The establishment of a community of oral bacteria that controls the growth of Candida albicans in a chemostat

Quantification and Pathogenicity of Candida albicans in Denture-Wearing and Nondenture-Wearing Elderly

Objective  The primary purpose of this study was to evaluate and compare the microbial loads and pathogenicity traits of oral Candida albicans in denture-wearing (DW; n = 15) and nondenture-wearing (NDW; n = 15) elderly persons.

Materials and Methods  The fungal counts of the saliva, tongue dorsa, and prosthesis-fitting surfaces of the participants were assessed using real-time polymerase chain reaction to compare the quantity and expression of selected C. albicans biofilm-associated genes ( ALS3 , HWP1 , and YWP1 ).

Statistical Analysis  The obtained data were analyzed by one-way analysis of variance, followed by Bartlett’s test. When appropriate, the Student’s t -test was also used; a value of p < 0.05 was considered statistically significant.

Results  In both groups, the count of C. albicans was found to be significantly higher in saliva than in other oral samples. The expression of the hypha-specific genes ( ALS3 and HWP1 ) in the tongue dorsa was higher in the DW group ( p < 0.05), whereas the transcription level of the yeast-specific gene ( YWP1) was significantly higher in the NDW group.

Conclusion  Both tongue dorsa and dentures appear to be sharing factors that are important for C. albicans biofilm growth in abiotic and biotic oral surfaces of the elderly.

Transcriptome-based characterization of interactions between Saccharomyces cerevisiae and Lactobacillus delbrueckii subsp. bulgaricus in lactose-grown chemostat cocultures

Mixed populations of Saccharomyces cerevisiae yeasts and lactic acid bacteria occur in many dairy, food, and beverage fermentations, but knowledge about their interactions is incomplete. In the present study, interactions between Saccharomyces cerevisiae and Lactobacillus delbrueckii subsp. bulgaricus, two microorganisms that co-occur in kefir fermentations, were studied during anaerobic growth on lactose. By combining physiological and transcriptome analysis of the two strains in the cocultures, five mechanisms of interaction were identified. (i) Lb. delbrueckii subsp. bulgaricus hydrolyzes lactose, which cannot be metabolized by S. cerevisiae, to galactose and glucose. Subsequently, galactose, which cannot be metabolized by Lb. delbrueckii subsp. bulgaricus, is excreted and provides a carbon source for yeast. (ii) In pure cultures, Lb. delbrueckii subsp. bulgaricus grows only in the presence of increased CO2 concentrations. In anaerobic mixed cultures, the yeast provides this CO2 via alcoholic fermentation. (iii) Analysis of amino acid consumption from the defined medium indicated that S. cerevisiae supplied alanine to the bacterium. (iv) A mild but significant low-iron response in the yeast transcriptome, identified by DNA microarray analysis, was consistent with the chelation of iron by the lactate produced by Lb. delbrueckii subsp. bulgaricus. (v) Transcriptome analysis of Lb. delbrueckii subsp. bulgaricus in mixed cultures showed an overrepresentation of transcripts involved in lipid metabolism, suggesting either a competition of the two microorganisms for fatty acids or a response to the ethanol produced by S. cerevisiae. This study demonstrates that chemostat-based transcriptome analysis is a powerful tool to investigate microbial interactions in mixed populations.

Tongue coating and tongue brushing: a literature review

The present paper reviews the role of the tongue as a habitat for oral microorganisms and the potential need for tongue cleaning as part of daily oral hygiene. In addition tongue coating is described. Many microorganisms have been found colonizing the dorsum of the tongue. Some studies find a positive effect to tongue brushing on bacterial counts on the tongue. On the other hand there are also studies that do not find any differences in bacterial counts before or after tongue brushing. Bacteria colonizing the tongue and periodontal pockets play an important role in the production of volatile sulphur compounds in periodontal health and disease. These compounds can be the cause of oral malodour. The amount of tongue coating in patients complaining of halitosis was significantly greater than in patients without halitosis. Tongue brushing on a regular basis, particular aiming at removing the coating on the dorsum of the tongue, has been found to be fruitful in reducing oral malodour. Studies investigating the role of tongue brushing and plaque accumulation or gingival inflammation show conflicting results. It is clear that the tongue forms the largest niche for microorganims in the oral cavity. However, on the basis of literature, there appears to be no data to justify the necessity to clean the tongue on a regular basis. One exception would be oral malodour.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Yeasts in periodontal pockets

OBJECTIVES

The presence of yeasts in periodontal pockets has been described in a few studies. The association between yeasts and putative periodontal pathogens is not well described. This study aims at assessing the prevalence of yeasts in periodontal pockets and possible associations with the clinical conditions of the sampled sites and other micro-organisms present.

MATERIAL AND METHODS

2 subject groups form the basis for this study. The 1st comprises results from microbiological samples from periodontal pockets of 128 subjects. The 2nd originates from 126 periodontal patients with untreated pockets. Microbiological identification was performed after cultivation on blood and Sabouraud agar plates, and "checkerboard" DNA-DNA hybridisation.

RESULTS

The prevalence of subjects with yeasts in the pockets was 15.6% and 17.5% in the 2 groups respectively and was inconsistent according to gender. No correlation was found between age and the presence of yeasts. Eubacterium saburreum was weakly correlated with presence of yeasts (r=0.194 p=0.03). Yeasts were rarely found in both samples from the same individual.

CONCLUSIONS

Our results indicate that yeasts can be expected to be present in periodontal pockets in one out of 6 periodontal patients independent of gender and age. Eubacterium saburreum seems to occur frequently together with yeasts.

Bacterial flora accompanying Candida yeasts in clinical specimens

From 1986 to 1988, in the prefluconazole era, 67,765 clinical specimens from the Göttingen University Hospital were investigated for bacteria and fungi in our institution. Oral and throat swabs, respiratory secretions, gastric juices, faeces, urine, genital swabs, blood, wound secretions and skin swabs were analysed for yeast-like fungi, and opportunistic or pathogenic bacteria. A total of 5195 specimens (7.7%) yielded Candida spp. alone or in combination with bacteria (fungal (F-) group) and 62,570 specimens yielded bacteria only or remained sterile (non-fungal group, N-group). Elevated rates of accompanying bacteria were detected with Candida spp. colonizing blood, urine, and skin. Among the dominant bacterial isolates, the distribution of staphylococci and enterococci did not reflect a distinct association pattern. Among the enterobacterial isolates from patients in intensive care, colonization patterns of the throat, gastric juices, and faeces reflected the use of a selective decontamination of the digestive tract (SDD). A statistically significant association between Candida and enterobacteria of the genus Enterobacter which was unaffected by SDD, was observed throughout this study. Such an association pattern was also observed, to a lesser extent, with the related genera Klebsiella and Serratia, but not with Escherichia coli.