Phenotypic and genotypic characterization of Thai oral streptococci, lactobacilli and pediococci

This work was to assess the isolation and identification of Thai oral bacteria. Seventeen viridans group streptococci (VGS) and seventeen lactic acid bacteria from saliva were characterization based on their morphological, physiological and biochemical characteristics and the 16S RNA gene sequences analysis. The Gram-positive cocci in chains of viridans group comprised of six isolates (Group I) were identified as Streptococcus gordonii, 6 isolates (Group II) were Streptococcus salivarius, 4 isolates (Group III) were Streptococcus sanguis and one isolate (Group IV) was Streptococcus mutans. Seventeen lactic acid bacterial isolates were Gram-positive and catalase negative. They did not contained diaminopimelic acid in the cell wall peptidoglycan. They were divided into four groups, the rod-shaped in Group A (11 isolates) and Group B (2 isolates) which were identified as Lactobacillus fermentum and Lactobacillus salivarius, respectively. The tetrad-forming cocci in Group C (3 isolates) and Group D (1 isolate) were identified as Pediococcus acidilactici and P. pentosaceus, respectively.

Degradation of serine-containing oligopeptides by Peptostreptococcus micros ATCC 33270

BACKGROUND/AIMS

Microorganisms of Peptostreptococcus micros are asaccharolytic, anaerobic gram-positive cocci that are frequently isolated from human oral sites such as periodontal pockets. Preliminary study showed that several amino acids, including serine, enhanced slightly the growth of P. micros. Therefore, we investigated the degradation of serine and serine-containing oligopeptides.

METHODS

Metabolic end products were determined with high-performance liquid chromatography. The related enzymatic activities in cell-free extract were also assayed.

RESULTS

Washed P. micros degraded serine-tripeptides (Ser-Ser-Ser), and produced formate, pyruvate, acetate, and ammonia. They also degraded serinyl-tyrosine (Ser-Tyr) to the same products. Related enzymatic activities, such as serine dehydratase, pyruvate formate-lyase, formate dehydrogenase, pyruvate oxidoreductase, phosphate acetyltransferase, and acetate kinase, were detected in the cell-free extract, indicating that the organisms produced ATP in the serine metabolism.

CONCLUSION

P. micros utilized serine-containing oligopeptides as exogenous metabolic substrates rather than serine itself, and degraded Ser-Ser-Ser and Ser-Tyr to formate, pyruvate, acetate, and ammonia with ATP generation.

Mutans streptococci in a Thai population: relation to caries and changes in prevalence after application of fissure sealants

The aims of this study were to evaluate the level of mutans streptococci in two groups of Thai (Bangkok) children; to relate the findings to caries prevalence and to the caries increment over 2 years, and to study whether different sealant and fluoride programmes affected levels of mutans streptococci over a 2-year period. The baseline survey comprised 1,114 children aged 12 years. For the sealant project, a minimum of three caries-free permanent molars was required; 752 children aged 12-13 and 512 children aged 7-8 years were distributed into five groups: control group, Delton fissure sealant group, glass ionomer fissure sealant applied by dentist (GIC-dentist group) or by school teachers given a 3-day course (GIC-teacher group), and an HF group (0.5% HF solution applied 3 times). The WHO standard criteria were used to record caries. Prevalence of mutans streptococci was estimated using the Strip mutans test. Mean DMFT (n = 1,114) of 12-years-olds was 2.96; 17% had Strip mutans class 0 (low level), 32% class 1, 33% class 2 and 18% class 3 (the corresponding mean DFT +/- SD for each mutans streptococci class was 1.84 +/- 2.33, 2.23 +/- 2.14, 3.18 +/- 2.75, and 3.59 +/- 3.01 respectively). For the 7- to 8-year-olds (n = 512), mean df teeth at baseline was 5.36 (d = 5.19; f = 0.17); 5% had Strip mutans class 0, 17% class 1, 33% class 2 and 45% class 3 (the corresponding mean df teeth was 3.19 +/- 2.5, 4.13 +/- 2.84, 4.89 +/- 2.94 and 6.39 +/- 3.16 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)