http://hdl.handle.net/2262/71 Dental Science 2013-05-12T21:16:13Z http://hdl.handle.net/2262/64712 Title: ENRICHMENT OF MULTILOCUS SEQUENCE TYPING CLADE 1 WITH ORAL CANDIDA ALBICANS ISOLATES IN PATIENTS WITH UNTREATED PERIODONTITIS Author: COLEMAN, DAVID; MC MANUS, BRENDA Abstract: This study investigated the prevalence and cell density of Candida species in periodontal pockets, healthy subgingival sites and in oral rinses of patients with untreated periodontitis. Twenty-one periodontitis patients underwent sampling at two periodontitis sites and for 19/21 patients one periodontally healthy site. Both paper-point and curette sampling techniques were employed. The periodontitis patients and 50 healthy subjects were also sampled by oral rinse. Candida isolates were recovered on CHROMagar Candida medium and representative isolates identified. Candida was recovered from 10/21 (46.7%) periodontitis patients and from 16/50 (32%) healthy subjects. C. albicans predominated in both groups and was recovered from all Candida-positive subjects. Candida-positive periodontitis patients yielded Candida from periodontal pockets with average densities from curette and paper-point samples of 3,528 and 3,910 CFU/sample, respectively, and 1,536 CFU/ml from oral rinses. The majority (18/19) of periodontitis patients’ healthy sites sampled were Candida-negative. The 16 Candida-positive healthy subjects yielded an average of 279 CFU/ml from oral rinses. C. albicans isolates were investigated by multilocus sequence typing (MLST) to determine if specific clonal groups were associated with periodontitis. MLST analysis of 31 C. albicans isolates from periodontitis patients yielded 19 sequence types (STs), 13 of which were novel. Eleven STs belonged to MLST clade 1. In contrast, 16 C. albicans isolates from separate healthy subjects belonged to 16 STs, with four from clade 1. The distribution of STs between both groups was significantly different (p=0.04) and indicates an enrichment of C. albicans isolates in periodontal pockets that warrants a larger study. Description: PUBLISHED; 8th August; Epub ahead of print 2012-01-01T00:00:00Z http://hdl.handle.net/2262/64095 Title: Detection of staphylococcal cassette chromosome mec type XI carrying highly divergent mecA, mecI, mecR1, blaZ, and ccr genes in human clinical isolates of clonal complex 130 methicillin-resistant Staphylococcus aureus. Author: SHORE, ANNA; COLEMAN, DAVID; DEASY, EMILY Abstract: Methicillin resistance in staphylococci is mediated by penicillin binding protein 2a (PBP2a) encoded by mecA on mobile staphylococcal cassette chromosome mec (SCCmec) elements. In this study two clonal complex (CC) 130 methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients in Irish hospitals were identified that were phenotypically PBP2a-positive but lacked mecA by conventional PCR and by DNA microarray screening. The isolates were identified as methicillin-susceptible S. aureus using the GeneXpert real-time PCR assay. Whole-genome sequencing of one isolate (M10/0061) revealed a 30 kb SCCmec element encoding a class E mec complex with highly divergent blaZ-mecA-mecRI-mecI, a type 8 cassette chromosome recombinase (ccr) complex consisting of ccrA1-ccrB3, an arsenic resistance operon and flanking direct repeats (DRs). The SCCmec element was almost identical to SCCmec XI identified by the Sanger Institute in the sequence type 425 bovine MRSA strain LGA251 listed on the website of the International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements. The open reading frames (ORFs) identified within SCCmec XI of M10/0061 exhibited 21-93% amino acid identity to ORFs in GenBank. A third DR was identified ca. 3 kb downstream of SCCmec XI indicating the presence of a possible SCC remnant. SCCmec XI was also identified in the second CC130 MRSA isolate by PCR and sequencing. The CC130 MRSA isolates may be of animal origin as previously reported CC130 S. aureus were predominantly from bovine sources. The highly divergent nature of SCCmec XI relative to other SCCmec elements indicates that it may have originated in another taxon. Description: PUBLISHED 2011-01-01T00:00:00Z http://hdl.handle.net/2262/63996 Title: Distribution of SCCmec-associated phenol-soluble modulin in staphylococci Author: SHORE, ANNA; COLEMAN, DAVID Abstract: The recently described phenol-soluble modulin PSM-mec was detected in S. aureus, S. epidermidis, S. fleuretti, S. hominis, S. pseudintermedius, S. saprophyticus, S. simulans and S. vitulinus from different hosts (humans, goats, dogs, cats, pigs, cattle and turkeys). It was identified in isolates harbouring SCCmec types II, IIA, IIB, IID, III, VIII and in some irregular or truncated elements. Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/63860 Title: Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials Author: DOWLING, ADAM HENRY; FLEMING, GARRY; GRUFFERTY, BRENDAN FRANCIS Abstract: Objectives: To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases. Methods: Twenty-four sound upper premolar teeth with Class II cavities were allocated to three groups (n = 8). Restoration of the teeth involved the placement of an RBC (GrandioSO) in eight oblique increments (Group A) or Groups B and C were restored to within 2 mm of the palatal cusp in a single increment with bulk-fill flowable RBC bases (SDR and x-tra base) before the two occlusal cavity increments were placed with GrandioSO. Buccal and palatal cusp deflections were recorded postirradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in 0.2% basic fuchsin dye for 24 h, sectioned and examined for cervical microleakage Results: The mean total cuspal deflection for the oblique incremental restoration technique was 11.26 (2.56) μm (Group A) and 4.63 (1.19) μm (Group B) and 4.73 (0.99) μm (Group C) for the bulk-fill flowable RBC bases. A significant increase in the mean total cuspal deflection for the incrementally filled GrandioSO compared with the SDR (P = 0.007) and x-tra base (P = 0.005) restored teeth was evident. No significant difference in the cervical microleakage scores were recorded between groups AC (P > 0.05). Conclusions: The bulk-fill flowable RBC bases significantly reduced cuspal deflection compared with a conventional RBC restored in an oblique incremental filling technique with no associated change in cervical microleakage recorded. Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/62424 Title: The crushing truth about glass ionomer restoratives: exposing the standard of the standard Author: FLEMING, GARRY Abstract: Objectives: The compressive fracture strength (CFS) test is the only strength test for glass ionomers (GIs) in ISO 9917-1: 2003. The CFS test was the subject of much controversy in 1990 and has been challenged over its appropriateness and reproducibility and the study aimed to revisit the suitability of the CFS test for GIs. Methods: Groups of 20 (four batches of n = 5) cylinders (6.0 ± 0.1 mm height, 4.0 ±0.1 mm diameter) of three encapsulated GIs were prepared for CFS testing using two mechanical mixing regimes and two operators. The CFS data for each GI restorative were pooled, three-, two- and one-way analyses of variance (ANOVAs) were conducted (p = 0.05) for operator, mixing regime and batch to assess reliability. The data was also analysed according to ISO 9917-1: 2003. Results: The three-way ANOVAs showed a significant interaction of operator × mixing regime × batch (p < 0.017) for two of the three encapsulated GIs. However, no significant effects of operator × mixing regime (p > 0.042), operator × batch (p > 0.332), mixing regime × batch (p > 0.056), operator (p > 0.094), mixing regime (p > 0.118) or batch (p > 0.054) were evident. When examined in batches of five (or ten where appropriate) as specified in ISO 9917-1: 2003, inter- and intra-operator variability were evident. Conclusions: The use of batch-censoring in accordance with ISO 9917-1: 2003 is unsafe when the data scatter reflects a homogenous flaw distribution as it misidentifies operative variability. Despite demonstrating that the CFS test can be performed reliably, the validity of the CFS test for GIs remains under scrutiny. Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/62423 Title: Improving the standard of the standard for glass ionomers: an alternative to the compressive fracture strength test for consideration? Author: FLEMING, GARRY Abstract: Objectives: Three strength tests (compressive, three point flexure and biaxial) were performed on three glass ionomer (GI) restoratives to assess the most appropriate methodology in terms of validity and reliability. The influence of mixing induced variability on the data sets generated were eliminated by using encapsulated GIs Methods: Specimen groups of 40 (eight batches of n = 5) cylinders (6.0 ± 0.1 mm height, 4.0 ±0.1 mm diameter) for compressive testing, bars (25.0 ± 0.1 mm length, 2.0 ± 0.1 mm height, 2.0 ± 0.1 mm width) for three point flexure testing and discs (13.0 ± 0.1 mm diameter, 1.0 ± 0.1 mm thickness) for biaxial testing were randomly prepared by an operator. The strength data sets for each GI restorative were pooled and one-way analyses of variance (ANOVAs) were conducted to compare between GI restoratives (p = 0.05). The coefficient of variation (CoV) values for each test were pooled and a one-way ANOVA was conducted to test for differences between the reliability of the three tests Results: For the GI restoratives, the one-way ANOVA showed significant differences when tested in compression (p = 0.001) but not when tested in three point (p = 0.271) or biaxial (p = 0.134) flexure. The pooled CoV values showed no significant difference between the three strength tests (p = 0.632). Conclusions: The compressive fracture strength test specified for GIs in the International Organisation for Standardisation (ISO 9917-1: 2003) should be replaced and should no longer be advocated for the predictive performance modelling of GI restoratives Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/62416 Title: DNA MICROARRAY GENOTYPING AND VIRULENCE AND ANTIMICROBIAL RESISTANCE GENE PROFILING OF METHICILLIN-RESISTANT Staphylococcus aureus BLOODSTREAM ISOLATES FROM RENAL PATIENTS Author: SHORE, ANNA; COLEMAN, DAVID Abstract: Thirty-six methicillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates from renal patients were genetically characterized by DNA microarray analysis and spa typing. The isolates were highly clonal, belonging mainly to ST22-MRSA-IV. The immune evasion and enterotoxin gene clusters were found in 29/36 (80%) and 33/36 (92%) of isolates, respectively. Description: PUBLISHED 2011-01-01T00:00:00Z http://hdl.handle.net/2262/61635 Title: Base-metal dental casting alloy biocompatibility assessment using a human-derived 3D oral mucosal model Author: MORAN, GARY; MC GINLEY, EMMA LOUISE; FLEMING, GARRY Abstract: Nickel-chromium (Ni-Cr) alloys used in fixed prosthodontics have been associated with type IV nickel-induced hypersensitivity. We hypothesized the full-thickness human-derived oral mucosa model employed for biocompatibility testing of base-metal dental alloys would provide insights into mechanisms of nickel-induced toxicity. Primary oral keratinocytes and gingival fibroblasts were seeded onto Alloderm™ and maintained until full-thickness was achieved prior to Ni-Cr and cobalt-chromium (Co-Cr) alloy-disc exposure (2-72 h). Biocompatibility assessment involved histological analyses with cell viability measurements, oxidative stress responses, inflammatory cytokine expression and cellular toxicity analyses. Inductively coupled plasma mass spectrometry (ICP-MS) analysis determined elemental ion release levels. We detected adverse morphology with significant reductions in cell viability, significant increases in oxidative stress, inflammatory cytokine expression and cellular toxicity for the Ni-Cr alloy-treated oral mucosal models compared with untreated oral mucosal models and adverse effects were increased for the Ni-Cr alloy that leached the most nickel. Co-Cr demonstrated significantly enhanced biocompatibility compared with Ni-Cr alloy-treated oral mucosal models. The human-derived full-thickness oral mucosal model was discriminatory between dental alloys and mechanistically provided insights into Ni-induced toxicity, highlighting potential clinical relevance. Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/61625 Title: DIFFERENTIAL VIRULENCE OF CANDIDA ALBICANS AND CANDIDA DUBLINIENSIS: A ROLE FOR TOR KINASE? Author: SULLIVAN, DEREK; MORAN, GARY Abstract: Candida albicans and Candida dubliniensis are two very closely related species of pathogenic yeast. C. albicans is the most prevalent species in the human gastrointestinal tract and is responsible for far more opportunistic infections in comparison with C. dubliniensis. This disparity is likely to be due to the reduced ability of C. dubliniensis to undergo the yeast to hypha transition, a change in morphology that plays an important role in C. albicans virulence. We have recently shown that hypha formation by C. dubliniensis is specifically repressed by nutrients at alkaline pH. In this article, we present new data showing that this can be partly reversed by treatment with rapamycin, an inhibitor of the nutrient sensing kinase Tor1 (Target Of Rapamycin). We also provide a speculative model to describe why C. albicans filaments more efficiently in nutrient rich environments, citing recently described data on Mds3, a pH responsive regulator of Tor1 kinase activity. Description: PUBLISHED 2011-01-01T00:00:00Z http://hdl.handle.net/2262/61049 Title: MANAGEMENT OF DENTAL UNIT WATERLINE BIOFILMS IN THE TWENTY-FIRST CENTURY Author: RUSSELL, RONALD J; O'DONNELL, MARY J; COLEMAN, DAVID Abstract: Dental chair units (DCUs) use water to cool and irrigate DCU-supplied instruments and tooth surfaces and provide rinsewater during dental treatment. A complex network of interconnected plastic dental unit waterlines (DUWLs) supplies this water to these instruments. DUWLs are universally prone to microbial biofilm contamination seeded predominantly from microorganisms in supply water. Consequently, DUWL output water invariably becomes contaminated by high densities of microorganisms, principally Gram-negative environmental bacteria including Pseudomonas aeruginosa and Legionella species, but sometimes contains human-derived pathogens such as Staphylococcus aureus. Patients and staff are exposed to microorganisms from DUWL output water and to contaminated aerosols generated by DCU instruments. A wide variety of approaches, many unsuccessful, have been proposed to control DUWL biofilm. More recently, advances in biofilm science, chemical DUWL biofilm treatment agents, DCU design, supply water treatment and development of automated DUWL biofilm control systems have provided effective long-term solutions to DUWL biofilm control. Description: PUBLISHED 2011-01-01T00:00:00Z