Biomedical subjects

L P Samaranayake

Publications and source records attributed to L P Samaranayake.

At least 19 recordsLinked to original sources

PubMed2006

(B1) Candida and mycotic infections.

Oral candidiasis (OC) is the most common mucosal manifestation of HIV infection. This workshop examined OC and other mycoses associated with HIV infection. Historically, blood CD4 cell numbers were the primary prognosticator for the development of OC. However, a study that statistically evaluated the predictive role of HIV viral load vs. CD4 cell counts revealed viral load to be a stronger predictor for OC. The role of biofilms and antifungal resistance in recalcitrant OC is unclear at present. In general, micro-organisms including yeasts in biofilms are more resistant to antifungals than their planktonic counterparts. When the remaining organisms are eliminated, the few resistant organisms may not be problematic, because they are present in low numbers. Unusual exotic mycoses in HIV-infected patients are more common in patients from the developing than the developed world. These infections may be recurrent and recalcitrant to therapy, be present in multiple and uncommon sites, increase with the progression of HIV disease, and may play a role similar to that of the more common mycoses. Typing and subtyping of yeasts are probably not critical to the clinical management of candidiasis caused by Candida albicans and non-albicans strains, including C. dubliniensis, because it is responsive to antifungal therapy. C. glabrata is probably the only exception. The presence of oral thrush in infants younger than 6 months of age is associated with an increased post-natal transmission risk of HIV infection. Thus, perinatal retroviral therapy should be combined with the treatment of oral thrush to prevent the post-natal acquisition of HIV.

AIDS-Related Opportunistic Infections↗

PubMed2006

In vitro adhesion of Candida species to denture base materials.

Adhesion of Candida species to prosthetic acrylic resins is an essential first step in the pathogenesis of denture stomatitis. Data on the relative adhesion of pathogenic non-albicans Candida species to different denture base materials are sparse. The purpose of the present study was to investigate in vitro adhesion of C. albicans, C. glabrata, C. krusei and C. dubliniensis to four different denture base materials. Specimens of both heat-cured resins (Vertex(TM) Rapid Simplified and ProBase Hot) and cold-cured resins (Paladur A and Paladur B) were prepared using a novel method and the adhesion of four strains each of the foregoing Candida species evaluated microscopically using a soft imaging system. There was a significant difference in yeast adherence between Vertex and the other resins. Only C. glabrata attached to Vertex, while all the remainder of the tested species adhered to all other resins tested except ProBase, which resisted C. krusei adhesion. There was a significant difference in candidal adhesion between cold-cured and heat-cured resins for three Candida species (C. albicans, P = 0.039; C. glabrata, P = 0.002 and C. krusei, P = 0.000). The type of denture base material and whether they are heat-cured or cold-cured play an important role in modifying candidal adhesion.

Acrylic Resins↗

PubMed2006

Diabetes mellitus as a contributory factor in oral candidosis.

It has been reported that poor glycaemic control predisposes to oral candidal infection in diabetic patients. For instance, the carriage of Candida species and the density of candidal growth in the oral cavity is frequently claimed to be increased in patients with diabetes mellitus. However, the validity of these observations remains controversial. Hence, we review and discuss here the clinical data in the literature on the relationship between diabetes and oral candidal carriage and infection, and possible mechanisms associated with its pathogenicity.

Blood Glucose↗

PubMed2006

Interspecies variation in Candida biofilm formation studied using the Calgary biofilm device.

An in vitro assay to study multiple Candida biofilms, in parallel, has been carried out using the Calgary biofilm device (CBD). We here report: i) standardization of the CBD for Candida albicans biofilm formation, ii) kinetics of C. albicans biofilm formation, iii) biofilm formation by five Candida species, and iv) effect of dietary carbohydrates on biofilm formation. The biofilm metabolic activity on all CBD pegs was similar (p=0.6693) and C. albicans biofilm formation revealed slow growth up to 36 h and significantly higher growth up to 48 h (p<0.001). Significant differences in total biofilm metabolic activity were seen for glucose, fructose and lactose grown C. albicans compared with sucrose and maltose grown yeasts. Candida krusei developed the largest biofilm mass (p<0.05) relative to C. albicans, C. glabrata, C. dubliniensis and C. tropicalis. Scanning electron microscopy revealed that C. krusei produced a thick multilayered biofilm of pseudohyphal forms embedded within the polymer matrix, whereas C. albicans, C. dubliniensis and C. tropicalis biofilms consisted of clusters or chains of cells with sparse extracellular matrix material. We conclude that CBD is a useful, simple, low cost miniature device for parallel study of Candida biofilms and factors modulating this phenomenon.

Biofilms↗

PubMed2006

Differential phospholipase gene expression by Candida albicans in artificial media and cultured human oral epithelium.

Phospholipases B1, B2, C and D of Candida albicans play a significant role in the host invasive process. Hence we evaluated the in vitro expression of PLB1, PLB2, PLC1 and PLD1 in phospholipase-positive (PL(+)) and -deficient (PL(-)) C. albicans isolates in egg yolk agar (EYA), yeast peptone dextrose broth (YPD), and in a model of oral candidiasis based on reconstituted human oral epithelium (RHOE). The growth of Candida was then determined in YPD and its cellular invasion was investigated using the RHOE model. The PL(+) group demonstrated PLB1, PLB2, PLC1 and PLD1 expression in both EYA and YPD, in contrast to the PL(-) group, which expressed only PLB2 and PLD1. Although PL(+) isolates grew profusely in the RHOE model, they expressed only PLB2, PLC1 and PLD1, and not PLB1. Gene expression investigations could not be carried out with PL(-) isolates due to their inability to grow in the RHOE model. Significant growth differences in YPD medium were also observed within the PL(+) and PL(-) groups. Taken together, these findings indicate that phospholipase gene expression in C. albicans is differentially affected by their growth milieu, and this in turn may modulate the disease outcomes in vivo.

Candida albicans↗

PubMed2006

Quantitative evaluation of tissue invasion by wild type, hyphal and SAP mutants of Candida albicans, and non-albicans Candida species in reconstituted human oral epithelium.

BACKGROUND: Oral candidiasis is a common problem in compromised patients. Although several non-albicans Candida species have emerged as pathogens the majority of candidal infections are caused by Candida albicans. Morphogenesis from the blastospore to filamentous phase, and production of secretory aspartyl proteinases (SAP) are two major virulence attributes of these opportunistic yeast. Histopathology of oral candidiasis is characterized by fungal invasion of the superficial epithelium although the invasive potentials of different Candida species vary. Computerized image analysis systems (IAS) utilizing immunohistochemistry have been successfully employed for quantification of such histopathological features. The purpose of this study was to evaluate quantitatively the in vitro invasive potential of C. albicans and its hyphal and SAP mutants, and five other non-albicans Candida species using a computerized IAS. METHODS: In vitro human oral candidiasis was produced using five wild type and one reference C. albicans isolates, hyphal and SAP mutants of C. albicans SC 5314, and one wild type and one reference isolate each of C. tropicalis, C. dubliniensis, C. glabrata, C. parapsilosis and C. krusei in a reconstituted human oral epithelium (RHOE) model. The infected tissues were examined histologically at 12, 24 and 48 h. Invading fungal elements were visualized by periodic acid-Schiff (PAS) staining and quantitatively evaluated as a percentage of total tissue invasive area, using a computerized IAS. RESULTS: All C. albicans isolates including hyphal mutant cph1/cph1 and SAP mutants; sap 1-3, sap 4-6 produced hyphae and differentially (P < 0.05) invaded the tissue over 48 h. The invasive potential of hyphal mutant cph1/cph1 and SAP mutants (sap 1-3, sap 4-6) were similar to the parent wild-type isolate at 12 h although after 24 h their invasion was dissimilar (P < 0.05). Non-albicans Candida species and hyphal mutants; efg1/efg1, efg1/efg1 cph1/cph1 were all non-invasive. CONCLUSIONS: RHOE model in combination with computerized image analysis permits for the first time, the assessment of invasive potential of Candida species in a quantitative manner. The differential tissue invasive patterns of various C. albicans isolates, their mutants and other Candida species are also described.

Aspartic Acid Endopeptidases↗

PubMed2006

In vitro antifungal effect of amine fluoride-stannous fluoride combination on oral Candida species.

OBJECTIVE: The combination of amine fluoride and stannous fluoride (AmF/SnF2) was, by chance, found to be antifungal in a clinical trial. This study investigated its effect on pathogenic Candida species with the hypothesis that the antifungal action on different species is variable. MATERIALS AND METHODS: Growth inhibition effect of Meridol mouth rinse which contains 250 ppm AmF/SnF2 was evaluated on 43 reference and clinical strains of Candida albicans, C. dubliniensis, C. glabrata, C. guilliermondii, C. krusei, C. parapsilosis, and C. tropicalis. Meridol base solution without AmF/SnF2 was used as a negative control. RESULTS: Undiluted Meridolmouth rinse killed most study strains within a few minutes. In ascending order, C. parapsilosis, C. tropicalis, C. albicans, C. glabrata, C. krusei and C. dubliniensis showed higher resistance against AmF/SnF2 than C. guilliermondii. CONCLUSION: AmF/SnF2 could be used as a potent adjunct to antifungal therapy for oral yeasts. Although different Candida species demonstrated variable sensitivity the most prevalent oral yeast C. albicans appeared sensitive to the AmF/SnF2 combination.

Amines↗

PubMed2006

DNA fingerprinting elicited evolutionary trend of oral Candida tropicalis isolates from diverse geographic locales.

PURPOSE: To study molecular profiles of oral Candida tropicalis isolates from five different geographic locales to determine the molecular diversity, clonality and evolutionary trends of this opportunistic pathogen. METHODS: A total of 36 strains from five countries (China, Canada, Scotland, Japan and Tanzania) were genotyped by PCR fingerprinting with 11 separate primers. Of these, primers RSG9, RSG8, T3B and RSD12 generated complex fingerprinting patterns. RESULTS: Three significantly dissimilar profiles were derived from the primer T3B and particularly focused on tDNA suggested the prevalence of genetic subtypes within the species. Comparison of tDNA and rDNA (RSD12) fingerprints of C. tropicalis suggested that rDNA is much more heterogeneous than the relatively distinct tDNA. Further analysis of similarity coefficient (SAB) of gel profiles derived from computer-generated dendrograms indicated some degree of similarity in isolates from five-disparate geographic locales as well as the presence of unique isotypes in each region. CONCLUSIONS: This study demonstrates the evolutionary divergence of distinct genetic subgroups within Candida tropicalis .

AIDS-Related Opportunistic Infections↗

PubMed2005

The use of new probes and stains for improved assessment of cell viability and extracellular polymeric substances in Candida albicans biofilms.

Phenotypic and genotypic cell differentiation is considered an important feature that confers enhanced antifungal resistance in candidal biofilms. Particular emphasis has been placed in this context on the viability of biofilm subpopulations, and their heterogeneity with regard to the production of extracellular polymeric substances (EPS). We therefore assessed the utility of two different labeled lectins Erythrina cristagalli (ECA) and Canavalia ensiformis (ConA), for EPS visualization. To evaluate the viability of candidal biofilms, we further studied combination stains, SYTO9 and propidium iodide (PI). The latter combination has been successfully used to assess bacterial, but not fungal, viability although PI alone has been previously used to stain nuclei in fungal cells. Candida albicans biofilms were developed in a rotating disc biofilm reactor and observed in situ using confocal scanning laser microscopy (CSLM). Our data indicate that SYTO9 and PI are reliable vital stains that may be used to investigate C. albicans biofilms. When used together with ConA, the lectin ECA optimized EPS visualization and revealed differential production of this material in mature candidal biofilms. The foregoing probes and stains and the methodology described should help better characterize C. albicans biofilms in terms of cell their viability, and EPS production.

Biofilms↗

PubMed2005

Characterization of switch phenotypes in Candida albicans biofilms.

The aim of this study was to characterize switch phenotypes in Candida albicans biofilms. Cells of Candida albicans 192887g biofilms (24 h) were resuspended and these together with their planktonic counterparts were separately inoculated on Lee's medium agar supplemented with arginine and zinc, at 25 degrees C for 9 days, for colony formation. The different switch phenotypes, as reflected by varying colony morphologies, were then examined for their (i) stability under various growth conditions, (ii) carbohydrate assimilation profiles, (iii) susceptibility to the polyene antifungal, nystatin, (iv) adhering and biofilm-forming ability, (v) filamentation, and (vi) growth rate in yeast nitrogen base medium supplemented with 100 mM glucose. Our data showed that the frequency of phenotypic switching in C. albicans biofilms was approximately 1%. Compared with the planktonic yeasts, cells derived from candidal biofilms generated one of the phenotypes less frequently (Chi-square-tests: P = 0.017). The five phenotypes derived from the biofilm growth demonstrated differing profiles for carbohydrate assimilation, adhesion, biofilm formation, filamentation, and growth rate. These findings reported here, for the first time, imply that phenotypic switching in the candidal biofilms differs from that in the planktonic growth, and affects multiple biological attributes.

Biofilms↗

PubMed2005

Coaggregation profiles of the microflora from root surface caries lesions.

Bacterial coaggregation reactions between different species and the auto aggregation of the same species are associated with the initiation and development of dental plaque and biofilms. As no such data is available on isolates from root caries lesions, we evaluated, by a visual, semi-quantitative scoring system and a spectrophotometric, quantitative assay, the coaggregation of 22 different wild-type microbial species comprising ten bacterial genera and a single Candida spp. The quantitative coaggregation assay we used proved to be a more sensitive method than the semi-quantitative, visual evaluation as the results yielded the percent coaggregation. Fusobacterium nucleatum, Lactobacillus acidophilus, Streptococcus bovis II/2 and Gemella morbillorum were observed having higher degrees of autoaggregation than the other examined strains. Significant levels of inter-species coaggregation was seen between: (1) Actinomyces spp. and Veillonella spp.; (2) Actinomyces israelii and Peptostreptococcus prevotii; (3) Campylobacter gracilis and Actinomyces spp.; (4) Prevotella intermedia and nine different species; and (5) Fusobacterium nucleatum and six other species. The single Candida albicans isolate did not coaggregate to a significant extent with any of the 21 bacterial isolates studied. Scanning electron microscopy observation of the coaggregation interactions between bacterial pairs having strong coaggregation reactions revealed varying adhesive patterns. Our findings on coaggregation amongst these isolates imply existence of multiple interactions between the coaggregation-inducing bacterial species in root caries. In particular, Actinomyces spp., Veillonella spp., Prevotella spp. and Fusobacterium spp. appear to play a significant role in this context.

Aged↗

PubMed2005

Clindamycin in dentistry: more than just effective prophylaxis for endocarditis?

Clindamycin is a broad-spectrum antibiotic with activity against aerobic, anaerobic, and beta-lactamase-producing pathogens. This antibiotic has been used for many years as prophylactic treatment during dental procedures to prevent endocarditis. However, the spectrum and susceptibility of the bacteria species involved in dental infections indicate that clindamycin would also be an effective treatment option for these conditions. In addition to its antiinfective properties, clindamycin has high oral absorption, significant tissue penetration, including penetration into bone, and stimulatory effects on the host immune system. This review discusses the microbiologic and clinical evidence supporting the efficacy and safety of clindamycin for the successful management of dental infections.

Anti-Bacterial Agents↗

PubMed2005

Phospholipase B enzyme expression is not associated with other virulence attributes in Candida albicans isolates from patients with human immunodeficiency virus infection.

The extracellular phospholipases of Candida albicans are considered to play a significant role in the pathogenesis of human infections. Therefore 30 clinical isolates of C. albicans from human immunodeficiency virus (HIV)-infected individuals were screened for phospholipase production in vitro (using an egg-yolk-agar medium). Two groups of six isolates with positive (group A) or deficient (group B) phospholipase activity were then analysed for phospholipase B1 (PLB1) gene expression both in egg-yolk-agar and yeast extract/peptone/dextrose (YPD) broth media. A total of four virulence attributes of these two groups were in turn characterized, namely their germ-tube formation, cell-surface-hydrophobicity (CSH), adhesion to buccal epithelial cells (ABEC) and haemolysin production, and these factors were subsequently correlated with PLB1 expression. In the phospholipase-producing isolates (group A) a positive correlation was demonstrated between phospholipase production and the degree of PLB1 expression in YPD medium (r = 0.96, P < 0.01). No such association was observed in group A isolates for PLB1 expression in egg-yolk-agar medium. Further, PLB1 expression in egg-yolk agar was less than that in YPD medium, although a positive correlation was seen between the expression levels on regression analysis (r = 0.86, P = 0.026). Surprisingly, however, no significant associations were observed in either growth media between PLB1 expression and any of the four pathogenic attributes examined (P < 0.001). A significant correlation was seen between CSH and ABEC (r = 0.74) in group A isolates. The phospholipase-deficient group B, however, demonstrated a significant correlation between the latter parameters (r = +0.50) and also between germ-tube formation and ABEC (r = -0.59), and germ-tube formation and haemolysin production (r = +0.31). It appears that in oral C. albicans isolates in HIV infection there may be no significant association between the degree of PLB1 expression and other widely recognized major virulence attributes.

Bacterial Adhesion↗

PubMed2005

Oral Candida species and betel quid-associated oral lesions in Padaung women of Northern Thailand.

Purpose of the present investigation was to study the association between the betel quid chewing (BQC) habits, the oral yeast flora and oral lesions in female Padaung of northern Thailand. Oral swabs were taken from the tongue and palate of 50 Padaung women with and 50 control individuals without BQC habit. The spectrum of oral Candida species in both groups was determined microbiologically. In addition, oral mucosal lesions were registered in both groups. Mean age of BQ chewers was 35.4 years, of non-chewers was 19.2 years. Candida parapsilosis was the most common Candida spp. isolated both in BQ chewers (46%) and non-chewers (44%). Candida albicans was revealed in 24% of BQ chewers and 18% of non-chewers. There was no significant difference in carriage of Candida spp. isolated between both groups. Forty-four per cent of BQ chewers revealed betel chewers mucosa, 10% showed leukoedema. Isolated populations such as the Padaung may reveal different patterns of candidal flora, in this case a predominance of Candida parapsilosis.

Adolescent↗

PubMed2005

An ultrastructural and a cytochemical study of candidal invasion of reconstituted human oral epithelium.

BACKGROUND: Opportunistic yeast, Candida albicans causes superficial and systemic mycoses in compromised patients. Adhesion to host tissues, morphogenesis and extracellular phospholipases (PL) are thought to contribute to its virulence. The nature of numerous host-parasite interactions at the invasive phase of oral candidiasis is not fully understood. Hence in this study, we explore the ultrastructural features of oral candidiasis using a tissue culture model based on reconstituted human oral epithelium (RHOE). METHODS: Reconstituted human oral epithelium (Skinethic Laboratory, Nice, France) was inoculated with C. albicans SC5314 and incubated up to 48 h. The infected tissue was harvested at 12, 24 and 48 h and examined using light, scanning (SEM) and transmission electron microscopy (TEM). Localized activity of PLs of C. albicans during tissue invasion was also examined using a cytochemical method. RESULTS: Over a period of 48 h C. albicans invaded the RHOE, and histological examination revealed characteristic hallmarks of pathological tissue invasion. Hyphal penetration into the superficial epithelium, particularly at cell junctions, together with features of cellular internalization of yeasts was noted. Phospholipase activity was visible at the tips of hyphae and initial sites of bud formation. Further, SEM studies revealed cavitations on the surface epithelial cells particularly pronounced at the sites of hyphal invasion. Hyphal invasion was seen both at cell surfaces and intercellular cell junctions of the epithelium, the latter resembling thigmotropic behaviour. CONCLUSIONS: Our findings confirm that multiple cellular interactions such as internalization, thigmotropism and extracellular PLs contribute to invasive candidiasis. The RHOE model, described here, appears to be a satisfactory model for the investigation of ultrastructural and histochemical features of invasive candidiasis in humans.

Candida↗

PubMed2005

In vitro method to study antifungal perfusion in Candida biofilms.

Antimycotic perfusion through Candida biofilms was demonstrated by a modification of a simple in vitro diffusion cell bioassay system. Using this model, the perfusion of three commonly used antifungal agents, amphotericin B, fluconazole, and flucytosine, was investigated in biofilms of three different Candida species (i.e., Candida albicans, Candida parapsilosis, and Candida krusei) that were developed on microporous filters. Scanning electron microscopy revealed that C. albicans formed a contiguous biofilm with tightly packed blastospores and occasional hyphae compared with C. parapsilosis and C. krusei, which developed confluent biofilms displaying structural heterogeneity and a lesser cell density, after 48 h of incubation on nutrient agar. Minor structural changes were also perceptible on the superficial layers of the biofilm after antifungal perfusion. The transport of antifungals to the distal biofilm-substratum interface was most impeded by C. albicans biofilms in comparison to C. parapsilosis and C. krusei. Fluconazole and flucytosine demonstrated similar levels of perfusion, while amphotericin B was the least penetrant through all three biofilms, although the latter appeared to cause the most structural damage to the superficial cells of the biofilm compared with the other antifungals. These results suggest that the antifungal perfusion through biofilm mode of growth in Candida is dependent both on the antimycotic and the Candida species in question, and in clinical terms, these phenomena could contribute to the failure of Candida biofilm-associated infections. Finally, the in vitro model we have described should serve as a useful system to investigate the complex interactions that appear to operate in vivo within the biofilm-antifungal interphase.

Amphotericin B↗

PubMed2004

Severe acute respiratory syndrome (SARS) and the GDP. Part II: implications for GDPs.

The transmission modes of SARS-coronavirus appear to be through droplet spread, close contact and fomites although air borne transmission has not been ruled out. This clearly places dental personnel at risks as they work in close proximity to their patients employing droplet and aerosol generating procedures. Although the principle of universal precautions is widely advocated and followed throughout the dental community, additional precautionary measures - termed standard precaution may be necessary to help control the spread of this highly contagious disease. Patient assessment should include questions on recent travel to SARS infected areas and, contacts of patients, fever and symptoms of respiratory infections. Special management protocols and modified measures that regulate droplet and aerosol contamination in a dental setting have to be introduced and may include the reduction or avoidance of droplet/aerosol generation, the disinfection of the treatment field, application of rubber dam, pre-procedural antiseptic mouthrinse and the dilution and efficient removal of contaminated ambient air. The gag, cough or vomiting reflexes that lead to the generation of aerosols should also be prevented.

Aerosols↗

PubMed2004

Severe Acute Respiratory Syndrome (SARS) and the GDP. Part I : Epidemiology, virology, pathology and general health issues.

The health profession faces a new challenge with the emergence of a novel viral disease Severe Acute Respiratory Syndrome (SARS), a form of atypical pneumonia caused by a coronavirus termed SARS-CoV. This highly infectious disease has spread through 32 countries, infecting more than 8,400 patients with over 790 deaths in just over 6 months. Over one quarter of those infected were unsuspecting healthcare workers. The major transmission mode of SARS-coronavirus appears to be through droplet spread with other minor subsidiary modes of transmission such as close contact and fomites although air borne transmission has not been ruled out. There is as yet no definitive treatment protocol. Although the peak period of the outbreak is likely to have passed and the risk of SARS in the UK is therefore assessed to be low, the World Health Organisation has asked all countries to remain vigilant lest SARS re-emerges. Recent laboratory acquired cases of SARS reported from Taiwan and Beijing, China are a testimony to this risk. Until reliable diagnostic tests, vaccine and medications are available, control of SARS outbreaks depends on close surveillance, early identification of index cases, quick isolation of carriers and effective infection control and public health measures.

China↗