Faculty Bibliography

PURPOSE/OBJECTIVE:To evaluate the caries relapse rate for a cohort of 2- to 4-year-old children at high risk of early childhood caries when treated with an intensive fluoride varnish (FV) regimen. METHODS:Eighty paediatric patients were recruited. Forty of these patients were high risk and received the FV treatment (three applications within 2 weeks and additional applications at 1 and 3 months) during 2009-2010. Mutans streptococci (MS) levels in the saliva were evaluated during the treatment period. A comparative group of 40 children, selected from an electronic record search at the New York University College of Dentistry to be of similar age, gender, and ethnicity, but not at elevated risk for ECC, received the standard of care (semi-annual FV treatment). Detailed caries examination and treatment records were obtained for all patients from 2009 to 2014. RESULTS:A significant reduction (P < 0.001) in MS levels was observed in the intensive FV treatment group at the 3-month visit compared with baseline. There was no effect of the intensive FV treatment on caries outcome in the anterior teeth, and the overall caries scores were significantly increased on the posterior teeth. CONCLUSION/CONCLUSIONS:The intensive FV regimen appears insufficient to prevent caries relapse in children at high risk for caries.

Like Streptococcus mutans, lactobacilli are commonly isolated from carious sites, although their exact role in caries development remains unclear. This study used mixed-species models to analyze biofilm formation by major groups of oral lactobacilli, including L. casei, L. fermentum, L. rhamnosus, L. salivarius ssp. salivarius, and L. gasseri. The results showed that lactobacilli did not form good biofilms when grown alone, although differences existed between different species. When grown together with S. mutans, biofilm formation by L. gasseri and L. rhamnosus was increased by 2-log (P < 0.001), while biofilms by L. fermentum reduced by >1-log (P < 0.001). L. casei enhanced biofilm formation by ~2-log when grown with S. mutans wild-type, but no such effects were observed with S. mutans deficient of glucosyltransferase GtfB and adhesin P1. Both S. mutans and L. casei in dual-species enhanced resistance to acid killing with increases of survival rate by >1-log (P < 0.001), but drastically reduced the survival rates following exposure to hydrogen peroxide (P < 0.001), as compared to the respective mono-species cultures. When analyzed by RNA-seq, more than 134 genes were identified in S. mutans in dual-species with L. casei as either up- or down-regulated when compared to those grown alone. The up-regulated genes include those for superoxide dismutase, NADH oxidase, and members of the mutanobactin biosynthesis cluster. Among the down-regulated genes were those for GtfB and alternative sigma factor SigX. These results further suggest that interactions between S. mutans and oral lactobacilli are species-specific and may have significant impact on cariogenic potential of the community.

BACKGROUND: The present study assessed the association between periodontal pathogen colonization and the potential risk of developing precancerous lesions of gastric cancer (PLGC) in a clinical setting. METHODS: The present study included 35 newly diagnosed patients with PLGC and 70 age-matched individuals without PLGC. A full-mouth intra-oral examination was performed to assess the periodontal conditions. Stimulated whole saliva and pooled plaque samples were collected to evaluate colonization by Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia and Actinobacillus actinomycetemcomitans and to characterize the oral microbial diversity in the saliva and dental plaque. RESULTS: Compared with the control group, the patients with PLGC experienced a higher prevalence of bleeding on probing (BOP; 31.5% vs. 22.4%, P < 0.05), higher levels of T. denticola (P < 0.01) and A. actinomycetemcomitans (P <0.01), and less bacterial diversity in their saliva (P < 0.01). The final multivariate logistic regression model comprising all key socio-demographic characteristics, oral health behavioral factors and periodontal assessments revealed that elevated colonization with periodontal pathogens, specifically T. forsythia, T. denticola, and A. actinomycetemcomitans, decreased bacterial diversity in the dental plaque, and not flossing teeth regularly were significant predictors of an increased risk of PLGC (P = 0.022). CONCLUSION: The findings of the present study provide new evidence suggesting that periodontal pathogen burdens and bacterial diversity in the oral cavity are important factors contributing to a potential increased risk of developing precancerous gastric lesions.

Bacterial communities are known to play important roles during the developmental stages of insects, but current knowledge of bacteria associated with the midgut of Apisdorsata,the giant Asian honeybee, is limited.Using polymerase chain reaction-denaturing gradient gel electrophoresis analysis (PCR-DGGE) and 16S rRNA sequencing, the aim of this study was to determine the dynamics of bacterialcommunity structure across four A. dorsata life stages in different geographical locations. The results reveal that bacterial diversity increased as the bee progressed through larval stage to newly emerged worker and oldworker. However, in the pupal stage, no bands identified as bacteria couldbe observed. Overall, twobacterial phyla (Proteobacteria and Firmicutes) and four classes (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Bacilli) were identified, but the frequency varied among the different stages and locations. The classes of Gammaproteobacteria and Bacilli dominated among larval, newly emerged worker and old worker developmental stages

More than 37 million people are living with human immunodeficiency virus 1 (HIV), and more people than ever received lifesaving antiretroviral therapy worldwide. HIV-1 infection disrupts the intestinal immune system, leading to microbial translocation and systemic immune activation. We investigated the impact of HIV-1 infection on the GI microbiome and its association with host immune activation. The data indicated that the microbiome was different in HIV-positive and HIV-negative individuals. The initial sequence analysis of saliva indicated that there were major differences in the phyla of Bacteroidetes, Firmicutes, Proteobacteria, and TM7. Phylum Tenericutes was only seen in HIV-positive saliva. At the family level, we identified differences in Streptococcacea, Prevotellaceae, Porphyromonadaceae, and Neisseriaceae, whereas data from various sites in GI tract indicated that Prevotella melaninigencia, Fusobacterium necrophorum, Burkholderia, Bradyrhizobium, Ralstonia, and Eubacterium biforme were predominant but differentially present at various sites. Furthermore, there was a decrease in seven proteins associated with the alternative complement pathway and an increase in 6 proteins associated with the lectin and classical complement pathways. The correlation with a shift in complement pathways suggests that compromised immunity could be responsible for the observed dysbiosis in the GI microbiome.

Halitosis is a common symptom mainly caused by microbial activities in the oral cavity. Here, we used 16S rRNA gene pyrosequencing and metagenomic sequencing to examine oral microbial compositions and their functional variations in children with halitosis. We found that the tongue coating of subjects with halitosis had greater bacterial richness than those of healthy subjects. The relative abundance and prevalence of Leptotrichia wadei and Peptostreptococcus stomatis were higher in tongue coating samples from children with halitosis than those from children without halitosis; Prevotella shahii had higher relative abundance and prevalence in saliva samples from children with halitosis. We present the first comprehensive evaluation of the co-occurrence networks of saliva and tongue coating communities under healthy and halitosis conditions, and investigated patterns of significant differences between these communities. Moreover, we observed that bacterial genes associated with responses to infectious diseases and terpenoid and polyketide metabolism were enriched in subjects with halitosis, but not in healthy subjects. Hydrogen sulphide (H2S)-related metabolic pathways suggested that there was higher microbial production and less usage of H2S in subjects with halitosis. Thus, the mechanism of halitosis was implied for the first time via metagenomic sequencing.

Oral mucositis (OM) is among the most common, painful, and debilitating toxicities of cancer regimen-related treatment, resulting in the formation of ulcers, which are susceptible to increased colonization of microorganisms. Novel discoveries in OM have focused on understanding the host-microbial interactions, because current pathways have shown that major virulence factors from microorganisms have the potential to contribute to the development of OM and may even prolong the existence of already established ulcerations, affecting tissue healing. Additional comprehensive and disciplined clinical investigation is needed to carefully characterize the relationship between the clinical trajectory of OM, the local levels of inflammatory changes (both clinical and molecular), and the ebb and flow of the oral microbiota. Answering such questions will increase our knowledge of the mechanisms engaged by the oral immune system in response to mucositis, facilitating their translation into novel therapeutic approaches. In doing so, directed clinical strategies can be developed that specifically target those times and tissues that are most susceptible to intervention.

Lactobacilli have been consistently associated with dental caries for decades; however, knowledge of this group of bacteria in the etiology of the disease is limited to quantitative elucidation. Nowadays, explicit identification of oral Lactobacillus species is possible, despite their taxonomic complexity. Here we describe a combined approach involving both cultivation and genetic methods to ascertain and characterize the diversity and abundance of the Lactobacillus population in the oral cavities of children with severe early childhood caries (S-ECC). Eighty 3- to 6-year-old children (40 S-ECC and 40 caries free) who were seeking dental care at the Pediatric Dental Clinic of Bellevue Hospital in New York City were invited to participate in this study. Clinical data on socio-demographic information and oral health behavior were obtained from the primary caregiver. The data included a detailed dental examination, children's medical history, and a questionnaire survey. Combined non-stimulated saliva and supra-gingival plaque samples were collected from each child and cultivated on selective media for quantitative measures of lactobacilli levels. The procedure for Lactobacillus species screening will include the random selection of 50 colonies per plate, extraction of DNA from each colony, and genotyping by arbitrarily primed polymerase chain reaction (AP-PCR). Each unique Lactobacillus AP-PCR genotype will be selected for taxonomic assessment by 16S rRNA gene sequencing analysis. Lactobacillus species will be identified by comparing the 16S rRNA sequences with the Ribosomal Database and the Human Oral Microbiome Database. Meanwhile, the same set of clinical samples will be independently subjected to genomic DNA isolation, 16S rRNA amplification with Lactobacillus genus-specific primers, sequencing, and taxonomic identification, both at genus and species levels with a customized pipeline. The distribution and phylogenetic differences of these Lactobacillus species will be compared between children with or without S-ECC. One of the main objectives of this study is to establish a study protocol for the identification and characterization of lactobacilli in the oral cavity. Future caries risk assessments can include lactobacilli counts (quantitative) and the presence/absence of specific cariogenic genetic signatures of a Lactobacillus species (qualitative) associated with S-ECC.