Amphotericin B-induced in vitro postantifungal effect on Candida species of oral origin

Postantifungal Effect of Antifungal Drugs against Candida: What Do We Know and How Can We Apply This Knowledge in the Clinical Setting?

The study of the pharmacological properties of an antifungal agent integrates the drug pharmacokinetics, the fungal growth inhibition, the fungicidal effect and the postantifungal activity, laying the basis to guide optimal dosing regimen selection. The current manuscript reviews concepts regarding the postantifungal effect (PAFE) of the main classes of drugs used to treat Candida infections or candidiasis. The existence of PAFE and its magnitude are highly dependent on both the fungal species and the class of the antifungal agent. Therefore, the aim of this article was to compile the information described in the literature concerning the PAFE of polyenes, azoles and echinocandins against the Candida species of medical interest. In addition, the mechanisms involved in these phenomena, methods of study, and finally, the clinical applicability of these studies relating to the design of dosing regimens were reviewed and discussed. Additionally, different factors that could determine the variability in the PAFE were described. Most PAFE studies were conducted in vitro, and a scarcity of PAFE studies in animal models was observed. It can be stated that the echinocandins cause the most prolonged PAFE, followed by polyenes and azoles. In the case of the triazoles, it is worth noting the inconsistency found between in vitro and in vivo studies.

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.

Association between glycemic status and oral Candida carriage in patients with prediabetes

OBJECTIVE

This study assessed the association between glycemic status and oral Candida carriage among patients with prediabetes.

STUDY DESIGN

This was a comparative study of oral Candida carriage among individuals with prediabetes. Oral yeast samples were collected from 150 individuals: group A was 43 patients with prediabetes (fasting blood glucose levels and hemoglobin A1c, 100 to 125 mg/dL and ≥5%, respectively); group B was 37 individuals previously considered prediabetic but having fasting blood glucose levels <100 mg/dL and hemoglobin A1c <5%; and group C was 70 medically healthy individuals. Oral yeasts were identified using standard techniques. Unstimulated whole salivary flow rate and number of missing teeth were recorded.

RESULTS

Oral Candida was isolated from 100% of patients with prediabetes and from 65.7% of control participants. Candida albicans carriage was higher among patients with prediabetes (48.7%) (P < .01) and patients in group A (51.2%) (P < .01) than among controls (25.7%). Candida carriage, unstimulated whole salivary flow rate, and number of missing teeth were similar in groups A and B.

CONCLUSIONS

Oral Candida carriage was higher in patients with prediabetes than in controls and was independent of glycemic status in patients with prediabetes.

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.