Porphyromonas gingivalis enhances pneumococcal adhesion to human alveolar epithelial cells by increasing expression of host platelet-activating factor receptor

Respiratory tract barrier dysfunction in viral-bacterial co-infection cases

A preceding viral infection of the respiratory tract predisposes the host to secondary bacterial pneumonia, known as a major cause of morbidity and mortality. However, the underlying mechanism of the viral-bacterial synergy that leads to disease progression has remained elusive, thus hampering the production of effective prophylactic and therapeutic intervention options. In addition to viral-induced airway epithelial damage, which allows dissemination of bacteria to the lower respiratory tract and increases their invasiveness, dysfunction of immune defense following a viral infection has been implicated as a factor for enhanced susceptibility to secondary bacterial infections. Given the proximity of the oral cavity to the respiratory tract, where viruses enter and replicate, it is also well-established that oral health status can significantly influence the initiation, progression, and pathology of respiratory viral infections. This review was conducted to focus on the dysfunction of the respiratory barrier, which plays a crucial role in providing physical and secretory barriers as well as immune defense in the context of viral-bacterial synergy. Greater understanding of barrier response to viral-bacterial co-infections, will ultimately lead to development of effective, broad-spectrum therapeutic approaches for prevention of enhanced susceptibility to these pathogens.

Effect of poor oral health status at hospital admission on in-hospital outcomes of older patients with aspiration pneumonia

PURPOSE

To investigate the effects of oral health status at admission on in-hospital outcomes and how it varies during hospitalization in older patients with aspiration pneumonia.

METHODS

This prospective cohort study involved patients aged ≥ 65 years who were admitted to an acute care hospital with a diagnosis of aspiration pneumonia. The patients' basic health information, length of hospital stay (LOS), and oral health assessment tool (OHAT), functional oral intake scale (FOIS), pneumonia severity index, and clinical frailty scale scores were recorded. Patients were divided into two groups based on their median OHAT scores, and intergroup changes were analyzed as a function of time. The relationship between the LOS, FOIS score upon discharge, and OHAT scores at admission was examined using multiple regression analysis.

RESULTS

Of the 89 participants (52 were men, with a mean age of 84.8 ± 7.9 years), 75 were discharged. The patients' oral health was measured weekly for 3 weeks after the initial assessment via the OHAT, wherein the median score was 7, with a significant between-group difference. Moreover, OHAT scores improved within both groups throughout their stay. OHAT scores at admission were independently associated with the LOS (B = 5.51, P = 0.009).

CONCLUSION

Poor oral health status at admission was associated with longer hospital stays. Both the high- and low-OHAT groups showed OHAT score improvements. Oral health status is critical in preventing the onset of and treating aspiration pneumonia.

Research on the Association Between Periodontitis and COPD

Periodontitis is a common chronic bacteria-initiated inflammatory disease that is closely associated with various systemic diseases, including chronic obstructive pulmonary disease (COPD). Periodontitis and COPD share similar risk factors, pathology and microorganisms. Epidemiological and clinical research have shown positive correlation between the two diseases. Individuals with severe periodontitis had a higher risk of developing COPD. Moreover, the relative risk of COPD in severe periodontitis was much higher compared to people without periodontal disease and patients with mild to moderate periodontitis. COPD patients with periodontitis had a higher frequency of COPD exacerbation and periodontal treatment demonstrated some control of COPD. However, the nature of periodontitis affecting COPD still needs further exploration. Periodontitis caused microbial and immune imbalances of the lung through several aspects: (I) under periodontitis status, periodontal pathogens directly caused the lung inflammatory reaction after inhalation and colonization on the lung, (II) periodontitis status promoted the oral colonization of pneumonia-associated pathogens, (III) periodontitis status affected the respiratory epithelium structure and (IV) periodontitis status caused imbalances in neutrophils, macrophages and inflammatory cytokines. In this review, we conclude the association between periodontitis and COPD through several aspects and further discuss the potential mechanism by which periodontitis affects COPD.

Periodontopathogens Porphyromonas gingivalis and Fusobacterium nucleatum and Their Roles in the Progression of Respiratory Diseases

The intricate interplay between oral microbiota and the human host extends beyond the confines of the oral cavity, profoundly impacting the general health status. Both periodontal diseases and respiratory diseases show high prevalence worldwide and have a marked influence on the quality of life for the patients. Accumulating studies are establishing a compelling association between periodontal diseases and respiratory diseases. Here, in this review, we specifically focus on the key periodontal pathogenic bacteria Porphyromonas gingivalis and Fusobacterium nucleatum and dissect their roles in the onset and course of respiratory diseases, mainly pneumonia, chronic obstructive pulmonary disease, lung cancer, and asthma. The mechanistic underpinnings and molecular processes on how P. gingivalis and F. nucleatum contribute to the progression of related respiratory diseases are further summarized and analyzed, including: induction of mucus hypersecretion and chronic airway inflammation; cytotoxic effects to disrupt the morphology and function of respiratory epithelial cells; synergistic pathogenic effects with respiratory pathogens like Streptococcus pneumoniae and Pseudomonas aeruginosa. By delving into the complex relationship to periodontal diseases and periodontopathogens, this review helps unearth novel insights into the etiopathogenesis of respiratory diseases and inspires the development of potential therapeutic avenues and preventive strategies.

The Association between Tannerella forsythia and the Onset of Fever in Older Nursing Home Residents: A Prospective Cohort Study

Background: Periodontal pathogens are related to the incidence of systemic diseases. This study aimed to examine whether periodontal pathogen burden is associated with the risk of fever onset in older adults. Methods: Older adults in nursing homes, aged ≥65 years, were enrolled. The study was set in Kitakyushu, Japan. The body temperatures of participants were ≥37.2 °C and were recorded for eight months. As periodontal pathogens, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia were qualified by a real-time polymerase chain reaction at the baseline. For statistical analysis, the number of bacterial counts was logarithmically conversed to 10 as a base. Results: Data from 56 participants with a median age of 88 (62−98) years were available for analysis. The logarithmic-conversed bacterial counts of T. forsythia, but not P. gingivalis or T. denticola, were associated with the onset of fever in older residents. The Kaplan−Meier method revealed that the group with <104 of T. forsythia had significantly less cumulative fever incidence than the group with ≥104 of T. forsythia. The group with ≥104 of T. forsythia was associated with an increased risk of fever onset (hazard ratio, 3.7; 98% confidence interval, 1.3−10.2; p = 0.012), which was adjusted for possible confounders. Conclusions: Bacterial burden of T. forsythia in the oral cavity was associated with the risk of the onset of fever in older nursing homes residents.

Subcutaneous abscess due to empyema necessitans caused by Porphyromonas gingivalis in a patient with periodontitis

Empyema necessitans is a rare empyema complication characterized by an extension of empyema out of the pleural space into the subcutaneous tissues of the chest wall. We herein report a case of empyema necessitans that presented as a subcutaneous chest wall abscess caused by Porphyromonas gingivalis (P. gingivalis), an important anaerobic periodontal pathogen, in a 74-year-old woman with periodontitis. The patient was admitted to our hospital with a painful soft tissue mass in the chest wall extending from a subpleural lung abscess associated with empyema. Exploratory percutaneous puncture and aspiration of the chest wall mass yielded foul-smelling chocolate-colored pus, which was found to be caused due to infection with P. gingivalis. Treatment with antibacterials resulted in a relapse of empyema necessitans requiring a second admission 1 month later. An additive treatment with surgical open drainage and decortication of the subcutaneous abscess successfully cured the abscess. Physicians must be aware of emphysema necessitans as an etiology of a chest wall mass and should consider periodontitis as a source of infection.

Porphyromonas gingivalis Components/Secretions Synergistically Enhance Pneumonia Caused by Streptococcus pneumoniae in Mice

Streptococcus pneumoniae is an important causative organism of respiratory tract infections. Although periodontal bacteria have been shown to influence respiratory infections such as aspiration pneumonia, the synergistic effect of S. pneumoniae and Porphyromonas gingivalis, a periodontopathic bacterium, on pneumococcal infections is unclear. To investigate whether P. gingivalis accelerates pneumococcal infections, we tested the effects of inoculating P. gingivalis culture supernatant (PgSup) into S. pneumoniae-infected mice. Mice were intratracheally injected with S. pneumoniae and PgSup to induce pneumonia, and lung histopathological sections and the absolute number and frequency of neutrophils and macrophages in the lung were analyzed. Proinflammatory cytokine/chemokine expression was examined by qPCR and ELISA. Inflammatory cell infiltration was observed in S. pneumoniae-infected mice and S. pnemoniae and PgSup mixed-infected mice, and mixed-infected mice showed more pronounced inflammation in lung. The ratios of monocytes/macrophages and neutrophils were not significantly different between the lungs of S. pneumoniae-infected mice and those of mixed-infected mice. PgSup synergistically increased TNF-α expression/production and IL-17 production compared with S. pneumoniae infection alone. We demonstrated that PgSup enhanced inflammation in pneumonia caused by S. pneumoniae, suggesting that virulence factors produced by P. gingivalis are involved in the exacerbation of respiratory tract infections such as aspiration pneumonia.

Relationship between the oral cavity and respiratory diseases: Aspiration of oral bacteria possibly contributes to the progression of lower airway inflammation

The global population is aging, and elderly people have a higher incidence of lower airway diseases owing to decline in swallowing function, airway ciliary motility, and overall immunity associated with aging. Furthermore, lower airway diseases in the elderly tend to have a high mortality rate. Their prevention is important for extending healthy life expectancy and improving the quality of life of each individual.

In recent years, the relationship between “chronic periodontitis and oral bacteria, especially the periodontopathic ones” and “respiratory diseases” (e.g., pneumonia, chronic obstructive pulmonary disease, and influenza) has become clear. In addition, the association of several periodontal pathogens with the onset and aggravation of coronavirus disease 2019 (COVID-19) is also being reported.

In support of these findings, oral health management has shown to reduce deaths from pneumonia and prevent influenza in nursing homes and inpatient wards. This has led to clinical and multidisciplinary cooperation between physicians and dentists, among others. However, to date, the mechanisms by which “chronic periodontitis and oral bacteria” contribute to lower airway diseases have not been well understood. Clarifying these mechanisms will lead to a theoretical basis for answering the question, “Why is oral health management effective in preventing lower airway diseases?”

JMJD3 deficiency alleviates lipopolysaccharide‑induced acute lung injury by inhibiting alveolar epithelial ferroptosis in a Nrf2‑dependent manner

Acute respiratory distress syndrome (ARDS) is a deadly illness which presents with severe hypoxemia as well as diffuse alveolar damage. Jumonji domain‑containing 3 (JMJD3), which belongs to the UTX/UTY JmjC‑domain protein subfamily, is involved in infection, development, aging and immune disorders. However, the role of JMJD3 in acute lung injury (ALI) is still unclear. The present study explored the roles and potential mechanisms of JMJD3 in ALI. Alveolar epithelial cell‑specific knockout of JMJD3 mice and A549 alveolar epithelial cells were used to investigate the function of JMJD3 in ALI. Lipopolysaccharide (LPS) was used to establish an in vivo and in vitro ALI model. The expression of JMJD3 in murine lung tissue and alveolar epithelial cells was detected. Pathological injury of lung tissue and alveolar epithelial cells was also investigated following inhibition of JMJD3. The results showed that JMJD3 expression was significantly increased in murine lung tissues and in A549 cells following LPS stimulation. JMJD3‑deficient mice in alveolar epithelial cells exhibited alleviated lung pathological injury and ferroptosis following h stimulation. Mechanistically, it was found that JMJD3 knockout could increase the expression of nuclear factor erythroid‑2‑related factor‑2 (Nrf2) in lung tissues challenged with h. However, Nrf2 overexpression by adenovirus could further enhance the anti‑ferroptotic effect from JMJD3 silence in h‑treated A549 cells. Taken together, the present study revealed that JMJD3 deficiency may relieve LPS‑induced ALI by blocking alveolar epithelial ferroptosis in a Nrf2‑dependent manner, which may serve as a novel therapeutic target against ALI.

SARS-CoV-2 Infection and Significance of Oral Health Management in the Era of "the New Normal with COVID-19"

More than a year ago, the coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was declared a pandemic by the World Health Organization, with the world approaching its fourth wave. During this period, vaccines were developed in a much shorter period than thought possible, with the initiation of the pertinent vaccination. However, oral cavities have come under renewed scrutiny worldwide because saliva, a mixture of salivary secretions, pharyngeal secretions, and gingival crevicular fluid, have not only been shown to contain infective viral loads, mediating the route of SARS-CoV-2 transmission via droplet, aerosol, or contagion, but also used as a sample for viral RNA testing with a usefulness comparable to the nasopharyngeal swab. The oral cavity is an important portal for ingress of SARS-CoV-2, being an entryway to the bronchi, alveoli, and rest of the lower respiratory tract, causing inflammation by viral infection. Moreover, angiotensin-converting enzyme 2, a host receptor for SARS-CoV-2, coupled with proteases responsible for viral entry have been found to be expressed on the tongue and other oral mucosae, suggesting that the oral cavity is the site of virus replication and propagation. Furthermore, there is a possibility that the aspiration of oral bacteria (such as periodontal pathogens) along with saliva into the lower respiratory tract may be a complicating factor for COVID-19 because chronic obstructive pulmonary disease and diabetes are known COVID-19 comorbidities with a greater risk of disease aggravation and higher death rate. These comorbidities have a strong connection to chronic periodontitis and periodontal pathogens, and an oral health management is an effective measure to prevent these comorbidities. In addition, oral bacteria, particularly periodontal pathogens, could be proinflammatory stimulants to respiratory epithelia upon its exposure to aspirated bacteria. Therefore, it may be expected that oral health management not only prevents comorbidities involved in aggravating COVID-19 but also has an effect against COVID-19 progression. This review discusses the significance of oral health management in SARS-CoV-2 infection in the era of “the new normal with COVID-19” and COVID-19 prevention with reference to the hypothetical mechanisms that the authors and the other researchers have proposed.