Tw Macfarlane

Factors affecting the phospholipase activity of Candida species in vitro

The phospholipase activity of 41 isolates of oral Candida species was determined by a plate assay. Seventy nine per cent of the C. albicans isolates were phospholipase producers whereas none of the C. tropicalis, C. glabrata or C. parapsilosis isolates produced the enzyme. The degree of phospholipase activity (Pz value) of individual isolates was remarkably constant despite the large variation in activity among different isolates. Experiments with 10 phospholipase positive C. albicans isolates indicate that phospholipase production in vitro is limited to a narrow pH range (c. 3.6-4.7) and is suppressed by increasing concentrations of sucrose and galactose in the media (r = 0.9). Hence, candidal phospholipases seem to play a complex role in the aetiopathology of human candidoses.

Factors affecting the in-vitro adherence of Candida albicans to acrylic surfaces.

The fitting surface of the upper denture is the main reservoir of yeasts in patients with chronic atrophic candidosis. Because little is known about the adhesion of Candida albicans to acrylic surfaces, an in-vitro technique was used to investigate the effect of sucrose, glucose, lactose, xylitol, mixed and parotid saliva, serum and Streptococcus salivarius on adhesion. Enhancement of candidal adhesion was seen on serum-coated acrylic strips and by yeasts incubated in sucrose, glucose and a dialysate of Strep, salivarius. Pre-coating acrylic strips with mixed saliva, 2 per cent chlorhexidine and Strep, salivarius reduced adhesion, while pre-coating strips with 0.2 per cent chlorhexidine and parotid saliva or pre-incubating yeasts in lactose and xylitol had no significant effect on adhesion. This study suggests that the factors involved in the adhesion of C. albicans to acrylic surfaces are complex, and that they may play an important role in the aetiology of chronic atrophic candidosis.

An in-vitro study of the adherence of Candida albicans to acrylic surfaces

Abstract An in-vitro system was designed to assess quantitatively the adhesion of Candida albicans to acrylic surfaces. Clear acrylic strips were placed in yeast suspensions and the number of yeasts attached per unit area was counted microscopically. A significant positive correlation was found between the concentrations of yeast in the suspension and their adhesion to the acrylic strips. Pre-incubation with sucrose greatly increased the adherence of C. albicans to the acrylic strips, and there was a direct linear increase in adhesion with increasing sucrose concentrations. The enhanced adhesion of yeasts induced by sucrose disappeared when Candida were heat-killed prior to incubation in a sucrose-containing medium. These observations, together with electron-microscopic studies, suggest that an extracellular metabolic product of the organism could be responsible for the enhanced adhesion associated with sucrose. The system can be effectively used to study the influence of other intra-oral factors on the adhesion of C. albicans to acrylic surfaces.

The Effect of Chlorhexidine and Benzydamine Mouthwashes On Mucositis Induced by Therapeutic Irradiation

A variety of mouthwashes are frequently used in the management of irradiation-induced mucositis. Benzydamine has recently been introduced for alleviating this condition. Its efficacy as a mouthwash was compared with chlorhexidine in two groups of patients receiving radiotherapy for oral carcinoma. Mucositis and pain were recorded over a 6 week period and oral carriage of Candida species, coliforms and Staphylococcus aureus was assessed using an oral rinse technique. There was no significant difference in the mucositis scores, overall pain scores or the yeast and bacterial species isolated between the two treatment groups. However, 58% (7 out of 12) and 92% (12 out of 13) patients reported oral discomfort when rinsing the mouth with chlorhexidine and benzydamine, respectively. In both groups, the most common coliform isolated was Klebsiella pneumoniae and the carriage of yeasts was significantly greater than that of coliforms. These results indicate that, although the individual patient acceptance of chlorhexidine is better than benzydamine, there is little difference between the two mouthwashes both in controlling pain and mucositis or in the oral carriage of the micro-organisms studied.

Factors affecting the in-vitro adherence of the fungal oral pathogen Candida albicans to epithelial cells of human origin

An in-vitro technique was used to investigate the effects of oral commensal bacteria, serum, saliva, germ-tube formation and pH on the adherence of two strains of C. albicans to HeLa cells. Streptococcus salivarius and Streptococcus mitior reduced candidal adhesion whereas Streptococcus mutans had no significant effect. A mixed salivary pellicle on HeLa cells significantly enhanced candidal adhesion and a serum layer had no effect. Yeasts pre-incubated in whole saliva for 3 h showed significantly greater adhesion to HeLa and human embryonic kidney epithelial cells than yeasts in phosphate-buffered saline. The adherence of hyphal phase candida was significantly greater than in the blastospore phase. Adhesion varied with the pH of the test medium, maximal adherence was at pH 3 with less under neutral pH conditions. The factors involved in the adhesion of C. albicans to epithelial surfaces are complex and may play a rôle in the aetiopathology of human mucosal candidoses.

The adhesion of the yeast Candida albicans to epithelial cells of human origin in vitro

Abstract Monolayers of HeLa cells were incubated with Candida suspensions and the number of adherent yeasts per unit area of epithelial cells counted microscopically. Adhesion was proportional to the incubation time and the yeast concentration in the suspension. Preincubation of Candida with sucrose facilitated their adhesion, there being a linear enhancement with increasing sucrose concentrations. The sucrose-facilitated adhesion disappeared when the yeasts were killed prior to incubation in a sucrose-containing medium, suggesting that an extracellular metabolic product could be responsible. On comparison of the adhesion of yeasts to viable and non-viable HeLa cells, greater adhesion to non-viable cells was observed. This experimental system can be used to study parameters influencing candidal adhesion to epithelial surfaces.

The relationship between colonisation, secretor status and in-vitro adhesion of Candida albicans to buccal epithelial cells from diabetics

This study investigated whether oral candida infection in diabetics and adhesion of Candida albicans to buccal epithelial cells in vitro were related. Buccal cells from 50 patients with diabetes mellitus showed a significant increase in adhesion of C. albicans strain CDS 88 compared with those collected from 50 non-diabetic controls matched for age, sex and denture status. Oral candida carriage, candida infection and secretor status were also investigated in both groups. The frequency of carriage was increased, but not significantly, and there was a significantly higher incidence of candida infection in diabetic patients compared with controls. Diabetic patients who were non-secretors had a significantly increased frequency of oral candida carriage.

The effect of cytotoxic therapy on saliva and oral flora

Oral complications of cytotoxic therapy result from direct mucosal damage and, indirectly, occur as a consequence of immunosuppression. Such problems are further exacerbated as a result of associated xerostomia and secondary infection. Therefore, the aims of this study were to examine the salivary volume and composition (amylase, IgA, and lysozyme) together with the oral carriage of potential pathogens in patients receiving cytotoxic therapy. A pilot study comparing healthy controls with patients on chemotherapy for malignant conditions indicated that there were differences between the two groups. Therefore, a longitudinal study was initiated and twelve patients were assessed prior to and 4 and 12 weeks after the start of cytotoxic therapy. The 10-minute forced-spitting salivary volume and amylase and IgA levels all declined significantly over the 12-week period. Lysozyme content did not change. A quantitative increase in the oral carriage of Candida species, coliforms, and Staphylococcus aureus was also observed during therapy. Hence, it is concluded that cytotoxic chemotherapy results in a decreased salivary flow, a reduction in salivary amylase and IgA, and an increase in the oral carriage of opportunistic pathogens.

The proteolytic potential of Candida albicans in human saliva supplemented with glucose

The production of proteases by Candida albicans in batch cultures of human saliva supplemented with glucose was investigated with two clinical strains of Candida and both individual and pooled samples of whole saliva from volunteers. Salivary proteolysis during a 48-h period was estimated by biochemical and isoelectric focusing techniques. Candidal growth in saliva was associated with acid production and salivary proteolysis and there was a highly significant positive correlation between these two activities. Neither candidal growth nor proteolysis was observed in glucose-free control samples and with one strain of Candida cultured in the saliva of one individual. Isotachophoretic analysis of culture liquor showed a significant increase in acetate and pyruvate ions. The oral cavity provides niches that have a low pH and are periodically supplemented with dietary carbohydrates. The acidic proteases of C. albicans may play a role in the pathogenesis of oral candidoses.

Effect of saliva and serum on the adherence of Candida species to chlorhexidine-treated denture acrylic

The effect of saliva and serum on the adherence of five strains of Candida albicans and one each of C. tropicalis and C. glabrata to chlorhexidine-pretreated acrylic was measured in vitro. A four-fold dilution of saliva or serum significantly inactivated the fungicidal effect of chlorhexidine gluconate. Pretreatment of the acrylic with unstimulated mixed saliva for 30 min led to a reduced adherence for all the Candida strains tested, whilst a similar pretreatment with serum slightly increased adhesion. Moreover treatment of saliva- or serum-coated acrylic with chlorhexidine gluconate 2% reduced adherence by between 19% and 86%. The inhibition of yeast adherence by chlorhexidine persisted for up to 19 days after the exposure of the acrylic strips to the disinfectant.