Invasion process ofCandida albicansto tongue surface in early stages of experimental murine oral candidiasis

Saccharomyces cerevisiae CNCM I-3856 as a New Therapeutic Agent Against Oropharyngeal Candidiasis

Oropharyngeal candidiasis is a common opportunistic mucosal infection of the oral cavity, mainly caused by an overgrowth of Candida albicans. This infection can inhibit nutritional intakes and strongly affect quality of life. To date, standard therapeutic strategies involving the administration of antifungal drugs can bring several side effects, not least the emergence of drug-resistant strains. The purpose of this study is to investigate the effectiveness of Saccharomyces cerevisiae CNCM I-3856 (live or inactivated cells) against oropharyngeal candidiasis. Our results show that administration of S. cerevisiae CNCM I-3856 (live or inactivated cells) in the oral cavity of C57BL/6J mice resulted in a protective effect against oropharyngeal candidiasis. The strongest effect was obtained with live S. cerevisiae CNCM I-3856. This was related to: (1) a decrease in C. albicans load in the oral cavity, esophagus, stomach, and duodenum; (2) an early resolution of inflammatory process in the tongue; (3) a marked reduction in C. albicans virulence factors; and (4) a consistent increase in neutrophil antimicrobial capacity. These findings suggest that S. cerevisiae products are potentially beneficial in the treatment of oropharyngeal candidiasis.

Regulation of Candida albicans Hyphal Morphogenesis by Endogenous Signals

Candida albicans is a human commensal fungus that is able to assume several morphologies, including yeast, hyphal, and pseudohyphal. Under a range of conditions, C. albicans performs a regulated switch to the filamentous morphology, characterized by the emergence of a germ tube from the yeast cell, followed by a mold-like growth of branching hyphae. This transition from yeast to hyphal growth has attracted particular attention, as it has been linked to the virulence of C. albicans as an opportunistic human pathogen. Signal transduction pathways that mediate the induction of the hyphal transcription program upon the imposition of external stimuli have been extensively investigated. However, the hyphal morphogenesis transcription program can also be induced by internal cellular signals, such as inhibition of cell cycle progression, and conversely, the inhibition of hyphal extension can repress hyphal-specific gene expression, suggesting that endogenous cellular signals are able to modulate hyphal gene expression as well. Here we review recent developments in the regulation of the hyphal morphogenesis of C. albicans, with emphasis on endogenous morphogenetic signals.

Characteristics of lingual papillae in diabetic rats

Diabetes mellitus (DM) is a metabolic disorder resulting with many different complications including soft tissue abnormalities in the oral cavity such as periodontitis and salivary and taste dysfunction. Previous studies also reported fungal and bacterial infections in oral cavity in these patients. This study aims to represent three dimentional morphologic ultrastructural changes of the diabetic rat tongue via scanning electron microscopy. Twenty-four (24) adult male Spraque-Dawley rats, (weight ranging between 200-250g) included in the study were randomly assigned into two groups: control rats were injected with intraperitoneally saline alone, experimental diabetes group received streptozotocin (STZ) (80mg/kg) administrated intraperitoneally. On month four, by the end of experimental period, all animals of each group were anesthetised. All tongues were dissected totally, postfixed in 2% osmium tetroxide and then dried by critical point drying before SEM analysis. Finally, superficial epithelial configurations of the lingual papillae in experimental diabetic rats were examined by scanning electron microscopy. Diabetes mellitus caused thickness, hyperceratosis and different epithelial changes, We observed yeast-like structures and bacterial colonisations on the papillar and epithelial structure of the tongue. The morphological atrophic changes of lingual mucosa and the median rhomboid glossitis (which is primary finding of candidal infection) are characteristic observations on the lingual mucosa of the streptozotocin treated rats.

Utilization of Hybrid Assembly Approach to Determine the Genome of an Opportunistic Pathogenic Fungus, Candida albicans TIMM 1768

Candida albicans TIMM1768 is a highly virulent strain utilized as a model organism for the study of gastrointestinal and oral candidiasis. Despite being a model strain, identification of its genetic determinants of pathogenesis is hindered by the unavailability of its genome sequence. In this study, we determined the genome sequence of C. albicans TIMM1768 using reads obtained from portable MinION and benchtop Ion PGM sequencers. Genome annotation and a comparative analysis with published genomes revealed that the TIMM1768 strain was close to Candida albicans CHN1, and we identified a significant number of genes encoding for pathogenesis. The availability of the C. albicans TIMM1768 genome will facilitate comparative genomic analysis of Candida species, including studies of its virulence mechanisms and the development of treatment strategies for severe candidiasis.

Chemical inhibitors of Candida albicans hyphal morphogenesis target endocytosis

Candida albicans is an opportunistic pathogen, typically found as a benign commensal yeast living on skin and mucosa, but poised to invade injured tissue to cause local infections. In debilitated and immunocompromised individuals, C. albicans may spread to cause life-threatening systemic infections. Upon contact with serum and at body temperature, C. albicans performs a regulated switch to filamentous morphology, characterized by emergence of a germ tube from the yeast cell followed by mold-like growth of branching hyphae. The ability to switch between growth morphologies is an important virulence factor of C. albicans. To identify compounds able to inhibit hyphal morphogenesis, we screened libraries of existing drugs for inhibition of the hyphal switch under stringent conditions. Several compounds that specifically inhibited hyphal morphogenesis were identified. Chemogenomic analysis suggested an interaction with the endocytic pathway, which was confirmed by direct measurement of fluid-phase endocytosis in the presence of these compounds. These results suggest that the activity of the endocytic pathway, which is known to be particularly important for hyphal growth, represents an effective target for hyphae-inhibiting drugs.

Oral Candida spp carriage and periodontal diseases in HIV-infected patients in Ribeirão Preto, Brazil

The majority of HIV-infected patients develop Candida spp-associated clinical oral lesions. Studies have shown that asymptomatic oral colonization of Candida spp may lead to oral lesions or become a source of disseminated infections. The aim of this study was to verify the effects of periodontal conditions on Candida spp prevalence and Candida spp carriage in the oral cavity of HIV-infected patients compared to non-infected patients. Twenty-five patients not infected with HIV and 48 HIV-infected patients were classified according to periodontal conditions as being periodontal healthy or with periodontal disease. Candida spp carriage and classification were performed in oral rinse samples. Viral load and CD4+ T lymphocyte (CD4+L) counts were performed in blood samples from HIV-infected patients. No differences in Candida spp prevalence related to HIV status or periodontal condition were detected. However, Candida spp carriage was increased in periodontally affected HIV-infected patients when compared to periodontally healthy HIV-infected patients (p= 0.04). Periodontally healthy HIV-infected patients presented Candida spp carriage in similar levels as healthy or periodontally affected non-HIV-infected patients. Candida spp carriage was correlated with CD4+L counting in HIV-infected patients. We concluded that periodontal disease is associated with increased Candida spp carriage in HIV-infected patients and may be a predisposing factor to clinical manifestations of candidiasis.

Essential oil of Melaleuca alternifolia for the treatment of oral candidiasis induced in an immunosuppressed mouse model

Background

The search for alternative therapies for oral candidiasis is a necessity and the use of medicinal plants seems to be one of the promising solutions. The objective of this study was to evaluate the in vitro and in vivo effects of the essential oil of Melaleuca alternifolia on Candida albicans.

Methods

The minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) of M. alternifolia were determined by the broth microdilution assay. For the in vivo study, twelve immunosuppressed mice with buccal candidiasis received topical applications of M. alternifolia with MBEC. After treatment, yeasts were recovered from the mice and quantified (CFU/mL). Mice were killed for morphologic analysis of the tongue dorsum by optical and scanning electron microscopy. Data were analyzed using Student’s t test or Mann-Whitney test.

Results

The MIC of M. alternifolia was 0.195% and the MBEC was 12.5%. Treatment with M. alternifolia achieved a 5.33 log reduction in C. albicans and reduced the microscopic lesions of candidiasis.

Conclusions

M. alternifolia oil at a 12.5% was effective to eradicate a C. albicans biofilm formed in vitro and to reduce yeasts of C. albicans in an immunosuppressed mouse model.

Pathological analysis of the Candida albicans-infected tongue tissues of a murine oral candidiasis model in the early infection stage

OBJECTIVE

The early pathological process of Candida infection and immunological responses in tongues of the mice with experimental oral candidiasis was analysed.

METHODS

CD-1 mice, pretreated by prednisolone were orally inoculated with Candida albicans. Symptoms were monitored by measuring the area of white tongue coating and number of viable Candida cells in oral cavity. The histopathological analysis was carried by PAS-stain and immunofluorescent staining. IL-4, IL-12p70, IFN-γ, TNF-α in recovered from the homogenates of the tongues were measured by ELISA.

RESULTS

The fungus invaded the tongue surface of the mice and white patches developed within 24h after inoculation. Histopathological examination indicated the presence of local acute inflammation in superficial tissues of tongues covered by mycelium of C. albicans. Pathological exacerbation was observed from 24 to 48 h after the inoculation and from then the symptoms of oral candidiasis appeared to move into the recovery phase. Inflammatory cells mainly consisting of neutrophils was accumulated and located under the lesions covered by Candida-hyphae. An increase in IL-12p70 and IFN-γ in tongue homogenates was observed at 48 h after inoculation.

CONCLUSIONS

The worst condition in the pathological process in experimental oral candidiasis was found 48 h after C. albicans inoculation. When the surface of the Candida-inoculated tongues was covered with Candida-hyphae, a dense accumulation of neutrophils was observed under the lesions and homogenates of the tongues contained increased levels of IL-12p70 and IFN-γ. These suggested that local pathological condition of Candida-infected tongues may be affected by neutrophils accumulation and increased levels of some cytokines.

Efficacy of Fungiflora Y staining for the diagnosis of oral erythematous candidiasis

OBJECTIVE

The purpose of this study was to investigate the efficacy of Fungiflora Y staining (fluorescent stain) for the diagnosis of erythematous candidiasis.

SUBJECTS AND METHODS

This study enrolled 48 patients who were diagnosed with erythematous candidiasis and who underwent fungal culture and microscopic examination of a smear specimen stained with CytoQuick (modification of the Giemsa stain) and Fungiflora Y. Fungiflora Y staining was observed using a portable fluorescent microscope (CyScope(®)). The sensitivity, specificity and positive and negative predictive values were calculated using fungal culture as the gold standard test. Accuracy was calculated, and the difference between the CytoQuick and Fungiflora Y groups was examined using contingency tables and the chi-square test.

RESULTS

The sensitivity and specificity of the CytoQuick stain was 0.51 and 0.91, respectively; the positive predictive value was 0.95, and the negative predictive value was 0.36. The sensitivity and specificity of the Fungiflora Y stain was 0.84 and 1.0, respectively; the positive predictive value was 1.00, and the negative predictive value was 0.65. The accuracy of Fungiflora Y (0.88) was superior to that of CytoQuick (0.60) (p = 0.0052).

CONCLUSIONS

Microscopic examinations of smear specimens using a combination of Fungiflora Y staining and the CyScope(®) portable fluorescent microscope was found to be useful for the diagnosis of oral erythematous candidiasis.

The relationship between oral hygiene and oral colonization with Candida species in healthy adult subjects*

Poor oral hygiene has been frequently suggested as a predisposing factor for oral candidal colonization, but the convincing evidence is lacking.

OBJECTIVE

To assess and compare oral candidal colonization, both quantitatively and qualitatively, in groups of healthy dentate subjects with different levels of oral hygiene as determined by the plaque index (PI) and gingival index (GI) scores.

METHODS

The concentrated oral rinse technique was used to isolate Candida species from 149 healthy dentate subjects. Candida species were cultured on Sabouraud's dextrose agar plates and identified by germ-tube test and the automated Vitek(R) system biochemical yeast card. According to the PI and GI scores, subjects were divided into different groups of oral hygiene level.

RESULTS

Candida species were isolated from 86 (57.7%) subjects. The prevalence of candidal carriage increased significantly as a function of age (P = 0.023), but was comparable between males and females (58.7% and 56.7% respectively; P = 0.87). Oral candidal carriage rate and density were not affected by the levels of dental plaque or gingival condition. The prevalence of oral candididal carriage was significantly higher in the subjects who were not using dental floss compared with those who were using dental floss (P = 0.032).

CONCLUSION

Oral hygiene status, as determined by the PI and the GI scores per se, does not affect oral candidal colonization in healthy dentate subjects.

Fungal pathogenicity and morphological switches

The virulence of Candida albicans, a major human fungal pathogen, has been considered dependent on the ability to transition between different morphologies. A new study reports a screen of C. albicans mutants that demonstrates that pathogenesis can be dissociated from morphological switching and in vitro growth rate.