Faculty Bibliography

Oral Diseases (2012) Objective: Infection has been hypothesized as a contributing factor to bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ). The objective of this study was to determine the bacterial colonization of jawbone and identify the bacterial phylotypes associated with BRONJ. Materials and methods: Culture-independent 16S rRNA gene-based molecular techniques were used to determine and compare the total bacterial diversity in bone samples collected from 12 patients with cancer (six, BRONJ with history of BP; six, controls without BRONJ, no history of BP but have infection). Results: Denaturing gradient gel electrophoresis profile and Dice coefficient displayed a statistically significant clustering of profiles, indicating different bacterial population in BRONJ subjects and control. The top three genera ranked among the BRONJ group were Streptococcus (29%), Eubacterium (9%), and Pseudoramibacter (8%), while in the control group were Parvimonas (17%), Streptococcus (15%), and Fusobacterium (15%). H&E sections of BRONJ bone revealed layers of bacteria along the surfaces and often are packed into the scalloped edges of the bone. Conclusion: This study using limited sample size indicated that the jawbone associated with BRONJ was heavily colonized by specific oral bacteria and there were apparent differences between the microbiota of BRONJ and controls.

We report a clinical study that examines whether HIV infection affects Streptococcus mutans colonization in the oral cavity. Whole stimulated saliva samples were collected from 46 HIV-seropositive individuals and 69 HIV-seronegative control individuals. The level of S. mutans colonization was determined by conventional culture methods. The genotype of S. mutans was compared between 10 HIV-positive individuals before and after highly active antiretroviral therapy (HAART) and 10 non-HIV-infected control individuals. The results were analyzed against viral load, CD4+ and CD8+ T-cell counts, salivary flow rate, and caries status. We observed that S. mutans levels were higher in HIV-infected individuals than in the non-HIV-infected control individuals (p = 0.013). No significant differences in S. mutans genotypes were found between the two groups over the six-month study period, even after HAART. There was a bivariate linear relationship between S. mutans levels and CD8+ counts (r = 0.412; p = 0.007), but not between S. mutans levels and either CD4+ counts or viral load. Furthermore, compared with non-HIV-infected control individuals, HIV-infected individuals experienced lower salivary secretion (p = 0.009) and a positive trend toward more decayed tooth surfaces (p = 0.027). These findings suggest that HIV infection can have a significant effect on the level of S. mutans, but not genotypes.

ABSTRACT: BACKGROUND: Bacterial infections have been linked to malignancies due to their ability to induce chronic inflammation. We investigated the association of oral bacteria in oral squamous cell carcinoma (OSCC/tumor) tissues and compared with adjacent non-tumor mucosa sampled 5 cm distant from the same patient (n = 10). By using culture-independent 16S rRNA approaches, denaturing gradient gel electrophoresis (DGGE) and cloning and sequencing, we assessed the total bacterial diversity in these clinical samples. RESULTS: DGGE fingerprints showed variations in the band intensity profiles within non-tumor and tumor tissues of the same patient and among the two groups. The clonal analysis indicated that from a total of 1200 sequences characterized, 80 bacterial species/phylotypes were detected representing six phyla, Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, Actinobacteria and uncultivated TM7 in non-tumor and tumor libraries. In combined library, 12 classes, 16 order, 26 families and 40 genera were observed. Bacterial species, Streptococcus sp. oral taxon 058, Peptostreptococcus stomatis, Streptococcus salivarius, Streptococcus gordonii, Gemella haemolysans, Gemella morbillorum, Johnsonella ignava and Streptococcus parasanguinis I were highly associated with tumor site where as Granulicatella adiacens was prevalent at non-tumor site. Streptococcus intermedius was present in 70% of both non-tumor and tumor sites. CONCLUSIONS: The underlying changes in the bacterial diversity in the oral mucosal tissues from non-tumor and tumor sites of OSCC subjects indicated a shift in bacterial colonization. These most prevalent or unique bacterial species/phylotypes present in tumor tissues may be associated with OSCC and needs to be further investigated with a larger sample size.

Understanding of the human microbiome continues to grow rapidly; however, reports on changes in the microbiome after HIV infection are still limited. This review surveys the progress made in methodology associated with microbiome studies and highlights the remaining challenges to this field. Studies have shown that commensal oral, gut, vaginal, and penile bacteria are vital to the health of the human immune system. Our studies on crosstalk among oral and gastrointestinal soluble innate factors, HIV, and microbes indicated that the oral and gut microbiome was altered in the HIV-positive samples compared to the negative controls. The importance of understanding the bacterial component of HIV/AIDS, and likelihood of "crosstalk" between viral and bacterial pathogens, will help in understanding the role of the microbiome in HIV-infected individuals and facilitate identification of novel antiretroviral factors for use as novel diagnostics, microbicides, or therapeutics against HIV infection.

Oral Diseases (2011) doi: 10.1111/j.1601-0825.2011.01848.x Objective: Oral infection is considered to play a critical role in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ), and antibiotic therapy has become a mainstay of BRONJ therapy. This study was aimed to investigate the effect of antibiotics on bacterial diversity in BRONJ tissues. Materials and methods: The bacterial profile from soft tissues associated with the BRONJ lesion was determined using 16S rRNA-based denaturing gradient gel electrophoresis (DGGE) and sequencing. Twenty BRONJ subjects classified as stage 0-2 were enrolled in this study, and patient groups were divided into an antibiotic cohort (n = 10) treated with systemic antibiotic and a non-antibiotic cohort (n = 10) with no prior antibiotic therapy. Results: The DGGE fingerprints indicated no significant differences in bacterial diversity of BRONJ tissue samples. Patients on antibiotics had higher relative abundance of phylum Firmicutes with bacterial species, Streptococcus intermedius, Lactobacillus gasseri, Mogibacterium timidum, and Solobacterium moorei, whereas patients without antibiotics had greater amounts of Parvimonas micra and Streptococcus anginosus. Thirty percent of bacterial populations were uncultured (yet-to be cultured) phylotypes. Conclusion: This study using limited sample size indicated that oral antibiotic therapy may have a limited efficacy on the bacterial population associated with BRONJ lesions

Bisphosphonates (BPs) are the standard of care for patients with metastatic cancer and multiple myeloma to prevent skeletal complications (e.g., severe bone pain, pathologic fracture, etc.) and to treat osteoporosis. The cause and effect relationship between BPs and BP-related osteonecrosis of the jaws (BRONJ) is not well established. Current research suggests that bacterial biofilms may play a significant role in the pathogenesis of BRONJ. Recently, we have shown that BRONJ lesions are heavily colonized by oral bacteria and present many clinical challenges as they are difficult to culture and antibiotic resistance may result in misguided antibiotic therapy. Here we highlight the crosstalk among the oral bacteria and host immune response in BRONJ subjects. Using 16S rDNA molecular technique we characterize the total bacterial profile of BRONJ, BP and control subjects. Denaturing gradient gel electrophoresis cluster analysis revealed three clusters each representing the three groups, control, BP and BRONJ indicating that the microbiome present in tissue samples was distinct to each group. DGGE band pattern indicated that the BRONJ group had less bacterial diversity as compared to control indicating that high abundance of specific bacteria colonizing the BRONJ lesion. 16S sequencing and clonal analysis showed 6 phyla in all three groups. The phylum Firmicutes was predominant in BRONJ group (72%) followed by BP group (70%) as compared to control group (59%). The Chi-square test also showed significant differences in percent relative distribution of phyla, between control/BP groups (p<0.001), control/BRONJ (p<0.001) and BP/BRONJ (p<0.05). There was significantly increase in the gram positive bacteria in BRONJ group. PCR Array analysis indicated that the host genes responsible for antibacterial response such as MPO, CTSG, and NOD2 were significantly down regulated. Deficient innate immune responses to microorganisms together with poor healing and repair provide continuous opportunities for expanding!

AIM: The effect of photodynamic antimicrobial chemotherapy (PACT) on oral biofilms was evaluated. METHODS: Biofilms formed in vitro were treated with sensitizer (S) and/or light (L) in the test (S+L+) and control (S-L-, S+L-, S-L+) groups. Additionally, 21 volunteers wore intraoral devices and the biofilms formed on each side of the device were referred to as S+L+ or S-L- groups. RESULTS: Significant decreases in the viability of in vitro biofilms were observed after PACT. PACT was ineffective in inhibiting multi-species biofilms formed in situ. CONCLUSION: PACT was effective on in vitro biofilms and was ineffective on in situ biofilms.

A nonthermal low temperature air plasma jet is characterized and applied to study the plasma effects on oral pathogens and biofilms. Experiments were performed on samples of six defined microorganisms' cultures, including those of gram-positive bacteria and fungi, and on a cultivating biofilm sample of Streptococcus mutans UA159. The results show that the plasma jet creates a zone of microbial growth inhibition in each treated sample; the zone increases with the plasma treatment time and expands beyond the entire region directly exposed to the plasma jet. With 30s plasma treatment twice daily during 5 days of biofilm cultivation, its formation was inhibited. The viability of S. mutans cells in the treated biofilms dropped to below the measurable level and the killed bacterial cells concentrated to local regions as manifested by the fluorescence microscopy via the environmental scanning electron microscope. The emission spectroscopy of the jet indicates that its plasma effluent carries an abundance of reactive atomic oxygen, providing catalyst for the observed plasma effect. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3606486]

In oral cavity chronic inflammation has been observed at various stages of oral squamous cell carcinomas (OSCC). This inflammation could result from persistent mucosal or epithelial cell colonization by microorganisms. There is an increasing evidence of the involvement of oral bacteria in inflammation and warrant further studies on the association of bacteria in the progression of OSCC. The objective of this study was to evaluate the diversity and relative abundance of bacteria in the saliva of subjects with OSCC. Using 454 parallel DNA sequencing, approximately 58,000 PCR amplicons that span the V4-V5 hypervariable region of ribosomal RNAs from 5 subjects were sequenced. Members of 8 phyla (divisions) of bacteria were detected. The majority of classified sequences belonged to phyla, Firmicutes (45%) and Bacteroidetes (25%). Further, a total of 52 different genera containing approximately 860 (16.51%) known species were identified, 1077 (67%) sequences belonged to various uncultured bacteria or unclassified group. The species diversity estimates obtained with abundance-based coverage estimators (ACE) and Chao1 were greater than published analyses of other microbial profiles from the oral cavity. Fifteen unique phylotypes were present in all three OSCC subjects