Common benign and malignant oral mucosal disease.

BACKGROUND: Mucosal diseases of the oral cavity are relatively common, and patients often seek initial assessment from their general practitioner. OBJECTIVE: The aim of this article is to provide an overview of common oral mucosal diseases to help with formulating a differential diagnosis and stratifying the urgency of referral. DISCUSSION: Pathological mucosal conditions of the oral cavity and jaws commonly present as a mucosal ulcer or a white, red or pigmented lesion. In this review, the authors outline the most common conditions organised according to their clinical presentation and describe their typical appearance and management.

Elucidating the role of hyposalivation and autoimmunity in oral candidiasis.

INTRODUCTION: Oral candidiasis (OC) is a potential oral complication in Sjögren's syndrome (SS). Some studies indicate that the low stimulated salivary flow and not low unstimulated salivary flow is associated with OC in SS, while others report that the underlying autoimmune disorders contribute to OC, based solely on correlation coefficients. Given the conflicting and limited existing evidence, we purposed to ascertain the role of both salivary gland dysfunction (hyposalivation based on unstimulated and stimulated flow rates) and autoimmunity (SS, other autoimmune disorders) in OC among those with SS, other salivary gland dysfunction, and non-salivary gland dysfunction controls (NSGD). METHODS: A nested case-control study was designed within a larger NIH/NIDCR cohort. Descriptive analyses, nonparametric tests, comparative analyses, and multivariate logistic regression analyses were undertaken. RESULTS: Data on 1526 subjects (701 SS, 247 ISS, 355 Sicca, and 223 NSGD) were obtained from the source cohort of 2046 and analyzed for this study. The median whole unstimulated salivary flow rate (WUS, ml 15 min-1 ) was lower in SS (0.8, interquartile range (IQR) 1.8) compared to ISS (5.5, IQR: 5.2, P < 0.001) and NSGD (3.8, IQR: 3.8, P < 0.001) but comparable with that of Sicca (1.0, IQR: 1.5, P = 0.777) participants. The median total stimulated salivary flow rate (TSS, ml 15 min-1 ) was lowest in SS (7.0, IQR: 12.4, P < 0.001) compared to other groups. Of the 45 OC cases in this cohort, 71.1% (n = 32) were from the SS group. The prevalence of OC was highest in the SS group (4.6%, P = 0.008). SS group had twice the risk of OC than NSGD (OR = 2.2, 95%CI: 1.1-4.2, P = 0.02) and Sicca (OR = 2.2, 95% CI: 1.0-4.8, P = 0.03), adjusting for confounders; hyposalivation [WUS (OR = 5.1, 95%CI: 2.5-10.4, P < 0.001), TSS (OR = 1.9, 95%CI: 1.0-3.5, P = 0.04)], history of other autoimmune disorders (OR = 4.4, 95%CI: 1.7-11.3, P = 0.002), medications for extraglandular manifestations (OR = 2.3, 95%CI: 1.1-4.9, P = 0.03), and diabetes mellitus (4.2, 95%CI: 1.2-15.2, P = 0.02) were independent predictors of OC; females had a lower risk than males (OR = 0.29, 95%CI: 0.13-0.67, P = 0.004). Age, race, anti-SSA/SSB autoantibodies, focus score, other medications, anxiety, fatigue, cigarette smoking, alcohol, and caffeine use were not associated with oral candidiasis. CONCLUSION: Salivary gland dysfunction (hyposalivation with WUS being a stronger predictor than TSS) and autoimmunity (SS, other autoimmune disorders, medications, i.e., DMARDS) are both independent predictors of OC. Diabetes mellitus is an independent predictor of OC among those with salivary gland dysfunction. Our findings suggest that these independent predictors should be considered in the prevention and management of OC in this population.

[Oral ecosystem in elderly people]. / L'écosystème buccal chez le patient âgé

The mouth is a complex natural cavity which constitutes the initial segment of the digestive tract. It is an essential actor of the vital functions as nutrition, language, communication. The whole mouth (teeth, periodontium, mucous membranes, tongue) is constantly hydrated and lubricated by the saliva. At any age, a balance becomes established between the bacterial proliferations, the salivary flow, the adapted tissular answer: it is the oral ecosystem. The regulation of this ecosystem participates in the protection of the oral complex against current inflammatory and infectious pathologies (caries, gingivitis, periodontitis, candidiasis). In elderly, the modification of the salivary flow, the appearance of specific pathologies (root caries, edentulism, periodontitis), the local conditions (removable dentures), the development of general pathologies, the development of general pathologies (diabetes, hypertension, immunosuppression, the insufficient oral care are so many elements which are going to destabilize the oral ecosystem, to favor the formation of the dental plaque and to weaken oral tissues. The preservation of this ecosystem is essential for elderly: it allows to eat in good conditions and so to prevent the risks of undernutrition. The authors describe the oral physiopathology (oral microflora, salivary secretion) and the strategies to be adopted to protect the balance of the oral ecosystem in geriatric population.

Effects of salivary protein flow and indigenous microorganisms on initial colonization of Candida albicans in an in vivo model.

BACKGROUND: Candida albicans is a dimorphic fungus that is part of the commensal microbial flora of the oral cavity. When the host immune defenses are impaired or when the normal microbial flora is disturbed, C. albicans triggers recurrent infections of the oral mucosa and tongue. Recently, we produced NOD/SCID.e2f1-/- mice that show hyposalivation, decrease of salivary protein flow, lack IgA and IgG in saliva, and have decreased NK cells. Our objective was to characterize C. albicans infection and biofilm formation in mice. METHODS: NOD/SCID.e2f1-/- mice were used as an animal model for C. albicans infection. C. albicans yeast and hyphal forms solutions were introduced in the oral cavity after disinfection by Chlorhexidine. RESULTS: The numbers of C. albicans colonized and decreased in a time-dependent manner in NOD/SCID.e2f1+/+ after inoculation. However, the colonization levels were higher in NOD/SCID.e2f1+/+ than NOD/SCID.e2f1-/- mice. In the mice fed 1% sucrose water before inoculation, C. albicans sample was highly contaminated by indigenous microorganisms in the oral cavity; and was not in the mice fed no sucrose water. The colonization of C. albicans was not influenced by the contamination of indigenous microorganisms. The hyphal form of C. albicans restricted the restoration of indigenous microorganisms. The decreased saliva in NOD/SCID.e2f1-/- did not increase the colonization of C. albicans in comparison to NOD/SCID.e2f1+/+ mice. We suggest that the receptor in saliva to C. albicans may not be sufficiently provided in the oral cavity of NOD/SCID.e2f1-/- mice. CONCLUSION: The saliva protein flow may be very important for C. albicans initial colonization, where the indigenous microorganisms do not affect colonization in the oral cavity.

Candida albicans-epithelial interactions: dissecting the roles of active penetration, induced endocytosis and host factors on the infection process.

Candida albicans frequently causes superficial infections by invading and damaging epithelial cells, but may also cause systemic infections by penetrating through epithelial barriers. C. albicans is a remarkable pathogen because it can invade epithelial cells via two distinct mechanisms: induced endocytosis, analogous to facultative intracellular enteropathogenic bacteria, and active penetration, similar to plant pathogenic fungi. Here we investigated the contributions of the two invasion routes of C. albicans to epithelial invasion. Using selective cellular inhibition approaches and differential fluorescence microscopy, we demonstrate that induced endocytosis contributes considerably to the early time points of invasion, while active penetration represents the dominant epithelial invasion route. Although induced endocytosis depends mainly on Als3-E-cadherin interactions, we observed E-cadherin independent induced endocytosis. Finally, we provide evidence of a protective role for serum factors in oral infection: human serum strongly inhibited C. albicans adhesion to, invasion and damage of oral epithelial cells.

[Mycological examination and the taste disorder test for the tongues of diabetes mellitus patients].

The mycological examination by the cotton swab method and the taste disorder test using the filter-paper method were taken for the tongues of diabetes mellitus (DM) patients. Candida albicans was isolated from 29 out of 81 patients. The mean serum HbA1c level of patients with C. albicans was significantly higher than that of patients without it. DM patients demonstrated significantly higher incidences of taste disorders than healthy controls, but there was no relationship between C. albicans of the tongue and taste disorders. The taste disorders tended to occur in the DM patients who had nerve complications. The results suggested the taste disorder test using the filter-paper methods contributes to easy detection of the nerve complications in DM patients.

Oral candidosis in HIV-infected patients.

Oral candidosis (syn. Oral candidiasis; OC), is a collective term given to a group of oral mucosal disorders caused by the fugal pathogen belonging to the genus Candida. The association of OC with the human immunodeficiency virus (HIV) infection has been known since the advent of the acquired immune deficiency syndrome (AIDS) pandemic. OC is one of the earliest manifestations of HIV disease in high risk individuals not undergoing chemotherapy and is also a strong predictor of the subsequent risk of AIDS-related illness or death. With the advances in HIV therapy, such as highly active anti-retroviral therapy (HAART), the prevalence and presenting features of OC have changed in HIV-infected individuals, especially those in industrialized countries. The presence of OC in "controlled" HIV-positive individuals may be indicative of a patient nonadherence to therapy or possible failure. The factors contributing to the genesis of OC and its progression in these individuals are poorly understood, but may include an interrelationship between HIV and Candida and/or a dysfunction in the local immunity, superimposed on weakened cell-mediated immunity and depletion of CD4 T cells. The dramatic increase in publications on this topic matches the increased importance and awareness of this opportunistic infection in HIV-infected individuals. In this review we first address the epidemiologic and clinical features of OC in HIV-infected persons, followed by the current understanding of the pathogenesis of OC in the context of HIV infection with a concluding section on the current management concepts of OC.

Cellular and molecular mechanisms of resistance to oral Candida albicans infections.

Oral candidiasis is a significant health problem in terms of both morbidity and economic outlay. Infections are predominantly caused by the commensal C. albicans, and affect immunocompromised individuals, including HIV-positive and AIDS patients, organ transplant recipients and chemotherapy patients. The molecular and cellular immune mechanisms involved in protection from and responses to oral candidiasis are overlapping, but distinct from those associated with other manifestations of the disease, including systemic, vaginal and gastric candidiasis. In oral candidiasis, clinical observations and experimental mouse models suggest a critical role for cell-mediated immunity. In mice, CD4+ T-cells and the p40 subunit of interleukins 12 and 23 are strict prerequisites for resistance; however abrogation of IFN-gamma does not confer susceptibility. Here, we discuss this apparent inconsistency, and review the experimental evidence that clarifies which immune pathways are specifically involved in resistance and responses to candidiasis of the oral cavity. We also highlight deficiencies in the literature, particularly concerning the putative roles of some relatively new elements in immunobiology: interleukin-23, interleukin-17 and T helper (Th)17 cells.

Characteristics of dual species Candida biofilms on denture acrylic surfaces.

UNLABELLED: Biofilms contribute to the pathogenesis of oral candidiasis, some 15% of which may be due to dual Candida species. Despite extensive studies on monospecies biofilms (MSB) on denture acrylic surfaces, few have investigated the characteristics of dual species Candida biofilms (DSB). OBJECTIVES: To examine interactions of DSB of Candida albicans and Candida krusei on denture acrylic surfaces. METHODS: Two isolates each of C. albicans (Ca) and C. krusei (Ck), with high (Ca(h), Ck(h)) and low (Ca(l), Ck(l)) biofilm-forming ability were used. The biofilms were developed on acrylic surfaces aerobically at 37 degrees C in yeast nitrogen base (YNB) medium, and growth quantified by colony-forming unit (CFU) assay. We determined: (i) the population profiles of DSB comprising each pair of Candida species, of a total of four combination pairs, after 12 h, (ii) the effect of a constant concentration of Ca(h) (10(7)cells/ml) on varying concentrations of Ck(h) (10(3)-10(7)cells/ml) on DSB development and (iii) the effect of saliva on the growth of DSB. RESULTS: (i) DSB exhibited a lower cell population after 9 or 12 h in comparison to MSB (P<0.05), (ii) C. albicans (10(7)cells/ml) co-cultured with varying initial concentrations of C. krusei was inhibited at high concentrations of the latter (10(6)-10(7)cells/ml) (P<0.05) and (iii) only the MSB development of C. krusei was affected by saliva (P<0.05). CONCLUSION: Our data suggest that the competitive interactions of fungal species are likely to be important in biofilm formation on acrylic surfaces and human saliva may further modulate this process.

Lesiones bucales en niños VIH/Sida y su relación con linfocitos CD4 y carga viral: Valencia / Mouth injuries in children with HIV/AIDS and their relation with CD4 limphocytes and viral load

El 90 por ciento de los pacientes VIH-SIDA presentan lesiones bucales durante el curso de la enfermedad, observándose en la mayoría de los niños en las etapas iniciales, lesiones muchas veces no imputables al VIH. Determinar las manifestaciones bucales y su relación con el porcentaje de linfocitos CD4 y la carga viral, en 40 niños VIH/SIDA que acudieron a la consulta de infectología y odontología pediátrica de la Ciudad Hospitalaria “Dr. Enrique Tejera”. A través de un estudio descriptivo y de campo, se analizaron las variables, edad, género, categoría clínico-inmunológica, manifestaciones en tejidos blandos y duros, porcentaje de linfocitos CD4 y carga viral. El grupo de niños más afectado fue el de 1 a 6 años y el género femenino. La categoría clínica inmunológica más frecuente fue la B2 y la C3. En 65 por ciento hubo caries y en 80 por ciento lesión de tejidos blandos. La lesión bucal más común fue: adenopatías 57.5 por ciento, seguida de candidiasis 30 por ciento, y en igual proporción (17,5 por ciento) afta-úlceras y gingivitis; parotiditis y xerostomía 12.5 por ciento, herpes oral y petequias 10 por ciento, queilitis 7.5 por ciento, leucoplasia vellosa y eritema gingival lineal 2.5 por ciento. Independientemente del porcentaje de CD4 y carga viral, se evidenciaron manifestaciones bucales en tejidos duros y blandos, en una frecuencia relativamente alta, de allí la imperiosa necesidad de institucionalizar los programas de atención odontológica, así como la instrucción, sensibilización y motivación a los padres, representantes y personal de salud en el área pediátrica, sobre la importancia de la salud bucal en los niños VIH/SIDA.

90 percent of the childrens infected with VIH-AIDS may be at increased risk of experiencing oral lesions during the course of the illness, principally at the initial stage, the most of these lesions were not associated to HIV. To determine the oral manifestations and their relation with the percentage of lymphocytes CD4 and the viral load, in 40 children being treated for HIV-infection of the Paediatric Infection and Dentistry Service at the “Ciudad Hospitalaria Dr. Enrique Tejera.”. By means of a descriptive study of field, the variables age, gender, immunological clinical category, soft and hard tissue manifestations, percentage of lymphocytes CD4, and viral load were analyzed. The childrens more affected were the group of 1 to 6 years old and in feminine gender. The most frequent immunological clinical category was the B2 and the C3. In 65 percent there was dental caries, and in 80 percent soft oral lesion. The most common oral manifestation was adenopaty 57,5 percent, followed of candidacies 30 percent, and in equal proportion 17.5 percent aphthous ulcerations, and gingival erythema, parotid en largement and xerostomia 12,5 percent, herpes oral and petechiae 10 percent, cheilitis 7,5 percent, hairy leukoplakia and gingival erythema linear 2.5 percent. Independently of percentage CD4 and the viral load, oral manifestations on hard tissue were recorded as much as in soft tissue. The hard and soft weave injuries were relatively high, consequently, the urgent necessity to institutionalize preventive and therapeutic dental program, and also the education, sensibilization and motivation to parents, representatives and health personnel in the paediatric area; about the importance of oral health in HIV/AIDS children.

Murine model of concurrent oral and vaginal Candida albicans colonization to study epithelial host-pathogen interactions.

We report the creation of a new low-estrogen murine model of concurrent oral and vaginal C. albicans colonization that resembles human candidal carriage at both mucosal sites. Weekly estrogen administration of 5 microg intramuscular and subcutaneously was optimal for enhancement of oral colonization and was essential for vaginal colonization. In BALB/c mice, a number of C. albicans clinical isolates (n=3) colonized both oral and/or vaginal sites, but only strain 529L colonized 100% of mice persistently for over 5 weeks. Laboratory strains SC5314 and NCPF 3153 did not colonize the model; however, NCPF 3156 showed vaginal colonization up to week 5. Prior passaging through mice enhanced subsequent colonization of SC5314. Intranasal immunization with a C. albicans virulence antigen (secreted aspartyl proteinase 2) significantly reduced or abolished the fungal burden orally and vaginally by week 2 and 7. Our concurrent model of mucosal colonization reduces the numbers of experimental mice by half, can be used to assess potential vaccine candidates, and permits the detailed analysis of host-fungal interactions during the natural state of Candida colonization.

Mucosal tissue invasion by Candida albicans is associated with E-cadherin degradation, mediated by transcription factor Rim101p and protease Sap5p.

The ability of Candida albicans to invade mucosal tissues is a major virulence determinant of this organism; however, the mechanism of invasion is not understood in detail. Proteolytic breakdown of E-cadherin, the major protein in epithelial cell junctions, has been proposed as a mechanism of invasion of certain bacteria in the oral mucosa. The objectives of this study were (i) to assess whether C. albicans degrades E-cadherin expressed by oral epithelial cells in vitro; (ii) to compare the abilities of strains with different invasive potentials to degrade this protein; and (iii) to investigate fungal virulence factors responsible for E-cadherin degradation. We found that while E-cadherin gene expression was not altered, E-cadherin was proteolytically degraded during the interaction of oral epithelial cells with C. albicans. Moreover, C. albicans-mediated degradation of E-cadherin was completely inhibited in the presence of protease inhibitors. Using a three-dimensional model of the human oral mucosa, we found that E-cadherin was degraded in localized areas of tissue invasion by C. albicans. An invasion-deficient rim101-/rim101- strain was deficient in degradation of E-cadherin, and this finding suggested that proteases may depend on Rim101p for expression. Indeed, reverse transcription-PCR data indicated that expression of the SAP4, SAP5, and SAP6 genes is severely reduced in the rim101-/rim101- mutant. These SAP genes are functional Rim101p targets, because engineered expression of SAP5 in the rim101-/rim101- strain restored E-cadherin degradation and invasion in the mucosal model. Our data support the hypothesis that there is a mechanism by which C. albicans invades mucosal tissues by promoting the proteolytic degradation of E-cadherin in epithelial adherens junctions.

Use of prophylactic antifungals in the immunocompromised host.

Oral candidiasis is a significant infection in patients being treated with chemotherapy and radiotherapy for cancer, and in patients who are immunocompromised because of HIV infection and AIDS. Candida albicans is the most common fungal pathogen and has developed an extensive array of putative virulent mechanisms that allows successful colonization and infection of the host under suitable predisposing conditions. The purpose of this review of the literature was to assess the effectiveness of interventions for the prevention of oral candidiasis in immunocompromised patients and in patients treated for cancer with radiotherapy and/or chemotherapy. These patient categories were selected because they have been the topic of published randomized controlled clinical trials. The studies reviewed provide strong evidence that oral candidiasis is associated with greater morbidity and mortality in these populations, which substantiates the aggressive treatment and prophylaxis of this infection. The literature supports the recommendation that systemically applied antifungal drugs have the greatest efficacy for the treatment of oral candidiasis in cancer and immunocompromised patients; however, these therapies must be prescribed with a thorough assessment for the risk for developing drug-induced toxicities. Guidelines on the prevention of drug-resistant oral candidiasis in these patients are not available and require elucidation. Further studies are required to expand the knowledge base of evidence-based antifungal therapies in a wider variety of immunocompromised patients and conditions, such as Sjögren's syndrome, diabetes, and denture wearers. Additional exploration is needed to determine which antifungal drug formulation, dose, and method of delivery is preferable for the type of fungal infection and the underlying etiology.

Hyphal invasion of Candida albicans inhibits the expression of human beta-defensins in experimental oral candidiasis.

Oral epithelium reacts to microbial challenges by eliciting a defensive response that includes the production of antimicrobial peptides. This study investigated the expression of human beta-defensins-1, 2, and 3 in reconstituted human oral epithelia during experimental oral infections with six different Candida species, and a wild-type C. albicans isolate and five of its mutants. The expression of defensins was induced after 12 hours infection with the wild-type C. albicans, but this response was not seen for the noninvasive hyphal mutants nor the secreted aspartyl proteinase mutants. Furthermore, defensin expression was not detected after 48 hours in epithelia infected with either C. albicans wild-type isolate or its invasive hyphal and proteinase mutants. Most of the non-albicans Candida were capable of inducing the expression of defensins in epithelia after 24 or 48 hours of infection. These Candida-host interaction patterns suggest that the oral epithelia possess mechanisms for sensing the early invasion of C. albicans through recognition of the presence of hyphae and proteinases of Candida and respond to the insult by producing antimicrobial peptides. This hyphal-invasion-dependent inhibition of defensin expression in oral epithelium that undermines the host surveillance system represents a hitherto undescribed novel pathogenic mechanism of C. albicans.

[Saliva substitutes]. / Les substituts salivaires.

Patients suffering from xerostomia lack oral comfort which reduces their ability to take up food properly and impairs their speech. Furthermore they suffer easily from caries and oral yeast infections. If it is impossible to stimulate a minimal salivary gland activity, salivary substitutes can be prescribed. Unfortunately, not all functions of saliva can be replaced by artificial products satisfactorily. Artificial saliva lacks a satisfactory efficacy with regards to lubrication, antimicrobial action and protection against demineralization. This can explain why these products are not widely known and their demand is very low. The optimal saliva substitute is not yet found.

Candida albicans IRS4 contributes to hyphal formation and virulence after the initial stages of disseminated candidiasis.

Candida albicans is a common cause of mucosal and bloodstream infections. As a screening strategy to identify novel candidal virulence factors, sera recovered from HIV-infected patients with active oropharyngeal candidiasis (OPC) were previously used to probe a C. albicans genomic expression library. IRS4 was identified as a gene that encodes an immunogenic protein. In the present study, the presence of IRS4 transcripts was verified within OPC pseudomembranes recovered from patients. Having confirmed that the gene is expressed during human candidiasis, gene disruption strains were created and this implicated IRS4 in diverse processes, including hyphal formation on solid media and under embedded conditions, cell wall integrity and structure, and adherence to human epithelial cells in vitro. IRS4 disruption, however, did not influence hyphal formation or virulence in a murine model of OPC. Rather, the gene was found to be necessary for normal morphogenesis and full virulence during murine intravenously disseminated candidiasis (DC). IRS4's effects on hyphal formation and virulence during DC were not evident on the first day after intravenous inoculation, even though transcripts were detected within murine kidneys. After 4 days, however, an irs4 null mutant strain was associated with attenuated mortality, diminished tissue burdens, less extensive infections, impaired C. albicans hyphal formation and decreased kidney damage. Taken together, these findings suggest that IRS4 makes distinct temporal-spatial contributions to the pathogenesis of candidiasis, which appear to vary between different tissue sites as well as within a given tissue over time.

Produção de biofilme por leveduras isoladas de cavidade bucal de usuários de prótese dentária / Biofilm production by yeasts isolated from bucal cavity of prosthesis wearers

Foi analisada a presença de espécies do gênero Candida na saliva de indivíduos distribuídos em três grupos: 1) com prótese e lesão; 2) com prótese sem lesão; 3) sem prótese e sem lesão, correlacionando com a capacidade de produção de biofilme em meio Sabouraud dextrose, contendo 8 por cento de glicose, sendo determinada por leitura em espectrofotômetro. Dos 220 pacientes foram isoladas 92 leveduras: 24 (grupo 1), 24 (grupo 2) e 44 (grupo 3). Em 70 por cento foi isolado C. albicans e 30 por cento C. não albicans. A produção de biofilme em maior freqüência (64 por cento) foi encontrada entre as leveduras C. não albicans e a maior porcentagem na produção de biofilme, quanto aos grupos de pacientes, foram 75, 63 e 57 por cento correspondendo aos grupos 1, 2 e 3, respectivamente. Esses dados sugerem que a produção de biofilme das espécies do gênero Candida pode estar associada ao processo infeccioso destes isolados

Role of the fungal Ras-protein kinase A pathway in governing epithelial cell interactions during oropharyngeal candidiasis.

Tpk1p, Tpk2p and Efg1p are members of the Ras-protein kinase A pathway that governs the yeast-to-hyphal transition in Candida albicans. We used tpk1Delta/tpk1Delta, tpk2Delta/tpk2Delta and efg1Delta/efg1Delta mutants to investigate the role of these proteins in regulating the interactions of C. albicans with oral epithelial cell lines in vitro and virulence in murine models of oropharyngeal candidiasis (OPC) and haematogenously disseminated candidiasis (HDC). The tpk1Delta/tpk1Delta strain adhered to, invaded and damaged oral epithelial cells in vitro similarly to the wild-type strain. In contrast, both the tpk2Delta/tpk2Delta and efg1Delta/efg1Delta strains had reduced capacity to invade and damage oral epithelial cells, and the efg1Delta/efg1Delta strain also exhibited decreased adherence to these cells. Consistent with these in vitro findings, the tpk2Delta/tpk2Delta and efg1Delta/efg1Delta strains also had significantly attenuated virulence during OPC. Therefore, Tpk2p and Efg1p both govern factors that enable C. albicans to invade and damage oral epithelial cells in vitro and cause OPC. These results also suggest that hyphal formation mediated by the Ras-protein kinase A pathway is a key virulence mechanism during OPC. Interestingly, the efg1Delta/efg1Delta strain, but not the tpk2Delta/tpk2Delta had reduced virulence during HDC. Thus, Tpk2p may be more important for governing virulence during OPC than HDC.

Electrophoretic variants of intracellular catalase of different Candida species.

Intracellular and extracellular catalases of different species of Candida were investigated using different culture media. All the Candida strains produced intracellular catalase, whose enzymatic activity was detected by non-denaturating polyacrylamide gradient (4-30%) gel electrophoresis. The cell extracts presented a major 230 kDa catalase band and in some strains variants of catalase with different molecular weights were detected. Candida catalase activity was not affected by heating at 50 degrees C and incubation with beta-mercaptoethanol, but treatment with sodium dodecyl sulphate inhibited or reduced enzymatic activity. Extracellular enzyme activity was not detected in any of the culture filtrate extracts tested.