF) and the production of secretory immunoglobulins A (sIgA). The results showed the presence of oral dysbiosis in COVID-19 patients compared to matched controls, with significantly decreased alpha-diversity value and lower species richness in COVID-19 subjects. Notably, oral dysbiosis correlated with symptom severity (p = 0.006), and increased local inflammation (p < 0.01). In parallel, a decreased mucosal sIgA response was observed in more severely symptomatic patients (p = 0.02), suggesting that local immune response is important in the early control of virus infection and that its correct development is influenced by the HOM profile. In conclusion, the data presented here suggest that the HOM profile may be important in defining the individual susceptibility to SARS-CoV-2 infection, facilitating inflammation and virus replication, or rather, inducing a protective IgA response. Although it is not possible to determine whether the alteration in the microbial community is the cause or effect of the SARS-CoV-2 replication, these parameters may be considered as markers for personalized therapy and vaccine development.