Probiotic Potential of Lactobacilli Isolated from Saliva of Periodontally Healthy Individuals.

PURPOSE: To search for useful probiotics, we characterised antimicrobial lactic acid bacteria isolated from the oral cavities of 20 healthy volunteers from Nihon Univerisity School of Dentistry. MATERIALS AND METHODS: Oral lactobacilli were isolated from the saliva of 20 periodontally healthy volunteers using the Dentocult LB dip-slide method. Primary antimicrobial screening of Lactobacillus isolates was performed using the paper disk method. Each suspected antimicrobial isolate was tested against Streptococcus mutans, S. sobrinus, and Porphyromonas gingivalis. Since P. gingivalis is considered as a keystone bacterium, we further analysed lactic acid bacteria that produced extracellular soluble antimicrobial agents that created an inhibitory zone of more than 12 mm against P. gingivalis. After two rounds of antimicrobial susceptibility testing, six isolates showing strong antibacterial effects against P. gingivalis were selected and identified as facultatively anaerobic, Gram-positive, non-spore-forming, non-capsule-forming, and catalase-negative bacilli. Selected isolates were identified to the species level through 16S rDNA sequence analyses. RESULTS: The antimicrobial substance produced by the isolated bacilli was inactivated slightly after catalase treatment, had significantly lower activity at pH levels above 9.0, and was also reduced by heat treatment above 100°C and autoclaving. The activity of the antimicrobial substance showed some resistance to lower levels of heat, as well as pepsin and proteinase K treatments. 16S rRNA sequencing identified these isolates as Lactobacillus casei, Lactobacillus fermentum, and Lactobacillus gasseri. CONCLUSION: These bacteria are antagonistic against potential periodontal pathogens and are good candidates for clinical application as probiotics.

Porphyromonas gingivalis Induces Apoptosis and Autophagy via ER Stress in Human Umbilical Vein Endothelial Cells.

It has been reported that periodontitis is associated with an increased risk of atherosclerosis. Accumulating evidence suggests that endothelial dysfunction is an early marker for atherosclerosis. To determine how periodontal infections contribute to endothelial dysfunction, we examined the effect of Porphyromonas gingivalis on human umbilical vein endothelial cells (HUVEC). P. gingivalis significantly suppressed the viability of HUVEC, induced DNA fragmentation and annexin V staining, and increased caspase-3, caspase-8, and caspase-9 activities. P. gingivalis also increased the expression of GADD153 and GRP78 and caspase-12 activity. Further, P. gingivalis induced autophagy, as evidenced by increased LC3-II and Beclin-1 levels. The suppression of P. gingivalis-induced autophagy by silencing of LC3 with siRNA significantly increased P. gingivalis-induced apoptosis. ER stress inhibitor, salubrinal, suppressed apoptosis and autophagy by inhibiting P. gingivalis-induced DNA fragmentation and LC3-II expression. These data suggest that P. gingivalis infection induces ER stress-mediated apoptosis followed by autophagic response that protects HUVEC from P. gingivalis-mediated apoptosis, potentially amplifying proatherogenic mechanisms in the perturbed vasculature.

Streptococcusdentiloxodontae sp. nov., isolated from the oral cavity of elephants.

A Gram-stain-positive, catalase-negative, coccus-shaped organism was isolated from oral cavity samples collected from healthy elephants. The isolated strain, NUM 2404T, was tentatively identified as a streptococcal species based on the results of biochemical tests. Although a comparative 16S rRNA gene sequence analysis suggested the classification of this organism into the genus Streptococcus, it did not correspond to any recognized species of the genus. Strain NUM 2404T was related most closely to Streptococcus saliviloxodontae NUM 6306T with 95.8 % 16S rRNA gene sequence similarity, but the phylogenetic tree reconstructed based on the 16S rRNA gene sequence showed that NUM 2404T clustered with Streptococcus mutans NCTC 10449T and Streptococcus troglodytae TKU 31T. Comparative sequence analysis based on two housekeeping genes, groEL, which encodes the 60 kDa heat-shock protein, and rpoB, encoding the ß subunit of RNA polymerase, of NUM 2404T indicated that it was most closely related to those of Streptococcus orisratti A63T and Streptococcus sobrinus ATCC 33478T with 82.7 and 85.1 % sequence similarities, respectively. On the basis of genotypic and phenotypic differences, it is proposed that the novel isolate be classified in the genus Streptococcus as representative of a novel species, Streptococcus dentiloxodontae sp. nov. The type strain is NUM 2404T (=JCM 19284T=DSM 27381T).

Complete Genome Sequence of Aggregatibacter actinomycetemcomitans Serotype g Strain NUM4039 (JCM 30399).

Aggregatibacter actinomycetemcomitans is considered to be a major etiological agent of aggressive periodontitis and includes serotype a to g strains. We herein report the first complete genome sequence of A. actinomycetemcomitans serotype g strain NUM4039. The genome is 2,382,853 bp in length with a G+C content of 44.34%.