Novel Probiotic Mechanisms of the Oral Bacterium Streptococcus sp. A12 as Explored with Functional Genomics.

Health-associated biofilms in the oral cavity are composed of a diverse group of microbial species that can foster an environment that is less favorable for the outgrowth of dental caries pathogens, like Streptococcus mutans A novel oral bacterium, designated Streptococcus A12, was previously isolated from supragingival dental plaque of a caries-free individual and was shown to interfere potently with the growth and virulence properties of S. mutans In this study, we applied functional genomics to begin to identify molecular mechanisms used by A12 to antagonize, and to resist the antagonistic factors of, S. mutans Using bioinformatics, genes that could encode factors that enhance the ability of A12 to compete with S. mutans were identified. Selected genes, designated potential competitive factors (pcf), were deleted. Certain mutant derivatives showed a reduced capacity to compete with S. mutans compared to that of the parental strain. The A12 pcfO mutant lost the ability to inhibit comX -inducing peptide (XIP) signaling by S. mutans, while mutants with changes in the pcfFEG locus were impaired in sensing of, and were more sensitive to, the lantibiotic nisin. Loss of PcfV, annotated as a colicin V biosynthetic protein, resulted in diminished antagonism of S. mutans Collectively, the data provide new insights into the complexities and variety of factors that affect biofilm ecology and virulence. Continued exploration of the genomic and physiological factors that distinguish commensals from truly beneficial members of the oral microbiota will lead to a better understanding of the microbiome and new approaches to promote oral health.IMPORTANCE Advances in defining the composition of health-associated biofilms have highlighted the important role of beneficial species in maintaining health. Comparatively little, however, has been done to address the genomic and physiological bases underlying the probiotic mechanisms of beneficial commensals. In this study, we explored the ability of a novel oral bacterial isolate, Streptococcus A12, to compete with the dental pathogen Streptococcus mutans using various gene products with diverse functions. A12 displayed enhanced competitiveness by (i) disrupting intercellular communication pathways of S. mutans, (ii) sensing and resisting antimicrobial peptides, and (iii) producing factors involved in the production of a putative antimicrobial compound. Research on the probiotic mechanisms employed by Streptococcus A12 is providing essential insights into how beneficial bacteria may help maintain oral health, which will aid in the development of biomarkers and therapeutics that can improve the practice of clinical dentistry.

The relationship between bowel cancer and fiber content in the diet.

Colon cancer, very rare in rural South African blacks, is also rare in urban dwellers despite considerable rise in prosperity. The disease has scarcely increased during the last quarter of a century. The same situation applies to appendicitis. Endeavors to characterize different black populations in transition (including subjects who have had appendicitis) are being made respecting 1) diet, especially dietary fiber intake; 2) bowel physiology (e.g., transit time); 3) concentrations of fecal bile acids and other metabolites; and 4) the activity of certain fecal enzymes.

Colon cancer and diet, with special reference to intakes of fat and fiber.

Colon cancer, rare in the past, and in developing populations, currently accounts for 2 to 4% of all deaths in Western populations. Evidence suggests the primary cause to be changes in diet, which affect the bowel milieu intérieur. It is possible that in sophisticated populations, the higher concentrations of fecal bile acids and sterols, and longer transit time, favor the production of potentially carcinogenic metabolites. Of secular changes in diet, evidence suggests that the following may have etiological importance: 1) the fall in intake of fiber-containing foods with its effects on bowel physiology, and 2) the decreased fiber but increased fat intakes, in their respective capacities to raise concentrations of fecal bile acids, sterols, and other noxious substances. For possible prophylaxis against colon cancer, recommendations for a lower fat intake, or a higher intake of fiber-containing foods (apart from fiber ingestion from bran) are extremely unlikely to be adopted. For future research, western populations with considerably lower than average mortality rates, e.g., Seventh Day Adventists, Mormons, the rural Finnish population, as well as developing populations, demand intensive study. Also requiring elucidation are the respective roles of diet and of genetic constitution on concentrations of fecal bile acids, etc., and on transit time, in prone and nonprone populations.

Pattern of cancer in Indian patients hospitalized in Durban, South Africa.

In emigrants from less to more developed countries, consequent changes in environmental factors are associated, inter alia, with changes in occurrences of the chronic diseases of lifestyle. In South Africa, most immigrants from India arrived in the early 1900s. To learn of the current pattern of cancer in the descendants of these people, enquiries were made on several series of patients admitted to RK Khan Hospital in Durban. The results were then compared with those of patients admitted to Ambojogai Hospital, North West India, the ancestral home of the majority of South African Indians. The most prominent differences were the lower percentages in South African Indians in respect of cancers of the mouth/pharynx in both sexes and of cervical cancer, and their considerably higher percentages, principally in the cases of stomach cancer in both sexes, of prostate cancer in males and of breast cancer in females. Discussion of risk factors indicates that in such populations there could be some control over the rises in some cancers, and on reductions in others. However, endeavours at prevention are hindered not only by the lack of knowledge prevailing, but also by their general indifference; likewise, this is the case with western populations.

In vivo enamel fluoride uptake from and caries inhibition by topical fluoride agents.

Acidulated phosphate fluoride (APF), Duraphat or Fluor Protector, was applied to the molar teeth of rats fed a cariogenic diet. The first maxillary molar teeth were subjected to a microbiopsy procedure for fluoride analysis and the mandibular molars scored for caries. All three topical fluoride agents produced a significant increase in the fluoride content of the outermost 5.0 micron of enamel. Only APF produced a significant reduction in caries incidence at all sites.

In vitro fluoride uptake, distribution and retention by human enamel after 1- and 24-hour application of various topical fluoride agents.

The in vitro fluoride acquisition by human enamel after a 1-hour and 24-hour application of APF, Duraphat (a resin varnish) or Fluor Protector (a polyurethane varnish) and subjection to various procedures was determined. Fluoride acquisition was the greatest in teeth treated with Fluor Protector and the least in APF-treated teeth. Fluoride uptake and distribution were increased by prolonging the contact time between the varnishes and enamel, and fluoride retention was decreased after subsequent exposure to synthetic saliva.

Effects of transition on bowel diseases in sub-Saharan Africans.

In populations in sub-Saharan Africa, transitional changes in patterns of morbidity and mortality are taking place, with decreases in the diseases of poverty and infection, but rises in chronic diseases of prosperity, associated, however, with greater longevity. Remarkably, bowel diseases - appendicitis, diverticular disease, colon cancer - while nearly absent in rural areas, have very low incidences in urban dwellers, despite rises in risk factors, including a decreasing intake of fibre-containing foods. Currently, there is no explanation for the phenomenon, which stands in marked contrast to the considerable rises which have occurred in dental caries, obesity in women and diabetes.

Salivary glands and saliva of Amblyomma variegatum ticks: comparison of immatures and adults in relation to the pathogenesis of dermatophilosis.

Salivary glands from immature and adult Amblyomma variegatum were compared for differences in potential components responsible for the systemic aggravation by adult ticks of the skin disease dermatophilosis. Whole salivary glands from adult, nymphal and larval A. variegatum ticks were compared for structural differences by light microscopy and for protein content by gel electrophoresis. Type-2 salivary gland acini from adult ticks at the second stage of feeding contained significantly greater (P < 0.01) proportions of c1 secretory granules than those from either of the immature instars. There was also significantly more area occupied with e secretory granules in the type-3 salivary gland acini from adult ticks compared with larval ticks. Electrophoresis of whole salivary glands showed seven bands present only in the adult material; of these, three were dense bands at 37, 35 and 31 kDA. Electrophoresis of saliva from adult and nymphal A. variegatum obtained by artificial stimulation showed that nine bands were unique to the saliva produced by adults; of these nine bands one was a dense band at 67 kDa. It was concluded that adult salivary material was different from that of immature ticks and that further studies on the relationship between the feeding of adult A. variegatum and dermatophilosis should investigate these components unique to the adults.

Patterns of tooth vulnerability to caries in South African high school pupils.

Caries prevalence and distributions were studied in 761 South African high school pupils aged 17 years in four ethnic groups, living in urban (low F) and rural (low and high F) areas. Mean DMFT values were significantly higher among White pupils than all other groups. Comparison of mean DMFT among the Black pupils showed that urban Black dwellers had a significantly higher score than rural pupils when caries-free individuals were included in the analysis, but not when scores for only those with a DMFT of 1 or more were compared. No significant differences were found between the DMFT values of Black rural pupils living in high or low fluoride areas. Among Black rural pupils, dental caries was approximately three times more common in permanent second molars compared with permanent first molars. In urbanized Black, Coloured, Indian and White subjects, the molars were approximately equally affected.

Contrasting patterns of caries profile and dental treatment in pupils of 16-18 years in South African ethnic groups.

Investigations on caries profile and state of teeth treatment were made on 3752 high school pupils of 16-18 years, namely, rural and urban Black, Indian, Colored (Eur-African-Malay) and White pupils. Rural Blacks had a low mean DMFT of about 2, and a caries-free prevalence of 52%. Of the few with affected teeth, 10% were extracted, none filled, and 90% decayed; i.e. restorative dental attention was virtually nil. Among English and Afrikaans pupils attending Government Schools, mean DMFT was about 10, and caries-free prevalence negligible. Of affected teeth, 13% were extracted, 59% filled and 28% decayed. The situations regarding the urban Black, Indian and Colored groups were intermediate. The Jewish pupils, well-circumstanced and attending private school, had a mean DMFT of 6.5, moreover 6% were caries-free. Of affected teeth, 1% had been extracted; 93% were filled, and only 6% remained decayed. Since it transpired that the diets of the three White subgroups, cariogenically, were much the same, the advantageous position of the Jewish pupils was judged to be due primarily to their excellent oral hygiene motivation, particularly their demonstrably regular visits to dentists.

Dental caries in South African black and white high school pupils in relation to sugar intake and snack habits.

DMFT scores, total sugar intakes and snacks habits were determined in 1918 South African Black pupils (923 rural, 995 urban) and 724 White pupils (English and Afrikaans speaking) aged 16-18 years inclusive. Mean DMFT scores of school groups of Black pupils (both sexes) ranged from 0.9 and 2.0 in rural areas, to 4.2-6.7 in urban areas (where data were far higher than such obtained 7 years ago), and were 9.2 and 10.2 for White pupils. Corresponding mean daily sugar intake were - rural Blacks, 69 g and 97 g, urban Blacks 118-141 g, respectively (all slightly higher than previously); and Whites 102 g and 123 g. Mean DMFT scores of girls were higher than those of boys; yet while mean sugar intakes of Blacks girls and boys were somewhat similar, White girls' intakes were much lower than those of White boys. In the ethnic-sex groups studied, mean DMFT scores for pupils in upper, compared with lower, third of sugar intake, were higher in nine of the 14 sub-groups. Mean DMFT scores in upper, compared with lower, third of exposure to snack practices were higher in 11 of the 14 groups. However, most of the differences were slight. In further research, more intensive enquiries should be pursued on roles of ethnic and familial factors, as well as on roles of inter-acting dietary components additional to sugar and sugar-containing foods.

Dental caries and blood groups in South African blacks.

DMFT scores were determined in series of 1) urban Black adolescents (132 boys, 143 girls) aged 16-18 yr, and 2) rural Black mothers (480) aged 20-35 yr. Each series was divided into upper and lower thirds, with respect to DMFT. No relationship was apparent between segments with good versus inferior teeth, and blood groups.

Sugar consumption and dental caries: evidence from 90 countries.

An examination is made of data on dental caries amongst 12-year-old children and sugar consumption of the total population for 90 countries. For the whole data set, DMFT score tends to rise with sugar consumption. The linear relationship between the logarithm of DMFT and sugar is estimated to have a slope of 0.021 per kg/year per head of population (P < 0.0001), and accounts for 28% of the variation in DMFT. In contrast, when data from 29 industrialised nations are analysed separately, there is no evidence of a sugar-caries relationship; the slope of the linear regression line is estimated to be -0.013, not significantly different from zero. This latter result is in agreement with the considerable evidence of a lack of strong relationship between the amount of sugar consumed and caries occurrence in Western countries. These results suggest that, in addition to sugar, other factors, such as other aspects of diet, exposure to fluoride and genetic effects, must be taken into account when seeking to explain variations in caries prevalence, and when making recommendations for caries control.

Perplexing features in the occurrence of dental caries and its relationship to sugar intake.

Epidemiologically, there are numerous perplexing features, insufficiently appreciated, in the occurrences of degenerative diseases, and in the roles of their risk factors. This applies particularly to dental caries, the commonest of all diseases, and the risk factor, sugar intake. In some contexts, caries scores are much lower, or are much higher, than expected. Moreover, even in contexts where outwardly the same risk factors are widespread, ranges of scores are much wider than would be expected. In all contexts, among groups and more especially among individuals, the association of caries experience and dietary intakes, particularly that of sugar intake, is limited. Accordingly, caution must be exercised in the over-blaming of sugar and in the overclaiming of benefits to be derived from reducing intake.