Reducing Indigenous Oral Health Inequalities: A Review from 5 Nations

Indigenous populations around the world experience a disproportionate burden in terms of oral diseases and conditions. These inequalities are likely due to a complex web of social determinants that includes poverty, historical consequences of colonialism, social exclusion, government policies of assimilation, cultural annihilation, and racism in all its forms (societal, institutional). Despite documented oral health disparities, prevention interventions have been scarce in Indigenous communities. This review describes oral health interventions and their outcomes conducted for Indigenous populations of the United States, Canada, Brazil, Australia, and New Zealand. The review includes research published since 2006 that are available in English in electronic databases, including MEDLINE. A total of 13 studies were included from the United States, Canada, Brazil, and Australia. The studies reviewed provide a wide range of initiatives, including interventions for prevention and treatment of dental disease, as well as interventions that improve oral health knowledge, behaviors, and other psychosocial factors. Overall, 6 studies resulted in improved oral health in the study participants, including improvements in periodontal health, caries reduction, and oral health literacy. Preferred intervention methodologies included community-based research approaches, culturally tailored strategies, and use of community workers to deliver the initiative. Although these studies were conducted with discrete Indigenous populations, investigators reported similar challenges in research implementation. Recommendations for future work in reducing oral health disparities include addressing social determinants of health in various Indigenous populations, training future generations of dental providers in cultural competency, and making Indigenous communities true partners in research.

Evaluation of colonisation resistance in stool of human donors using ex vivo, in vitro and in vivo assays

The indigenous microbiota is the population of microorganisms normally present on the surface and mucosa of an individual, where it performs essential health functions, including the colonisation resistance (CR) against pathogens. To identify the bacteria responsible and the mechanisms involved in the CR, the germ-free (GF) animal model has been used, because in vitro studies cannot always be extrapolated to what occurs in vivo. In this study, ex vivo antagonism assays against seven enteropathogenic bacteria using stools from 15 healthy human donors confirmed that the CR showed individual variation. Using in vitro antagonism assays, 14 strains isolated from dominant faecal microbiota of donors with elevated CR were selected for mono-association in GF mice to test the in vivo antagonism against Salmonella enterica ser. Typhimurium. Mice mono-associated with Enterococcus hirae strain 8.2, Bacteroides thetaiotaomicron strain 16.2 and Lactobacillus ruminis strain 18.1 had significant reductions in faecal counts of the pathogen during the challenge. After five days of infection, the group associated with E. hirae 8.2 showed a reduction in the translocation of S. Typhimurium to the spleen, while the group associated with L. ruminis 18.1 presented an increased translocation to the liver. The histological data confirmed these results and revealed that the mice associated with E. hirae 8.2 showed fewer lesions on ileum and liver, compared to the damage caused by S. Typhimurium alone, while in mice associated with L. ruminis 18.1 there was significantly worse lesions. Concluding, from the dominant faecal microbiota from healthy human with high CR, through ex vivo, in vitro and in vivo assays, a bacterium was characterised for its high CR potential, being a candidate for probiotic use.

Weissella paramesenteroides WpK4 reduces gene expression of intestinal cytokines, and hepatic and splenic injuries in a murine model of typhoid fever

Diarrhoea in piglets by Salmonella and other pathogens can be a serious health problem. Non-drug treatments such as probiotic microorganisms have various effects on the gastrointestinal microbiota dysbiosis and host immune system modulation. The aim of this study was to demonstrate the suitable use of Weissella paramesenteroides WpK4 strain isolated from healthy piglets as an alternative prophylactic or therapeutic treatment against Salmonella Typhimurium. Out of 37 lactic acid bacteria isolates, 24 strains belonging to the Weissella and Lactobacillus genera were analysed in vitro for desirable probiotic characteristics. The W. paramesenteroides WpK4 strain fulfilled all in vitro tests: resistance to acidic pH and bile salts, hydrophobic cell surface, antagonism against bacterial pathogens, H2O2 production and exopolysaccharide secretion, and non-transferable resistance to antibiotics. Mice fed with WpK4 showed no signs of bacterial translocation to the liver or spleen and decreased Salmonella translocation to these organs. Significantly, WpK4 intake attenuated the weight loss, fostered the preservation of intestinal architecture and integrity, and promoted survival in mice following infection with Salmonella Typhimurium. In addition, WpK4 modulated immune cellular response by inhibiting the production of pro-inflammatory cytokines and inducing anti-inflammatory mediators. These findings validate the probiotic properties of W. paramesenteroides WpK4 strain, and its eventual use in piglets.

A Lactobacillus rhamnosus strain induces protection in different sites after Salmonella enterica subsp. enterica serovar Typhimurium challenge in gnotobiotic and conventional mice

The ability of a Lactobacillus rhamnosus strain isolated from a healthy breast-fed human newborn to reduce the pathological consequences for the host due to an experimental oral infection with Salmonella enterica subsp. enterica serov. Typhimurium in vivo was determined using gnotobiotic and conventional mice. Conventional mice received 0.1mL probiotic milk (8.0 log colony-forming unit) daily for 10 days before the oral pathogenic challenge (5.0 log colony-forming unit). Then probiotic treatment was continued until the end of the experiment. Probiotic treatment in germ-free mice consisted of a single dose of the probiotic milk at the beginning of the experiment and a challenge with S. Typhimurium 10 days later (3.0 log colony-forming unit). A protective effect was observed in both gnotobiotic and conventional animals in terms of histopathologic and morphometric data, but in different anatomical sites. This protection was observed in liver and intestines, respectively, for gnotobiotic and conventional mice. However, S. Typhimurium populations were similar in the feces of both treated and control gnotobiotic mice. We conclude that a protective effect of L. rhamnosus against experimental S. Typhimurium was observed. This protection was not due to the reduction of the population of pathogenic bacteria in the intestine.

[Oral health among the Xavánte Indians in Pimentel Barbosa, Mato Grosso, Brazil]

This study presents the results of an oral health epidemiological survey conducted in 1997, based on WHO criteria, in the Xavánte indigenous community of Pimentel Barbosa (or Etéñitépa), Mato Grosso State, Central Brazil. The study included 228 individuals (85% of the population) over two years of age. In about half the sample, the DMF index was less than 2, and in the 12-14-year age bracket it was 3.7. The low frequency of fillings in permanent and deciduous teeth suggests limited access to dental care services. Despite the number of sextants with bleeding and tartar, no cases of severe periodontal disease were detected (CPITN). In the community, comparison of the results of this survey with two previous surveys (1962 and 1991) showed a deterioration in oral health conditions over time and alterations in the occlusal pattern (increase in Angle class II and III). Dietary changes due to environmental and socioeconomic alterations resulting from interaction with the surrounding society, along with the lack of preventive programs, are among the causes of this deterioration in oral health among the Xavánte.