The post-antifungal effect (PAFE) of amphotericin B, nystatin, ketoconazole and 5-fluorocytosine and its impact on the colonization traits of Candida glabrata

Reviving the interest in the versatile drug nystatin: A multitude of strategies to increase its potential as an effective and safe antifungal agent

Nystatin is an antifungal molecule with a remarkable yet squandered versatility. In this review, its mechanism of action is explored, along with its extensive action spectrum and toxicity. A multitude of methodologies to tackle the drug's physical and chemical hurdles are outlined along with some proven-effective strategies to increase its activity and/or decrease its toxicity. A separate detailed section focused on micro and nanotechnology solutions addresses new drug delivery systems made of polymeric, metallic or lipid materials. Although the topical route depicts greater representativeness amongst these formulations, the intravenous, dental, oral, vaginal and inhalation routes are also mentioned. The unsuccessful previous attempts at developing parenteral formulations of nystatin or even the withdrawal of a nystatin-loaded multilamellar liposome should not divert research away from this drug. In fact, the interest in nystatin ought to be reawakened with the ongoing clinical trials on the promising nystatin-like genetically engineered derivate BSG005.

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.

Postantifungal-like effect of sublethal treatment of Candida albicans with acid-electrolyzed water

OBJECTIVE

Acid-electrolyzed water (AEW) has been applied to the treatment of oral candidiasis. We evaluated the postantifungal effect (PAFE)-like activity of AEW against Candida albicans under sublethal conditions by exposing C. albicans to dilute AEW.

DESIGN

The growth of C. albicans after a short-term exposure to dilute AEW was evaluated in broth and on agar culture. The involvement of reactive oxygen species (ROS) in the PAFE was examined by flow cytometric analysis with hydroxyphenyl fluorescein (HPF) as a fluorescence probe.

RESULTS

The dilute AEW exerted PAFE-like activity against C. albicans. ROS were produced in the cells treated with AEW diluted 16 times or fewer. The increase in HPF fluorescence after treatment with dilute AEW was cancelled by dimethyl sulfoxide, a hydroxyl radical (OH) scavenger.

CONCLUSION

It would be expected that the ROS, especially OH, produced in the C. albicans cells treated with sublethal dilutions of AEW could exert PAFE-like activity against the fungal cells.

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

OBJECTIVE

The aim of this investigation was to measure the postantifungal effect (PAFE) of 6 different oral Candida species following exposure to amphotericin B.

MATERIALS AND METHODS

Five oral isolates each of Candida albicans, Candida tropicalis, Candida krusei, Candida parapsilosis, Candida glabrata and Candida guilliermondii (total of 30 isolates) were examined for the presence of PAFE after 1 h of exposure to the minimum inhibitory concentration of amphotericin B. The PAFE was determined as the difference in time (hours) required for the growth of the drug-free control and the drug-exposed test cultures to increase to 0.05 absorbance level following removal of amphotericin B.

RESULTS

The mean duration of amphotericin B-induced PAFE was lowest for C. albicans (5.91 ± 0.31 h) and greatest for C. parapsilosis (12.72 ± 0.11 h), while C. guilliermondii (8.32 ± 0.33 h), C. glabrata (8.43 ± 0.21 h), C. krusei (9.68 ± 0.23 h) and C. tropicalis (10.98 ± 0.18 h) elicited intermediate values.

CONCLUSION

Even a limited exposure to sublethal concentrations of amphotericin B suppressed growth of Candida species of oral origin. The significant variation in amphotericin B-induced PAFE amongst different Candida species may have clinical implications in terms of amphotericin B regimens used in the management of oral candidiasis.