Cell surface hydrophobicity of oral Candida dubliniensis isolates following limited exposure to sub-therapeutic concentrations of chlorhexidine gluconate

Role of Cell Surface Hydrophobicity in the Pathogenesis of Medically-Significant Fungi

Cell surface hydrophobicity (CSH) is an important cellular biophysical parameter which affects both cell-cell and cell-surface interactions. In dimorphic fungi, multiple factors including the temperature-induced shift between mold and yeast forms have strong effects on CSH with higher hydrophobicity more common at the lower temperatures conducive to filamentous cell growth. Some strains of Cryptococcus neoformans exhibit high CSH despite the presence of the hydrophilic capsule. Among individual yeast colonies from the same isolate, distinct morphologies can correspond to differences in CSH. These differences in CSH are frequently associated with altered virulence in medically-significant fungi and can impact the efficacy of antifungal therapies. The mechanisms for the maintenance of CSH in pathogenic fungi remain poorly understood, but an appreciation of this fundamental cellular parameter is important for understanding its contributions to such phenomena as biofilm formation and virulence.

Does oral care with chlorhexidine reduce ventilator-associated pneumonia in mechanically ventilated adults?

Oral colonisation by pathogens contributes to contracting ventilator-associated pneumonia (VAP). The aim of this review was to determine whether the use of the antiseptic chlorhexidine in the intra-oral cavity reduced its incidence in the critically ill, mechanically ventilated adult. The findings from this review led to the conclusion that chlorhexidine reduced the occurrence of VAP. Although a recommendation to implement the use of intra-oral chlorhexidine for mechanically-ventilated patients within critical care can be made, further exploration into required frequency and method of administration would be beneficial to reduce unnecessary exposure and hinder pathogenic resistance.

The Glutaredoxin Gene, grxB, Affects Acid Tolerance, Surface Hydrophobicity, Auto-Aggregation, and Biofilm Formation in Cronobacter sakazakii

Cronobacter species are foodborne pathogens that can cause neonatal meningitis, necrotizing enterocolitis, and sepsis; they have unusual abilities to survive in environmental stresses such as acid stress. However, the factors involved in acid stress responses and biofilm formation in Cronobacter species are poorly understood. In this study, we investigated the role of grxB on cellular morphology, acid tolerance, surface hydrophobicity, auto-aggregation (AAg), motility, and biofilm formation in Cronobacter sakazakii. The deletion of grxB decreased resistance to acid stresses, and notably led to weaker surface hydrophobicity, AAg, and biofilm formation under normal and acid stress conditions, compared with those of the wild type strain; however, motility was unaffected. Therefore, grxB appears to contribute to the survival of C. sakazakii in acid stresses and biofilm formation. This is the first report to provide valuable evidence for the role of grxB in acid stress responses and biofilm formation in C. sakazakii.

Impact of short-term exposure of antifungal agents on hemolysin activity of oral Candida dubliniensis isolates from Kuwait and Sri Lanka

OBJECTIVE

Ability to produce hemolysin by Candida species is an important determinant of its pathogenicity. Candida dubliniensis is implicated in the causation of oral candidosis, which can be treated with polyene, echinocandin, and azole groups of antifungal agents as well as chlorhexidine. After oral application, however, the concentrations of these agents tend to decrease quickly to subtherapeutic levels due to the peculiarity of the oral environment. In this study, we have evaluated the effect of short-term exposure of sublethal concentrations of these drugs on hemolysin production by oral C. dubliniensis isolates obtained from two different geographical locale.

MATERIALS AND METHODS

Twenty C. dubliniensis oral isolates obtained from Kuwait and Sri Lanka were exposed to sublethal concentrations of nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine for 1 h. Thereafter, the drugs were removed by dilution and the hemolysin production determined by a previously described plate assay.

RESULTS

Hemolysin production of these isolates was significantly suppressed with a percentage reduction of 17.09, 16.45, 17.09, 11.39, 8.23 and 12.03 following exposure to nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine, respectively.

CONCLUSION

Brief exposure to sublethal concentrations of drugs with antifungal properties appears to reduce the pathogenic potential of C. dubliniensis isolates by suppressing hemolysin production.

In vitro Impact of Limited Exposure to Subtherapeutic Concentrations of Chlorhexidine Gluconate on the Adhesion-Associated Attributes of Oral Candida Species

OBJECTIVE

Candida albicans and its non-albicans counterparts, such as C. tropicalis, C. krusei, C. glabrata and C. dubliniensis, are the major etiological agents of oral candidosis. Their adherence to buccal epithelial cells (BEC), denture acrylic surfaces (DAS) and cell surface hydrophobicity (CSH) are attributes associated with yeast colonization and infection. Chlorhexidine gluconate (CG) is a widely used antiseptic in dentistry. When administered, the diluent effect of saliva and the cleansing effect of the oral musculature reduce its bioavailability, compromising its efficacy. Hence, intraorally, Candida undergoes a transient exposure to high CG concentrations, and thereafter it is likely to be subtherapeutic. Therefore, the impact of CG on adhesion to BEC, DAS and CSH of different oral Candida species was investigated following brief exposure to three subtherapeutic concentrations of CG.

MATERIALS AND METHODS

Ten oral isolates of each of the above five Candida species obtained in Kuwait from oral rinse samples were exposed to 0.00125, 0.0025 and 0.005% CG for 30 min. Subsequently, the yeast adhesion to BEC, DAS and CSH was determined. The data were analyzed using ANOVA Dunnett's t tests.

RESULTS

Exposure to the lowest dilution (0.00125%) of CG did not elicit a noteworthy collective suppression on all three adhesion traits evaluated. Exposure to 0.0025% CG curtailed the adhesion to BEC, DAS and CSH of Candida species by 50.89, 40.79 and 24.58%, respectively (p < 0.001). Exposure to the highest concentration (0.005%) of CG reduced the adhesion to BEC, DAS and CSH of Candida species by 64.68, 54.59 and 50%, respectively (p < 0.001).

CONCLUSIONS

Brief exposure to subtherapeutic concentrations of CG suppressed the adhesion to BEC, DAS and CSH of oral Candida species, indicating probable pharmacodynamics that may potentiate its antiseptic properties.

In Vitro Antimicrobial and Antiproliferative Activity of Amphipterygium adstringens

Amphipterygium adstringens is a plant widely used in Mexican traditional medicine for its known anti-inflammatory and antiulcer properties. In this work, we evaluated the in vitro antimicrobial and antiproliferative activities of the methanolic extract of A. adstringens against oral pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Candida albicans, and Candida dubliniensis, using microdilution (MIC) and agar diffusion methods (MBC), and the antiproliferative activity evaluating total growth inhibition (TGI) by staining the protein content with sulforhodamine B (SRB), using nine human cancer cell lines. Crude extract (CE) of A. adstringens showed some degree of activity against one or more of the strains with a MIC from 0.125 mg/mL to 63 mg/mL and MBC from 1.6 to 6.3 mg/mL and cytotoxic activity, particularly against NCI-ADR/RES, an ovarian cell line expressing multiple resistance drugs phenotype. The CE is a complex mixture of possible multitarget metabolites that could be responsible for both antimicrobial and antiproliferative activities, and further investigation is required to elucidate the identity of active compounds. Nevertheless the CE itself is useful in the development of new antimicrobial treatment based on natural products to prevent oral diseases and as alternative natural source for cancer treatment and prevention.

Glutathione as a promising anti-hydrophobicity agent against Malassezia spp

The genus Malassezia has recently attracted wide attention in medical microbiology and dermatology as a pathogen. They are lipophilic yeasts possessing high level of cell surface hydrophobicity (CSH). L-glutathione (GSH) is a ubiquitous antioxidant which offers protection against microbial infections. This study is intended to investigate the role of GSH as a potential anti-hydrophobicity agent against Malazessia spp. Microbial adherence to hydrocarbon assay was performed to assess the anti-hydrophobicity activity (AHA) of GSH against four Malassezia spp. The assay revealed that GSH at 400 μg ml(-1) concentration inhibited CSH, ranging from 84% to 95% in M. furfur, M. globosa, M. restricta and M. sympodialis without killing the cells. The AHA of GSH was corroborated by auto-aggregation assay and zeta-potential measurement, through which delayed cell aggregation was observed due to reduction in CSH level and not by modification in cell surface charge. In addition, colony-forming unit assay was performed in which 62-93% of CSH reduction was observed in Malassezia spp. tested. Furthermore, GSH treatment enhanced the sensitivity of Malassezia spp. towards human blood at the rate of 64-72%. The AHA was further confirmed through Fourier transform infrared analysis. Thus, this study portrays GSH as a prospective therapeutic alternative for Malassezia-mediated infections.

In vitro postantifungal effect, adhesion traits and haemolysin production of Candida dubliniensis isolates following exposure to 5-fluorocytosine

The phenomenon of postantifungal effect (PAFE), which is the suppression of candidal growth following brief exposure to antifungal agents, is linked with candidal pathogenicity. Adhesion to buccal epithelial cells (BEC), germ tube (GT) formation and relative cell surface hydrophobicity (CSH) are all adhesion traits of candidal pathogenicity. Ability to produce haemolysin by Candida species is also a determinant of its pathogenicity. There is no information on either the PAFE or its impact on adhesion traits and haemolysin production of oral Candida dubliniensis isolates following exposure to 5-fluorocytosine (5-FC). Hence, the focus of this investigation was to research the in vitro PAFE, adhesion to BEC, GT formation, relative CSH and haemolysin production on 20 C. dubliniensis isolates following exposure to 5-FC. Following obtaining the minimum inhibitory concentration (MIC) of 5-FC, isolates of C. dubliniensis were exposed to sub-lethal concentrations (×3 MIC) of 5-FC for 1 h. After this brief exposure, the antimycotic was removed and PAFE, adhesion to BEC, GT formation, relative CSH and haemolysin production was determined by formerly described in vitro methods. MIC (μg/ml) of C. dubliniensis isolates to 5-FC ranged from 0.002 to 0.125. The mean PAFE (hours) elicited by 5-FC on C. dubliniensis isolates was approximately 1 h. Exposure to 5-FC suppressed the ability of C. dubliniensis isolates to adhere BEC, GT formation, relative CSH and haemolysin activity by a mean percentage reduction in 50.98%, 29.51%, 36.79% and 12.75% (P < 0.001 for all) respectively. Therefore, brief exposure of C. dubliniensis isolates to 5-FC appears to exert an antifungal effect by subduing its growth, adhesion traits as well as haemolysin production.

In vitro adhesion of oral Candida dubliniensis isolates to acrylic denture surfaces following brief exposure to sub-cidal concentrations of polyenes, azoles and chlorhexidine

OBJECTIVES

We aimed to investigate the effect of brief exposure to sub-cidal concentrations of nystatin, amphotericin B, ketoconazole, fluconazole and chlorhexidine gluconate on the adhesion of oral Candida dubliniensis isolates to the surface of acrylic dentures.

METHODS

After determining the minimum inhibitory concentration of each drug, 20 oral isolates of C. dubliniensis were exposed to sub-cidal concentrations of the drugs for 1 h. The drugs were then removed by dilution, and the adhesion of the isolates to denture acrylic strips was assessed by an in vitro adhesion assay.

RESULTS

Compared to the controls, exposure to nystatin, amphotericin B, ketoconazole, fluconazole and chlorhexidine gluconate suppressed the ability of C. dubliniensis isolates to adhere to acrylic denture surfaces with a reduction of 74.68, 74.27, 57.31, 44.57 and 56.53% (p < 0.001 for all drugs), respectively.

CONCLUSIONS

Brief exposure to sub-cidal concentrations of anti-mycotics suppressed the adhesion of C. dubliniensis oral isolates to acrylic denture surfaces.

Candida albicans adherence to denture base material: chemical disinfection and the effect of acquired salivary pellicle formation

PURPOSE

The aim of this study was to evaluate the effect of 1% sodium hypochlorite (H1%) and 4% chlorhexidine gluconate (CG4%) on the adhesion of Candida albicans to denture base acrylic resins, as well as to verify the effect of the acquired salivary pellicle (ASP) formation on this process.

MATERIALS AND METHODS

A total of 300 acrylic specimens were immersed in distilled water (control) (n = 100), H1% (n = 100), or CG4% (n = 100) for 30 days. Twenty specimens were used in each experimental period (0, 1, 7, 15, 30 days). At the end of disinfection testing periods, 10 specimens of each group were exposed to human whole saliva to simulate ASP formation, and then all specimens were incubated with C. albicans ATTC 90028. Microorganism adhesion was analyzed by fluorescence microscopy, after staining with Acridine orange.

RESULTS

In the 30(th) disinfection cycle in relation to baseline, the H1% or CG4%, without ASP formation, reduced the C. albicans adhesion by approximately 80%; however, with ASP, this reduction after disinfection with H1% was higher (88%). The presence of ASP resulted in higher reduction of adhered fungal cells in comparison to resin without ASP, at the 1(st) H1% or CG4% disinfection cycle, as well as at 30(th) H1% disinfection cycles.

CONCLUSIONS

Our results suggest that the presence of saliva might influence the adhesion of C. albicans and improve the effectiveness of methods to reduce fungal adhesion.

Post-antifungal effect and adhesion to buccal epithelial cells of oral Candida dubliniensis isolates subsequent to limited exposure to amphotericin B, ketoconazole and fluconazole

AIM

The post-antifungal effect (PAFE) of Candida and its adherence to oral mucosal surfaces are important determinants of candidal pathogenicity. Candida dubliniensis is allied with recurrent oral candidosis. Oral candidosis can be treated with amphotericin B, ketoconazole and fluconazole. There is no information on the PAFE and its impact on adhesion to oral buccal epithelial cells (BEC) of oral C. dubliniensis isolates. Therefore, the main objective was to reconnoiter the PAFE and adhesion to BEC of 20 C. dubliniensis isolates following brief exposure to aforementioned antimycotics.

METHODS

After determining the minimum inhibitory concentration (MIC), C. dubliniensis isolates were exposed to sub-lethal concentrations of these drugs for 1 h. Following subsequent drug removal, the PAFE and adhesion to BEC, was determined by a turbidometric method, and an adhesion assay, respectively.

RESULTS

Minimum inhibitory concentration (μg/mL) to amphotericin B, ketoconazole and fluconazole, ranged from 0.002 to 0.125, 0.002 to 0.012 and 0.016 to 0.38, respectively. Amphotericin B and ketoconazole induced mean PAFE (hours) were 2.21 and 0.6, respectively. Fluconazole failed to produce a detectable PAFE. Compared to controls, amphotericin B, ketoconazole and fluconazole suppressed the ability to adhere to BEC with a mean percentage reduction of 74.31%, 49.80% (P < 0.0001) and 29.36% (P < 0.05), respectively.

CONCLUSIONS

Brief exposure to sub-lethal concentrations of aforementioned drugs would exert an antifungal effect by modifying the growth and adhesion of C. dubliniensis isolates.

Impact of brief and sequential exposure to nystatin on the germ tube formation and cell surface hydrophobicity of oral Candida albicans isolates from human immunodeficiency virus-infected patients

OBJECTIVE

To evaluate the impact of brief and sequential exposure to nystatin on the germ tube formation and cell surface hydrophobicity of oral isolates of Candida albicans obtained from patients infected with human immunodeficiency virus (HIV).

MATERIALS AND METHODS

After determining the minimum inhibitory concentration of nystatin, 10 oral isolates of C. albicans from 10 different HIV-infected patients were briefly (1 h) and sequentially (10 days) exposed to subtherapeutic concentrations of nystatin. Following a subsequent drug removal, the germ tube formation and cell surface hydrophobicity of these isolates were determined via a germ tube induction assay and an aqueous hydrocarbon assay, respectively. The data obtained from these assays for the control (unexposed to nystatin) and nystatin-exposed isolates were analyzed using Student's t tests.

RESULTS

The mean percentage reduction in the germ tube formation and cell surface hydrophobicity of the nystatin-exposed isolates compared to the controls was 30.12 ± 1.99 (p < 0.001) and 29.65 ± 2.33 (p < 0.001), respectively.

CONCLUSION

These data elucidate the possible pharmacodynamic mechanisms by which nystatin might operate in vivo in the modulation of candidal virulence.

The postantifungal effect of nystatin and its impact on adhesion attributes of oral Candida dubliniensis isolates

The postantifungal effect (PAFE) has an impact on candidal pathogenicity. However, there is no information on either the PAFE or its impact on adhesion traits of oral Candida dubliniensis isolates. Oral candidosis can be treated topically with nystatin. Adhesion to buccal epithelial cells (BEC), germ tube (GT) formation and relative cell surface hydrophobicity (CSH) are all colonisation attributes of candidal pathogenicity. Hence, the main objective of this study was to investigate the in vitro PAFE on 20 C. dubliniensis isolates following exposure to nystatin. In addition, the impact of nystatin-induced PAFE on adhesion to BEC, GT formation and relative CSH of C. dubliniensis isolates were also evaluated. After determining the minimum inhibitory concentration (MIC) of nystatin, C. dubliniensis isolates were exposed to sublethal concentrations of nystatin for 1 h. Following this exposure, the drug was removed and PAFE, adhesion to BEC, GT formation and relative CSH were determined by a previously described turbidometric method, adhesion assay, germ tube induction assay and biphasic aqueous-hydrocarbon assay respectively. MIC (μg/ml) of C. dubliniensis isolates to nystatin ranged from 0.09 to 0.78. The nystatin-induced mean PAFE (hours) on C. dubliniensis isolates was 2.17. Compared with the controls, exposure to nystatin suppressed the ability of C. dubliniensis isolates to adhere BEC, GT formation and relative CSH by a mean percentage reduction of 74.45% (P < 0.0001), 95.92% (P < 0.0001) and 34.81 (P < 0.05) respectively. Hence, brief exposure of C. dubliniensis isolates to nystatin would continue to wield an antifungal effect by suppressing growth as well as its adhesion attributes.

Changes in the cell surface hydrophobicity of oral Candida albicans from smokers, diabetics, asthmatics, and healthy individuals following limited exposure to chlorhexidine gluconate

OBJECTIVE

The objective of this study was to determine the cell surface hydrophobicity of 40 oral Candida albicans isolates obtained from smokers, diabetics, asthmatics using steroid inhalers, and healthy individuals, following brief exposure to subtherapeutic concentrations of chlorhexidine gluconate.

MATERIALS AND METHODS

Forty C. albicans oral isolates (10 isolates each from smokers, diabetics, asthmatics using steroid inhalers, and healthy individuals) were exposed to 3 subtherapeutic concentrations of chlorhexidine gluconate (0.00125, 0.0025, and 0.005%) for 30 min. Thereafter, the antiseptic was removed and the cell surface hydrophobicity was measured by a biphasic aqueous-hydrocarbon assay.

RESULTS

Compared to the unexposed controls, the cell surface hydrophobicity of C. albicans isolates was suppressed by 5.40% (p > 0.05), 21.17% (p < 0.05), and 44.67% (p < 0.05) following exposure to 0.00125, 0.0025, and 0.005% chlorhexidine gluconate, respectively.

CONCLUSIONS

A brief period of transient exposure to subtherapeutic concentrations of chlorhexidine gluconate may modulate the cell surface hydrophobicity of C. albicans isolates and thereby may reduce candidal pathogenicity.