Reliability of MALDI-TOF mass spectrometry to identify oral isolates of Streptococcus salivarius and Lactobacillus spp.

OBJECTIVE: The aim of this study is to evaluate the performance of MALDI-TOF mass spectrometry in identifying bacteria isolated in the oral cavity known to be of probiotic interest. DESIGN: We evaluated Bruker MALDI Biotyper for the identification of 92 clinical oral isolates of probiotic interest (31 Streptococcus salivarius and 61 Lactobacillus spp.) by comparing direct colony method with on-plate formic acid extraction. Isolates were previously identified by use of biochemical methods and molecular biology. RESULTS: Using the manufacturer's suggested genus and species level cutoff scores, the direct colony method identified 42 (45.7%) isolates at the genus level and 35 (38%) at the species level while the on-plate extraction method correctly identified 90 (97.8%) isolates at the genus level and 82 (89.1%) at the species level. The difference between the two methods was statistically significant at the genus and species levels (P ≤ 0.0001). After dividing the isolates into two subgroups, the analysis was repeated. The direct colony method identified correctly all isolates of Streptococcus salivarius at the species level. In contrast, the direct colony method allowed the identification of only 11 (18%) lactobacilli at the genus level and 4 (6.6%) at the species level. The on-plate extraction method was statistically (P ≤ 0.0001) more efficient since 59 (96.7%) lactobacilli were identified at the genus level and 51 (83.6%) at the species level. CONCLUSIONS: MALDI Biotyper can efficiently identify Streptococcus salivarius regardless of the preparative method but on-plate extraction is superior to direct colony method for the identification of lactobacilli.

Primitive Squamous Cell Carcinoma of Pterygopalatine Fossa.

Primitive tumors of pterygopalatine fossa (PPF) are often benign tumors or extension of a malignant sinonasal tract. Primitive tumors may rarely occur in PPF.The authors present a 71-year-old woman with a 6-month history of left cranial nerve palsy. Magnetic resonance imaging and positron emission tomography-computed tomography showed an enhancing isolated lesion at the PPF. A transmaxillary biopsy was performed, leading to diagnosis of primitive squamous cell carcinoma. The patient underwent radiotherapy treatment.Primitive tumors of PPF are rare and diagnosis may be difficult. Endoscopic access for diagnosis can be performed. Squamous cell carcinoma occurring in PPF is associated with poor prognosis.

Effect of xylitol on an in vitro model of oral biofilm.

PURPOSE: The aim of the present study was to examine whether xylitol, at different concentrations, inhibits the formation of an experimental model of oral biofilm. MATERIALS AND METHODS: Biofilms of six bacterial species (Streptococcus mutans, Streptococcus sobrinus, Lactobacillus rhamnosus, Actinomyces viscosus, Porphyromonas gingivalis and Fusobacterium nucleatum) were prepared on hydroxyapatite (HA) discs according to the Zürich Biofilm Model. Xylitol was tested at two concentrations, 1% and 3%. At the end of their designated incubation times, some HA discs were destined for confocal laser scanning microscopy (CLSM) and the others were harvested using a sterile surgical instrument. Aliquots of harvested biofilms were diluted and plated onto specific media. After a 48-h anaerobic incubation at 37 degrees C, the colony-forming units (CFUs) were counted. RESULTS: CLSM images showed that only a small amount of isolated bacteria was observed on the surface of HA discs. Culture of harvested biofilms showed an inhibition in the growth of different species included in the biofilms. CONCLUSIONS: Xylitol has a clear inhibitory effect on the formation of the experimental biofilms. This study shows that xylitol is not only efficient in inhibiting the acid production of cariogenic bacteria, but also in preventing the formation of a multispecies biofilm; it confirms the relevance of the use of this polyol for the prevention of oral diseases caused by dental plaque.

Effect of three nickel-titanium rotary file techniques on infected root dentin reduction.

OBJECTIVE: This study compared the bacterial reduction of in vitro infected root canals after instrumentation by 3 nickel-titanium (NiTi) rotary files with different taper and diameter versus manual stainless steel files. STUDY DESIGN: Sixty-four single-rooted human teeth were infected with a suspension of Streptococcus sanguis measured by optical density. Teeth were divided randomly into 4 groups of 16 and prepared with Flexofiles, GT rotary files, HERO 642, and ProFile. Bacterial samplings were performed before (S1), during (S2-S3), and after (S4) instrumentation. RESULTS: All techniques significantly reduced the number of bacterial cells in the root canals (P < .05). There was no significant difference between NiTi and manual instrumentation at S2, S3, or S4. Concerning bacterial reduction, the results suggest that a manual stainless steel file preparation is as efficient as a NiTi rotary instrumentation. CONCLUSION: Regardless of the root canal preparation technique, its taper, and diameter, the root dentin remained infected and was not bacteria-free at the end of the experiment.