Extended biofilm formation time by Streptococcus sanguinis modifies its non-cariogenic behavior, in vitro

Abstract Although the commensal Streptococcus sanguinis [ S. sanguinis] is isolated from caries-free people, it can ferment carbohydrates producing acids. We aimed to characterize S. sanguinis cariogenic potential as a function of different enamel biofilm formation periods, in vitro. Saliva-coated enamel slabs were inoculated with S. sanguinis to form initial biofilms for 8, 12 or 16 h in presence of sucrose and followed by a period in medium with glucose for 16, 12 or 8 h, respectively, until completion of 24 h. To simulate cariogenic challenges, S. sanguinis biofilms were exposed to 10% sucrose for 5 minutes, 3x/day for 5 days. Biofilm biomass, viable cells, total proteins, intracellular and extracellular polysaccharides production, acidogenicity and enamel demineralization were determined. Biofilms of Streptococcus mutans [ S. mutans ] served as caries-positive control. Biofilms of S. sanguinis forming on enamel for 12 and 16 h showed higher demineralization than those formed during 8 h, but lower than S. mutans biofilms, regardless of the initial biofilm formation time. No differences were detected in the biofilm properties among the different biofilm formation times tested for S. sanguinis . Increased enamel initial biofilm formation time by S. sanguinis appears to induce a cariogenic potential, but lower than S. mutans .

Prevalence of oral lesions and chronic non-communicable diseases in a sample of chilean institutionalized versus non-institutionalized elderly

Chile is experiencing a process of demographic aging with an increase in the number of elderly people, a percentage of which resides in long-term establishments for the elderly (LEE). however, there is little information on the reality of the elderly in these long-term care facilities, so this study was conducted to compare the epidemiological profile of the prevalent oral pathologies as well as chronic non-communicable diseases (NCDs), of institutionalized versus non-institutionalized elderly subjects. seventy-six institutionalized and forty-three non-institutionalized subjects were examined intraorally, and their clinical health record, gender and age were obtained, according to inclusion/exclusion criteria. the results indicate that female gender is the most common, with an average age of 78.5 year, with those 80 years old and above comprising the predominant group. the most prevalent oral lesions within the institutionalized group were denture stomatitis and irritative hyperplasia, while in the non-institutionalized these two lesions were found less frequently. as for the presence of xerostomia, there was no difference between the groups. the most common condition in both groups was total maxillary and mandibular edentulous, with the latter variable present more frequently in the institutionalized group (p<0.05). the predominant NCD for both groups were arterial hypertension, arthritis-osteoarthritis and diabetes mellitus (p>0.05), and depression was the most prevalent NCD in the non-institutionalized group (p<0.05). this study provides valuable information on the epidemiology of elderly´s oral lesions and NCDs to inform the decision-making process of public health policies.

Genomic organization of the structural genes controlling the astaxanthin biosynthesis pathway of Xanthophyllomyces dendrorhous

The cloning and nucleotide sequence of the genes (idi, crtE, crtYB, crtl and crtS) controlling the astaxanthin biosynthesis pathway of the wild-type ATCC 24230 strain of Xanthophyllomyces dendrorhous in their genomic and cDNA version were obtained. The idi, crtE, crtYB, crtl and crtS genes were cloned, as fragments of 10.9, 11.5, 15.8, 5.9 and 4 kb respectively. The nucleotide sequence data analysis indicates that the idi, crtE, crtYB, crtl and crtS genes have 4, 8,4, 11, and 17 introns and 5, 9, 5, 12 and 18 exons respectively. In addition, a highly efficient site-directed mutagenesis system was developed by transformation by integration, followed by mitotic recombination (the double recombinant method). Heterozygote idi (idi+ / idi-::hph), crtE (crtE+ / crtE -::hph), crtYB (crtYB + / crtYB -::hph), crtI (crtI+ / crtI-::hph) and crtS (crtS +/crtS -::hph) and homozygote mutants crtYB (crtYB -::hph/crtYB -::hph), crtI (crtI -::hph/crtI -::hph) and crtS (crtS -::hph / crtS -::hph) were constructed. All the heterozygote mutants have a pale phenotype and produce less carotenoids than the wild-type strain. The genetic analysis of the crtYB, crtl and crtS loci in the wild-type, heterozygote, and homozygote give evidence of the diploid constitution of ATCC 24230 strains. In addition, the cloning of a truncated form of the crtYB that lacks 153 amino acids of the N-terminal region derived from alternatively spliced mRNA was obtained. Their heterologous expression in Escherichia coli carrying the carotenogenic cluster of Erwinia uredovora result in trans-complementation and give evidence of its functionality in this bacterium, maintaining its phytoene synthase activity but not the lycopene cyclase activity.