Special edition on oral infections and microbiology

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SEM Image of Candida Albicans Biofilms on Plastic Coupons

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Reduced level of induced endocytosis in Candida albicans sap7 mutants

Poster Session: Scientific Groups - 90. Microbiology/Immunology III: no. 655OBJECTIVE: To investigate the effect of C. albicans SAP7 gene in induced endocytosis in Candida-epithelial cell interactions. METHOD: In this study, C. albicans sap7 mutant strain was constructed in our laboratory by a PCR – based gene disruption method. In the endocytosis assay, the number of C. albicans cells that were cell-associated with and endocytosed by OKF6/TERT2 was determined using differential fluorescence assay with minor modifications. Briefly, conflucent OKF6/TERT2 cells were infected with 1×105 Candida cells for 3 h incubation. After removing nonadherent organisms, the cells were fixed with 3% paraformaldehyde. The adherent but not endocytosed ...postprin

Characterization of Actinobacillus actinomycetemcomitans isolated from young Chinese aggressive periodontitis patients

Objective: This study characterized Actinobacillus actinomycetemcomitans isolates from young Chinese aggressive periodontitis patients. Methods: Subgingival plaque samples (two/subject) were collected from diseased subjects < 25 years old (n = 9, mean age 21.1 ± 1.6 years) and age-matched periodontitis-free controls (n = 47, mean age 22.0 ± 1.1 years). Selective and anaerobic culture were used. The serotype, leukotoxin gene (ltx) operon promoter and the cytolethal distending toxin (cdt) genes complex of the A. actinomycetemcomitans isolates were investigated. Effects of the isolates on non-keratinizing periodontal ligament epithelial cells monolayer were studied. Results: Diseased subjects had significantly higher full-mouth bleeding score (p = 0.002) and total viable counts from plaque samples (7.2 × 10 6 vs. 2.1 × 105 CFU/paperpoint, p < 0.005). A. actinomycetemcomitans was isolated from 67%/56% or 6%/4% of diseased or controls subject/sites, respectively (p < 0.001). The proportion of A. actinomycetemcomitans isolatable from aggressive periodontitis or periodontitis-free associated subgingival plaque was low (0.7% vs. 0.1%, p < 0.02). The serotype of the isolates was characterized. All isolates possessed 652-like ltx gene promoter and all but one serotype c isolate from a diseased patient had intact cdtABC genes. That particular strain appeared to confer the least cellular damages on periodontal ligament epithelial monolayer compared to others. Conclusion: This preliminary study confirmed the notion of increased prevalence and quantity of A. actinomycetemcomitans associated with aggressive periodontitis in young patients. The overall ltx promoter and cdt characteristics of the A. actinomycetemcomitans isolates, however, were similar among the diseased and control groups. A strain lacking the cdtABC gene appeared to be less damaging to a periodontal ligament epithelial cell model. Further studies therefore are warranted to clarify the pathogenic role and potentials of A. actinomycetemcomitans in aggressive periodontitis. © Blackwell Munksgaard 2005.published_or_final_versio

Actinobacillus actinomycetemcomitans isolated from young Chinese adults with aggressive periodontitis

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Differential Phytate Utilization in Candida species

The present study was undertaken to evaluate and characterize the phytase activity in different Candida species. A total of 113 Candida isolates representing eight species were examined for phytase activity by an agar plate assay using the calcium salt of phytic acid as the sole phosphorus source. A phytase-positive phenotype was identified by the formation of a clear halo around a fungal colony. Cell-bound differential phytase activity was observed in Candida isolates at inter- and intra-species levels. Although phytase activity was not affected by the supplementation of external phosphate in C. albicans, C. dubliniensis, C. glabrata, and C. kefyr, elevated phytase activity was evident in C. guilliermondii, C. krusei, C. parapsilosis, and C. tropicalis in phosphate-free medium. Further characterization showed that, in general, relatively higher phytase activity was observed at more acidic pHs, and the phytase activity increased with incubation temperature, reaching a maximum at 55 or 65°C. Taken together, the findings demonstrated, for the first time, differential phytase activities in different Candida species. Phytase activity may be a contributing factor to fungal survival and proliferation within the human gastrointestinal tract, where nutrients are usually scarce. © 2011 Springer Science+Business Media B.V.link_to_subscribed_fulltex

Survival of methicillin-resistant Staphylococcus aureus on toothbrushes stored under protective covers and sanitizers

Poster PresentationOBJECTIVES: To investigate the survival of methicillin-resistant Staphylococcus aureus on toothbrushes stored under commercially available antimicrobial and non-antimicrobial covers. METHODS: Standardized inocula of methicillin-resistant Staphylococcus aureus (MRSA) ATCC 700698 were prepared and adjusted to a 0.5 McFarland standard (~1.5x108 cfu/mL). A total of 45 toothbrush heads were contaminated with MRSA by submerging in 5mL of bacterial culture and vortexing for three minutes. Toothbrush heads were then stored for 24 hours under a thymol vapor-emitting toothbrush cover (Steripod), standard plastic cover with ventilation holes (Coghlan’s), moisture-absorbent cover (IntelliDent Toothbrush Shield), or ultraviolet light sanitizer (Docooler). Toothbrush heads were vortexed for 15s in 5mL of sterile 0.9% sodium chloride solution, and serial dilutions were performed prior to spiral plating on blood agar. A positive control was included in which toothbrush heads were immediately vortexed to remove bacteria following contamination with the inoculum. Colony-forming units (cfu) were enumerated after overnight aerobic incubation at 37oC. All assays were performed in triplicate. RESULTS: Significant reductions (p<0.001) in MRSA cfu were observed among toothbrush heads stored under all four experimental conditions, compared to the positive control. Survival of MRSA on toothbrush heads stored under standard plastic covers was significantly greater than those on toothbrush heads stored under the thymol vapor-emitting cover (p=0.006), moisture-absorbent cover (p=0.006), and UV sanitizer (p=0.011). Survival of MRSA (~4%) was equivocal on toothbrush heads stored under the latter three conditions. CONCLUSIONS: Survival of MRSA was significantly lowered on toothbrushes stored under the thymol vapor-emitting cover, moisture-absorbent cover, and UV sanitizer. None of the toothbrush covers were able to completely eradicate MRSA following a storage period of 24 hours

Melatonin interferes with the biofilm development in Candida parapsilosis

Poster Session 22 - P2: no. 660OBJECTIVE: To investigate the in vitro effect of melatonin on C. parapsilosis biofilms METHOD: C. parapsilosis ATCC 22019 was grown on YPD agar (1% yeast extract, 2% peptone, 2% dextrose, 2% agar) at 30°C over...link_to_OA_fulltex

Aspirin as an antifungal lock therapy agent

Poster Session - Microbiology/Immunology II: abstract no. 177Journal of Dental Research, 2011, Special Issue B, p. 177Candida biofilms on central venous catheters are one of the commonest nosocomial fungal bloodstream infections. Antifungal lock solutions have been shown to be effective in salvaging indwelling catheters in patients requiring intravenous therapy. Objectives: To determine the activity of aspirin as a lock solution against four Candida biofilms on silicone catheter sections. Methods: Biofilms of Candida albicans, Candida glabrata, Candida krusei and Candida tropicalis were formed on silicone catheters in vitro. The catheters were exposed to lock therapy with aspirin at concentrations of 5 mg/ml – 45 mg/ml, for 2, 4 and 24 hr. Untreated biofilms served as controls. The catheters were then removed and quantified by culture and XTT assays. Results: Significant reduction in CFU counts (approaching 100%) was detected as early as 2 hr in C. albicans biofilms treated with 40 mg/ml aspirin, whereas the same level of reduction was only obtained at 45 mg/ml aspirin, locked for 4 hr in C. glabrata and C. tropicalis (p < 0.05). However, C. krusei only showed 50 % reduction of XTT activities at concentration of 45 mg/ml aspirin, locked for 24 hr. Conclusion: Our results showed that catheter-lock solution of aspirin may be used to salvage catheters infected with C. albicans, C. glabrata, C. tropicalis , but not C. krusei.link_to_OA_fulltextThe 25th IADR-SEA Division Annual Scientific Meeting, Singapore, 28-30 October 2011