Persistent extra-radicular bacterial biofilm in endodontically treated human teeth: scanning electron microscopy analysis after apical surgery.

Biofilms are the main cause of endodontic failures. Even the best executed endodontic treatment can fail, when the infection is resistant to treatment or when it is located in inaccessible areas, such as the external surface of the root apex. The purpose of this study was to evaluate, by scanning electron microscopy, the presence of bacterial biofilm on endodontically treated teeth considered clinical failures and suitable for apical surgery. Root apices were collected from 20 teeth undergoing apical surgery and one negative control and analyzed under SEM. Digital photomicrographs of the root apices of 21 specimens at different magnifications were taken. Data were analyzed using descriptive statistics. Apical biofilms were observed in 100% of root canal treatments considered endodontic failure. Topographical analysis of the root apices revealed areas of resorption, microcracks, and apical foramina in 90%, 80%, and 50% of cases, respectively. Within the limits of this study, it can be concluded that endodontic failures present bacterial biofilm in areas inaccessible to conventional endodontic treatment, such as the external surfaces of the root apex.

Characterization of antimicrobial photodynamic therapy-treated Streptococci mutans: an atomic force microscopy study.

UNLABELLED: Abstract Objective: The aim of the present study was to examine the size and shape of Streptococcus mutans bacterial cells of infected dentin substrate subjected to photodynamic therapy (PDT) using atomic force microscopy (AFM). BACKGROUND DATA: New trends in the application of AFM have been developed in the field of dentistry, making AFM a useful technique in high resolution imaging of biological structures and processes. MATERIALS AND METHODS: PDT was completed using an efficient light-emitting diode source (LED - λ=620-660 nm) with total light dose of 94 J/cm(2) in the presence of the photosensitizer toluidine blue O (TBO). Dentin specimens were immersed in brain heart infusion (BHI) broth inoculated with S. mutans for 5 days to induce caries in vitro. After demineralization, the samples were subjected to a series of treatments in which carious dentin infected by S. mutans was exposed to 0.9% sodium chlorite (NaCl) solution (control) for 10 min, or subjected to PDT-TBO photosensitizer followed by light exposure (energy density of 94 J/cm(2)). RESULTS: Three-dimensional (3-D) images and cross-sectional measurements showed rod and diplococcic cell shapes. Photoinactivated bacterial cells did not differ from the control with respect to their cross-sectional shape, but they did show a reduction in size. CONCLUSIONS: Photodynamic therapy decreased the diameter of S. mutans cells and AFM may be used as a technique for bacterial cell analysis.

Effect of subinihibitory and inhibitory concentrations of Plectranthus amboinicus (Lour.) Spreng essential oil on Klebsiella pneumoniae.

We evaluated the antimicrobial activity and some mechanisms used by subinhibitory and inhibitory concentrations of the essential oil, obtained from leaves of Plectranthus amboinicus, against a standard strain of Klebsiella pneumoniae and 5 multiresistant clinical isolates of the bacteria. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), the rate of kill and the pH sensitivity of the essential oil were determined by microdilution tests performed in 96-well plates. Subinhibitory and inhibitory concentrations of the essential oil were tested in order to check its action on K. pneumoniae membrane permeability, capsule expression, urease activity and cell morphology. The MIC and MBC of the essential oil were 0.09±0.01%. A complete inhibition of the bacterial growth was observed after 2 h of incubation with twice the MIC of the essential oil. A better MIC was found when neutral or alkaline pH broth was used. Alteration in membrane permeability was found by the increase of crystal violet uptake when the bacteria were incubated with twice the MIC levels of the essential oil. The urease activity could be prevented when all the subinhibitory concentrations were tested in comparison to the untreated group (p<0.001). Alteration of the bacterial morphology besides inhibition of the capsule expression was verified by atomic force microscopy, and Anthony's stain method, respectively. Our data allow us to conclude that the essential oil of P. amboinicus can be a good candidate for future research.

Biofilm production by clinical Staphylococci strains from canine otitis

This study determined the species of 54 staphylococci isolates from canine otitis and their ability to produce biofilm through the Congo red agar method, confirmed by scanning electron microscopy. The most frequently identified species were S. intermedius and S. simulans. Results showed that 30% of the strains were biofilm producers.