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

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.

Impact of Brief Exposure to Drugs with Antifungal Properties on the Susceptibility of Oral Candida dubliniensis Isolates to Lysozyme and Lactoferrin

OBJECTIVE

Lysozyme and lactoferrin have anti-candidal activity. Candida dubliniensis is associated with oral candidiasis. Candida infections are managed with nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine. Candida species undergo a brief exposure to therapeutic agents in the mouth. There is no data on the influence of limited exposure to antimycotics on the sensitivity of C. dubliniensis to lactoferrin and lysozyme. Hence, this study observed the changes in the sensitivity of C. dubliniensis to anti-candidal action of lactoferrin and lysozyme after transitory exposure to sub-lethal concentrations of antifungals.

MATERIALS AND METHODS

After determination of the minimum inhibitory concentration (MIC), 20 C. dubliniensis isolates were exposed to twice the concentration of MIC of nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine for 1 h. Drugs were removed by dilution and thereafter the susceptibility of these isolates to lysozyme and lactoferrin was determined by colony-forming unit quantification assay.

RESULTS

Exposure of C. dubliniensis to nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine resulted in an increase in susceptibility to lysozyme by 9.45, 30.82, 30.04, 50.64, 55.60, and 50.18%, respectively (p < 0.05 to p < 0.001). Exposure of C. dubliniensis to nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine resulted in an increase in susceptibility to lactoferrin by 13.54, 16.43, 17.58, 19.60, 21.32, and 18.73, respectively (p < 0.05 to p < 0.001).

CONCLUSION

Brief exposure to nystatin, amphotericin B, caspofungin, ketoconazole, fluconazole, and chlorhexidine enhances the antifungal effect of lysozyme and lactoferrin on C. dubliniensis isolates in vitro.

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.

Impact of brief exposure to antifungal agents on the post-antifungal effect and hemolysin activity of oral Candida albicans

Post-antifungal effect (PAFE) of Candida and its production of hemolysin are determinants of candidal pathogenicity. Candida albicans is the foremost aetiological agent of oral candidosis, which can be treated with polyene, azole, and echinocandin antifungals. However, once administered, the intraoral concentrations of these drugs tend to be subtherapeutic and transient due to the diluent effect of saliva and cleansing effect of the oral musculature. Hence, intra-orally, Candida may undergo a brief exposure to antifungal drugs.

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.

Postantifungal Effect of Micafungin against the Species Complexes of Candida albicans and Candida parapsilosis

Micafungin is an effective antifungal agent useful for the therapy of invasive candidiasis. Candida albicans is the most common cause of invasive candidiasis; however, infections due to non-C. albicans species, such as Candida parapsilosis, are rising. Killing and postantifungal effects (PAFE) are important factors in both dose interval choice and infection outcome. The aim of this study was to determinate the micafungin PAFE against 7 C. albicans strains, 5 Candida dubliniensis, 2 Candida Africana, 3 C. parapsilosis, 2 Candida metapsilosis and 2 Candida orthopsilosis. For PAFE studies, cells were exposed to micafungin for 1 h at concentrations ranging from 0.12 to 8 μg/ml. Time-kill experiments (TK) were conducted at the same concentrations. Samples were removed at each time point (0-48 h) and viable counts determined. Micafungin (2 μg/ml) was fungicidal (≥ 3 log₁₀ reduction) in TK against 5 out of 14 (36%) strains of C. albicans complex. In PAFE experiments, fungicidal endpoint was achieved against 2 out of 14 strains (14%). In TK against C. parapsilosis, 8 μg/ml of micafungin turned out to be fungicidal against 4 out 7 (57%) strains. Conversely, fungicidal endpoint was not achieved in PAFE studies. PAFE results for C. albicans complex (41.83 ± 2.18 h) differed from C. parapsilosis complex (8.07 ± 4.2 h) at the highest tested concentration of micafungin. In conclusion, micafungin showed significant differences in PAFE against C. albicans and C. parapsilosis complexes, being PAFE for the C. albicans complex longer than for the C. parapsilosis complex.

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.

Impact of brief and sequential exposure to nystatin, amphotericin B, ketoconazole, and fluconazole in modulating adhesion traits of oral Candida dubliniensis isolates

AIM

Candida adherence is implicated in the pathogenesis of oral candidosis. Adhesion to buccal epithelial cells (BEC), germ tube (GT) formation, and relative cell surface hydrophobicity (CSH) are colonization attributes of candidal pathogenicity. Candida dubliniensis (C. dubliniensis) is allied with recurrent oral candidosis, which can be treated with nystatin, amphotericin B, ketoconazole, and fluconazole. Due to the diluent effect of saliva and the cleansing effect of the oral musculature in the oral cavity C. dubliniensis isolates undergo brief and sequential exposure to antifungal agents during therapy. Thus, in the present study, we evaluated the adhesion to BEC, GT formation, and the CSH of oral isolates of C. dubliniensis following brief and sequential exposure to nystatin, amphotericin B, ketoconazole, and fluconazole.

METHODS

After determining the minimum inhibitory concentration (MIC) of the aforementioned drugs, 20 oral isolates of C. dubliniensis were briefly (1 h), and sequentially (10 days) exposed to subcidal concentrations of these drugs. Following drug removal, adhesion to BEC, GT formation, and CSH of these isolates were determined.

RESULTS

The percentage reduction of adhesion to BEC, GT formation, and CSH of the isolates following exposure to antifungal agents were as follows: nystatin: 53.55%, 33.98%, and 29.83% (P < 0.001); amphotericin B: 53.84%, 36.23%, and 28.97% (P < 0.001); ketoconazole: 37.43%, 20.51%, and 16.49% (P < 0.001); and fluconazole: 8.93% (P < 0.001), 1.6%, and 0.63% (P > 0.05).

CONCLUSIONS

Brief and sequential exposure of C. dubliniensis to antifungal agents would continue to wield an antifungal effect by altering its adhesion attributes, and elucidate possible pharmacodynamics by which antifungal agents might operate in modulating candidal adherence.