Effect of quorum sensing molecules and natamycin on biofilms of Candida tropicalis and other yeasts isolated from industrial juice filtration membranes.

AIMS: Cells limit the cell number of dense biofilms by releasing self-inhibitory molecules. Here, we aim to assess the effectiveness of yeast quorum sensing (QS) molecules and the antifungal agent natamycin against yeast biofilms of strains commonly isolated from fruit juice ultrafiltration membranes. METHODS AND RESULTS: Yeast QS molecules, such as tyrosol, 2-phenylethanol and farnesol, were detected by solvent extraction and HS-SPME GC-MS in Candida tropicalis cultures. The effect of QS molecules on mono- and multispecies biofilms formed by Rhodotorula mucilaginosa, C. tropicalis, Candida krusei and Candida kefyr was evaluated by plate count and epifluorescence microscopy. Farnesol caused a decrease in cell number and disrupted mono- and multispecies yeast biofilms during adhesion (0·6 mmol l-1 ). 2-phenyl ethanol 1·2 mmol l-1 stimulated biofilm density and increased cell number in both mono- and multispecies biofilms, while tyrosol did not show effects when tested against C. tropicalis biofilms (0·05-1·2 mmol l-1 ). Natamycin caused a strong decrease in cell number and disruption of biofilm structure in C. tropicalis biofilms at high concentrations (0·3-1·2 mmol l-1 ). The combination of farnesol 0·6 mmol l-1 and natamycin at 0·01 mmol l-1 , the maximum concentration of natamycin accepted for direct addition into fruit juices, effectively reduced cell counts and disrupted the structure of C. tropicalis biofilms. CONCLUSION: Farnesol 0·6 mmol l-1 significantly increased the inhibition exerted by natamycin 0·01 mmol l-1 (~5 ppm) reducing biofilm development from juice on stainless steel surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: These results support the use of QS molecules as biofilm inhibitors in beverages and would certainly inspire the design of novel preservative and cleaning products for the food industry based on combinatory approaches.

Bilateral mandibular fourth molars: A case report.

INTRODUCTION: Fourth molars are supernumerary teeth located distal to the third molars that may cause local alterations. Therefore an adequate diagnosis and treatment are essential. Removal of the supernumerary tooth and, in selected cases, maintenance of the tooth on the arch and frequent observation are the preferred treatments. If the extraction is recommended, it should be performed carefully by experienced oral surgeons to prevent damage to the anatomical structures. OBSERVATION: The oral examination of a 26-year-old woman revealed a left partially impacted mandibular molar responsible for pain and infection. Although it was assumed it was a third molar, the panoramic radiograph showed that the real third molar was completely impacted and that two partially impacted mandibular fourth molars were present bilaterally. Both of them were removed without complications and the left third molar was extracted after fragmentation to avoid any injury of the contiguous inferior alveolar nerve. DISCUSSION: The extraction of the left fourth molars solved the pain. Even if the right fourth molar was asymptomatic, the patient accepted its extraction because of the evident radiographical pericoronitis and to avoid further complications. "Asymptomatic" does not mean absence of disease, but the patient's consent is mandatory before any decision.