Extracellular Fibrils of Pathogenic Yeast Cryptococcus gattii Are Important for Ecological Niche, Murine Virulence and Human Neutrophil Interactions

Cryptococcus gattii, an emerging fungal pathogen of humans and animals, is found on a variety of trees in tropical and temperate regions. The ecological niche and virulence of this yeast remain poorly defined. We used Arabidopsis thaliana plants and plant-derived substrates to model C. gattii in its natural habitat. Yeast cells readily colonized scratch-wounded plant leaves and formed distinctive extracellular fibrils (40–100 nm diameter ×500–3000 nm length). Extracellular fibrils were observed on live plants and plant-derived substrates by scanning electron microscopy (SEM) and by high voltage- EM (HVEM). Only encapsulated yeast cells formed extracellular fibrils as a capsule-deficient C. gattii mutant completely lacked fibrils. Cells deficient in environmental sensing only formed disorganized extracellular fibrils as apparent from experiments with a C. gattii STE12α mutant. C. gattii cells with extracellular fibrils were more virulent in murine model of pulmonary and systemic cryptococcosis than cells lacking fibrils. C. gattii cells with extracellular fibrils were also significantly more resistant to killing by human polymorphonuclear neutrophils (PMN) in vitro even though these PMN produced elaborate neutrophil extracellular traps (NETs). These observations suggest that extracellular fibril formation could be a structural adaptation of C. gattii for cell-to-cell, cell-to-substrate and/or cell-to- phagocyte communications. Such ecological adaptation of C. gattii could play roles in enhanced virulence in mammalian hosts at least initially via inhibition of host PMN– mediated killing

Antimicrobial activity of extracts of calcium hydroxide points.

The purpose of this study was to evaluate in vitro the antibacterial effect of calcium hydroxide points by using a broth dilution test. Extracts of calcium hydroxide points and a calcium hydroxide paste (Calasept) were tested by using 2 facultative anaerobic bacteria, Streptococcus mutans (ATCC 27352) and Enterococcus faecalis (ATCC 29212). Saline solution was used as a control. Each tested agent was kept in contact with the bacterial species used for the experiment for 5 minutes, 1 hour, 1 day, 2 days, and 5 days. Results showed that Calasept paste was effective in killing the tested bacteria, whereas calcium hydroxide points and saline showed bacterial survival in all experimental periods. It was concluded that calcium hydroxide points extract is not an effective antimicrobial agent against the tested bacteria.King Saud Universit

Two root canals in a maxillary central incisor with enamel hypoplasia.

Presented is a case of enamel hypoplasia of a maxillary central incisor which was referred for endodontic therapy. Radiographical examination revealed a tooth having one root and two canals. Endodontic therapy was performed under aseptic conditions.King Saud Universit

The prevalence of two canals in mesial root of endodontically treated maxillary first molars among a Saudi Arabian sub-population.

The aim of this in vivo study was to assess the incidence of two root canals in the mesial root of the endodontically treated permanent maxillary first molars of a Saudi Arabian sub-population. A clinical study of 352 root-canal treated permanent maxillary first molars was conducted. The teeth were examined clinically and radiographically. The results showed that 23.3 % of the examined teeth had two canals in the mesial root (17.0 % with one apical foramen and 6.3 % with two separate foramens). The occurrence of two canals in the mesial root of the maxillary first molar of a Saudi Arabian sub-population was within the normal range.King Saud Universit

Retrieval of separated instruments using a combined method with a modified vista dental tip

Biomechanical preparation of the entire root canal system is one of the most important procedures in endodontic treatment. Separation of instruments while preparing root canals presents a compromised situation in which a biologically inert segment is left behind with potential contamination that has the ability to affect the healing process. Management of this procedural error is tedious and requires creativity as well as clinical knowledge and skills. In this report, we demonstrated two cases with separated instrument in which a combined technique of ultrasonic method with microtube tube method was used to retrieve the separated tips using a modified Vista dental tip

Mandibular second premolar with three root canals: Report of a case

Location and thorough instrumentation of all the canals in the root of a diseased tooth normally ensure success of the endodontic therapy. Presented is a case of mandibular second premolar which was referred for endodontic therapy. Clinical and radiographic examination revealed inadequate root canal filling. Three canals were located. Endodontic therapy was performed under aseptic conditions.King Saud Universit

Evaluation of the effect of delayed management of traumatized permanent teeth.

This investigation studied the complication that could arise from delayed management of traumatized permanent teeth. Patients reported to the primary care clinic at the College of Dentistry, King Saud University, seeking treatment of traumatized anterior teeth were evaluated. Esthetic consideration (64 patients) and pain, swelling, or discomforts (50 patients) were the main reasons the patients came to the clinic. Clinical and radiographic examinations, as well as history of the trauma, were recorded. It was found that most of the patients had a treatment delay exceeding 1 month. Initial pulp exposure resulted in 100% pulp necrosis. When a fracture involved both enamel and dentin, the frequency of pulp necrosis was 53%. External root resorption and pulp calcification were seen in few teeth. It was concluded that the figures for pulp necrosis could be misleading, because there might have been a bias when only patients with problems sought treatment. In addition, a trauma awareness educational program should be developed to encourage parents and the public to seek immediate dental treatment. Furthermore, a proper diagnostic test for pulp and periodontal complication should be done in patients with initially nontreated dental injuries.King Saud Universit