Linda E. Choquette

Using high throughput sequencing to explore the biodiversity in oral bacterial communities

High throughput sequencing of 16S ribosomal RNA gene amplicons is a cost-effective method for characterization of oral bacterial communities. However, before undertaking large-scale studies, it is necessary to understand the technique-associated limitations and intrinsic variability of the oral ecosystem. In this work we evaluated bias in species representation using an in vitro-assembled mock community of oral bacteria. We then characterized the bacterial communities in saliva and buccal mucosa of five healthy subjects to investigate the power of high throughput sequencing in revealing their diversity and biogeography patterns. Mock community analysis showed primer and DNA isolation biases and an overestimation of diversity that was reduced after eliminating singleton operational taxonomic units (OTUs). Sequencing of salivary and mucosal communities found a total of 455 OTUs (0.3% dissimilarity) with only 78 of these present in all subjects. We demonstrate that this variability was partly the result of incomplete richness coverage even at great sequencing depths, and so comparing communities by their structure was more effective than comparisons based solely on membership. With respect to oral biogeography, we found inter-subject variability in community structure was lower than site differences between salivary and mucosal communities within subjects. These differences were evident at very low sequencing depths and were mostly caused by the abundance of Streptococcus mitis and Gemella haemolysans in mucosa. In summary, we present an experimental and data analysis framework that will facilitate design and interpretation of pyrosequencing-based studies. Despite challenges associated with this technique, we demonstrate its power for evaluation of oral diversity and biogeography patterns.

Effect of stressful life events on the onset and duration of recurrent aphthous stomatitis.

BACKGROUND Recurrent aphthous stomatitis (RAS) is a common and painful oral mucosal disease. Possible etiologies include genetics, vitamin deficiencies, trauma, immune dysfunction, and stress. The goal of this study was to examine the relationship between the occurrence, type, and magnitude of stressful events and the onset and duration of RAS episodes. METHODS One hundred and sixty subjects with a history of RAS completed a weekly phone survey for up to 1 year, providing data on the occurrence of RAS episodes and details of any stressful events they experienced during the previous week. During RAS episodes, subjects also completed daily paper diaries that recorded incidence and duration of the RAS episode. Stressful events were quantified using the validated Recent Life Changes Questionnaire (RLCQ) and were classified as mental or physical stressors. RESULTS Stressful life events were significantly associated with the onset of RAS episodes (P < 0.001), however, not with the duration of the RAS episodes. Experiencing a stressful life event increased the odds of an RAS episode by almost three times (OR = 2.72; 95% CI = 2.04-3.62). When controlled for each other, mental stressors had a larger effect (OR = 3.46, 95% CI = 2.54-4.72) than physical stressors (OR = 1.44; 95% CI = 1.04-1.99) on the occurrence of RAS episodes. RAS episodes did not occur more frequently or last longer with increasing stress severity. CONCLUSIONS In patients with a history of RAS, stressful events may mediate changes involved in the initiation of new RAS episodes. Mental stressors are more strongly associated with RAS episodes than physical stressors.

Randomized double-blind placebo-controlled trial of celecoxib for oral mucositis in patients receiving radiation therapy for head and neck cancer

OBJECTIVES Oral mucositis (OM) is a painful complication of radiation therapy (RT) for head and neck cancer (H&NC). OM can compromise nutrition, require opioid analgesics and hospitalization for pain control, and lead to treatment interruptions. Based on the role of inflammatory pathways in OM pathogenesis, we investigated effect of cyclooxygenase-2 (COX-2) inhibition on severity and morbidity of OM. METHODS In this double-blind placebo-controlled trial, 40 H&NC patients were randomized to daily use of 200 mg celecoxib or placebo, for the duration of RT. Clinical OM, normalcy of diet, pain scores, and analgesic use were assessed 2-3 times/week by blinded investigators during the 6-7 week RT period, using validated scales. RESULTS Twenty subjects were randomized to each arm, which were similar with respect to tumor location, radiation dose, and concomitant chemotherapy. In both arms, mucositis and pain scores increased over course of RT. Intention-to-treat analyses demonstrated no significant difference in mean Oral Mucositis Assessment Scale (OMAS) scores at 5000 cGy (primary endpoint). There was also no difference between the two arms in mean OMAS scores over the period of RT, mean worst pain scores, mean normalcy of diet scores, or mean daily opioid medication use in IV morphine equivalents. There were no adverse events attributed to celecoxib use. CONCLUSIONS Daily use of a selective COX-2 inhibitor, during period of RT for H&NC, did not reduce the severity of clinical OM, pain, dietary compromise or use of opioid analgesics. These findings also have implications for celecoxib use in H&NC treatment regimens (NCT00698204).

Transient bacteremia induced by dental cleaning is not associated with infection of central venous catheters in patients with cancer

OBJECTIVE The aim of this study was to determine the incidence of bacteremia resulting from dental cleaning and of subsequent established bloodstream infection (BSI) caused by oral microorganisms in patients with cancer with central venous catheters (CVCs). STUDY DESIGN Twenty-six patients with cancer with CVCs and absolute neutrophil count over 1000 cells/µL received dental cleaning without antibiotic prophylaxis. Periodontal status was assessed at baseline by using the Periodontal Screening and Recording (PSR) score. Blood cultures were drawn via the CVCs at baseline, 20 minutes into cleaning, and 30 minutes and 24 hours after cleaning. Medical records were monitored for 6 months. RESULTS Baseline blood culture results were negative in 25 patients. Nine of 25 patients (36%) had positive blood culture 20 minutes into cleaning, all associated with at least 1 microorganism typically found in the mouth. These 9 patients had significantly higher mean PSR score (3.22) compared with the other 16 (2.56; P = .035). These expected bacteremias did not persist, with blood culture results (0/25) at 30 minutes and 24 hours after cleaning showing no positivity (P = .001). There were no cases of CVC-related infection or BSI attributable to dental cleaning. CONCLUSIONS Bacteremia resulting from dental cleaning is transient and unlikely to cause CVC-related infection or BSI in patients with absolute neutrophil count greater than 1000 cells/µL.