The role of Staphylococcus aureus quorum sensing in cutaneous and systemic infections.

BACKGROUND: Staphylococcus aureus is a leading cause of human bacterial infections worldwide. It is the most common causative agent of skin and soft tissue infections, and can also cause various other infections, including pneumonia, osteomyelitis, as well as life-threatening infections, such as sepsis and infective endocarditis. The pathogen can also asymptomatically colonize human skin, nasal cavity, and the intestine. S. aureus colonizes approximately 20-30% of human nostrils, being an opportunistic pathogen for subsequent infection. Its strong ability to silently spread via human contact makes it difficult to eradicate S. aureus. A major concern with S. aureus is its capacity to develop antibiotic resistance and adapt to diverse environmental conditions. The variability in the accessory gene regulator (Agr) region of the genome contributes to a spectrum of phenotypes within the bacterial population, enhancing the likelihood of survival in different environments. Agr functions as a central quorum sensing (QS) system in S. aureus, allowing bacteria to adjust gene expression in response to population density. Depending on Agr expression, S. aureus secretes various toxins, contributing to virulence in infectious diseases. Paradoxically, expressing Agr may be disadvantageous in certain situations, such as in hospitals, causing S. aureus to generate Agr mutants responsible for infections in healthcare settings. MAIN BODY: This review aims to demonstrate the molecular mechanisms governing the diverse phenotypes of S. aureus, ranging from a harmless colonizer to an organism capable of infecting various human organs. Emphasis will be placed on QS and its role in orchestrating S. aureus behavior across different contexts. SHORT CONCLUSION: The pathophysiology of S. aureus infection is substantially influenced by phenotypic changes resulting from factors beyond Agr. Future studies are expected to give the comprehensive understanding of S. aureus overall profile in various settings.

Pathogenic role of the staphylococcal accessory gene regulator quorum sensing system in atopic dermatitis.

The skin is home to various bacteria, archaea, fungi, and viruses, collectively referred to as the skin microbiota. Patients with certain skin diseases reportedly have unique skin "dysbiosis," a condition involving imbalanced microbiota, suggesting that dysbiosis in the skin may be either causal or a consequence of specific skin diseases. Atopic dermatitis (AD) is the most common allergic skin disease that affects 15-20% of children and 2-10% of adults worldwide. Both intrinsic genetic factors, such as susceptibility to type 2 inflammation or skin barrier dysfunction, and extrinsic environmental factors, such as air pollen and skin microbiota, contribute to AD. Staphylococcus aureus, which does not often colonize the skin of healthy individuals, is commonly identified in the lesional skin of patients with AD and is correlated with the disease flare. However, the role of S. aureus in the pathogenesis of AD has not been elucidated. Here, we discuss the pathological behavior of S. aureus, focusing on accessory gene regulator (Agr) quorum sensing, which is a fundamental bacterial cell-to-cell interaction mechanism that affects the behavior of S. aureus and other members of the microbial community. Importantly, beyond bacteria-bacteria interactions, the Agr quorum sensing system also regulates various virulence factors, which induce type 2 and IL-17-dependent skin inflammation in the host. Furthermore, the colonization of Agr-positive S. aureus in early life accelerates the development of pediatric AD. Finally, we aim to highlight the current efforts to establish novel therapeutic methods to ameliorate or prevent AD through Agr-targeted intervention.

Utility of biphasic calcium phosphate cement as a seal for root-end filling.

The recently developed biphasic calcium phosphate cement (BCPC) consists of α-tricalcium phosphate-tetracalcium phosphate as the solid phase and calcium phosphate solution as the liquid phase. BCPC powder is composed of a single solid solution with a monomodal size distribution. Here, we used a bacterial leakage model to examine the utility of BCPC as a seal for root-end filling. We prepared large (median particle size=9.96 µm; BCPC-L) and small (median particle size=4.84 µm; BCPC-S) BCPC powders. In total, 45 single-rooted teeth were instrumented, resected at the root-end, and retrofilled with experimental materials. Mineral trioxide aggregate (MTA) was used as the control. After visual confirmation of BCPC powder size and retrofilling quality by microscopy, bacterial leakage tests were conducted using Enterococcus faecalis. The bacterial leakage tests did not reveal any significant differences between BCPC-S and MTA. Our findings suggest that BCPC-S is useful for root-end filling.

Relation between number of teeth, malnutrition, and 3-year mortality in elderly individuals ≥85 years.

OBJECTIVE: The number of teeth has been shown to affect mortality. However, it is unclear why the number of teeth is associated with mortality. We focused on the number of teeth and malnutrition and examined whether these differences affect 3-year all-cause mortality among very elderly individuals. METHODS: This analysis was conducted using data from the Tokyo Oldest Old Survey on Total Health study. Altogether 513 participants ≥85 years were categorized based on remaining teeth (0, 1-7, 8-18, ≥19). All-cause mortality was determined by calculating the cumulative 3-year survival rate according to the remaining number of teeth and the presence/absence of malnutrition. Further, hazard ratios (HRs) were analyzed using Cox regression analyses. RESULTS: No difference was observed according to the number of teeth (p = 0.638), but the presence/absence of malnutrition was significantly associated with mortality (p < 0.001). Malnutrition was independently associated with higher HRs, even after adjusting for confounding factors associated with mortality. (HR: 2.315, 95% CI: 1.431-3.746). Additionally, adjusting for the number of teeth, HR remained significant (HR: 2.365, 95% CI: 1.449-3.853). CONCLUSION: In the very elderly, malnutrition-but not the number of teeth-was independently associated with 3-year all-cause mortality after adjusting for various health issues.

Effectiveness of Acid-electrolyzed Functional Water for Mouth Wash: An In Vitro Study.

BACKGROUND/AIM: Acid-electrolyzed functional water (FW) is an efficient bactericide and gargling with FW might be an effective method of oral care. We investigated the possible use of FW as a mouth wash by an in vitro study. MATERIALS AND METHODS: The bactericidal effect of FW against different species of bacteria (Staphylococcus aureus, Streptococcus pneumonia, Pseudomonas aeruginosa, and Candida albicans) was evaluated using the numbers of colony-forming units (CFU). The experiment was conducted using PBS, LISTERINE, and ConCool F (undiluted, and the optimal concentration indicated). To investigate the bactericidal mechanism of FW, the activity of superoxide dismutase (SOD), an indicator of oxidative action, was measured in S. aureus. FW was diluted with purified water to concentrations of 10, 30, 50, and 70%. The numbers of CFU were measured for each concentration. XTT assays were performed using HSC-3 and HeLa cells, to examine the viability of the cells following treatment with FW. The same experiment was conducted with PBS, LISTERINE, and undiluted ConCool F. RESULTS: No bacteria treated with FW formed colonies. SOD activity peaked at a 50% concentration of FW and was more than twice that of the control. A significant decrease in the number of CFU was observed following 50% treatment. Since the peaks of the SOD activity and the starting concentrations of the bactericidal effects coincided, the bactericidal effect of FW might be related to its oxidative effects. Bacteria treated with FW had the same survival rate as the other mouth washes. CONCLUSION: FW might be clinically applicable as a mouth wash.

Associations of poor oral health with frailty and physical functioning in the oldest old: results from two studies in England and Japan.

BACKGROUND: Very few studies have examined the relationship of oral health with physical functioning and frailty in the oldest old (> 85 years). We examined the association of poor oral health with markers of disability, physical function and frailty in studies of oldest old in England and Japan. METHODS: The Newcastle 85+ Study in England (n = 853) and the Tokyo Oldest Old Survey on Total Health (TOOTH; n = 542) comprise random samples of people aged > 85 years. Oral health markers included tooth loss, dryness of mouth, difficulty swallowing and difficulty eating due to dental problems. Physical functioning was based on grip strength and gait speed; disability was assessed as mobility limitations. Frailty was ascertained using the Fried frailty phenotype. Cross-sectional analyses were undertaken using logistic regression. RESULTS: In the Newcastle 85+ Study, dry mouth symptoms, difficulty swallowing, difficulty eating, and tooth loss were associated with increased risks of mobility limitations after adjustment for sex, socioeconomic position, behavioural factors and co-morbidities [odds ratios (95%CIs) were 1.76 (1.26-2.46); 2.52 (1.56-4.08); 2.89 (1.52-5.50); 2.59 (1.44-4.65) respectively]. Similar results were observed for slow gait speed. Difficulty eating was associated with weak grip strength and frailty on full adjustment. In the TOOTH Study, difficulty eating was associated with increased risks of frailty, mobility limitations and slow gait speed; and complete tooth loss was associated with increased risk of frailty. CONCLUSION: Different markers of poor oral health are independently associated with worse physical functioning and frailty in the oldest old age groups. Research to understand the underlying pathways is needed.

Association between maximum occlusal force and 3-year all-cause mortality in community-dwelling elderly people.

BACKGROUND: Among the very elderly, poor oral health reduces life expectancy. In this study, differences in the magnitude of the maximum occlusal force (MOF) in the very elderly were examined in terms of effects on all-cause mortality in a 3-year follow-up. METHODS: We evaluated 489 community-living elderly individuals aged 85 years or older. MOF was measured using an occlusal force measuring device, and participants were classified into three groups according to gender- and dental status-sensitive tertiles. Demographic variables, cognitive, physical function, psychological status, oral health, comorbidity, and blood chemistry factors were assessed. One-way analyses of variance, χ (2) tests, and the Kruskal-Wallis test were used for statistical analyses. The relationship between MOF tertiles and 3-year all-cause mortality was examined using a multivariate Cox model analysis after adjusting for confounding factors. RESULTS: MOF tertiles were significantly associated with cognitive impairment, number of teeth, limitations on chewable foods, handgrip strength, timed up-and-go test, and diabetes mellitus. During the follow-up period, 74 subjects died. Subjects with the highest MOF had a significantly lower mortality rate than other groups (log rank P  =  0.031). In the univariate Cox model, MOF tertiles were independently associated with a lower risk of death (HR = 0.69, 95 % CI = 0.51-0.91). Even after adjusting for various confounders in the multivariate Cox model (Model 1), MOF was independently associated with a lower risk of death (HR = 0.67, 95 % CI = 0.50-0.91). In model 2, we added handgrip strength as a confounder and found that the HR for MOF was attenuated (HR = 0.73, 95 % CI = 0.54-0.99), but still statistically significant. CONCLUSIONS: In a cohort of the very elderly, MOF was independently associated with all-cause mortality after adjusting for various health issues. Moreover, this independent association remained after a further adjustment for handgrip strength; however, the HR was attenuated. This suggests that MOF and handgrip strength may share a common mechanism of a general decrease in muscle strength, possibly sarcopenia, which is a significant cause of mortality in the very old.