Bacterial biofilm in salivary gland stones: Cause or consequence?

OBJECTIVE: The pathogenesis of salivary calculi is not yet clear; however, 2 theories have been formulated: (1) "the classic theory," based on calcium microdeposits in serous and ductal acinous cells, successively discharged into the ducts; (2) "the retrograde theory," based on a retrograde migration of food, bacteria, and so on from the oral cavity to the salivary duct. The aim of the present study is to highlight the role of bacteria and biofilm in stone formation. STUDY DESIGN: Case series without comparison. SETTING: Laboratory of the Department of Anatomical Pathology. SUBJECTS AND METHODS: Traditional optic microscopy and scanning electron microscopy were carried out on 15 salivary gland calculi that were collected from 12 patients. A qPCR (quantitative real-time polymerase chain reaction) assay was performed to highlight the presence of bacterial DNA on each stone. RESULTS: Optic microscopy showed formations that-due to their size, shape, and Gram and Giemsa staining-seemed to be Gram-positive bacterial cells. PAS- (periodic acid-Schiff) and alcian-PAS-positive staining matrix was present around them. The ultrastructural observation of the material processed for scanning electron microscopy showed the presence of structures resembling bacterial cells in the middle of the stones, surrounded by soft, amorphous material. Results of qPCR showed the presence of bacterial DNA in the internal part of the tissue sample. CONCLUSIONS: The presence of bacteria and/or bacterial products resembling biofilm in salivary gland stones supports the "retrograde theory." This evidence may support the hypothesis that biofilm could be the causative effect of lithiasic formations

Microbial surfactants: fundamentals and applicability in the formulation of nano-sized drug delivery vectors

Microbial surfactants, so-called biosurfactants, comprise a wide variety of structurally distinct amphipathic molecules produced by several microorganisms. Besides exhibiting surface activity at the interfaces, these molecules present powerful characteristics including high biodegradability, low toxicity and special biological activities (e.g. antimicrobial, antiviral, anticancer, among others), that make them an alternative to their chemical counterparts. Several medical-related applications have been suggested for these molecules, including some reports on their potential use in the formulation of nano-sized drug delivery vectors. However, despite their promises, due to the generalized lack of knowledge on microbial surfactants phase behavior and stability under diverse physicochemical conditions, these applications remain largely unexplored, thus representing an exciting field of research. These nano-sized vectors are a powerful approach towards the current medical challenges regarding the development of efficient and targeted treatments for several diseases. In this review, a special emphasis will be given to nanoparticles and microemulsions. Nanoparticles are very auspicious as their size, shape and stability can be manipulated by changing the environmental conditions. On the other hand, the easiness of formulation, as well as the broad possibilities of administration justifies the recent popularity of the microemulsions. Notwithstanding, both vector types still require further developments to overcome some critical limitations related with toxicity and costs, among others. Such developments may include the search for other system components, as the microbial surfactants, that can display improved features.The author acknowledges the financial support from the Strategic Project PEst-OE/EQB/LA0023/2013 and project ref. RECI/BBB-EBI/0179/2012 (project number FCOMP-01-0124-FEDER-027462) funded by Fundacao para a Ciencia e a Tecnologia