Pharmacokinetic–pharmacodynamic optimization of triazole antifungal therapy:

Fungal Diseases in Elasmobranchs and Their Possible Treatment with a Special Mention to Azole Antifungal Agents

INTRODUCTION

Elasmobranchs currently constitute an important part of the animal collection of many aquariums worldwide. Their maintenance under human care has allowed us to describe and identify new pathogens and diseases affecting them, as well as to determine different treatments for these diseases. Great advances in elasmobranch husbandry have been developed.

METHODS

A search was performed on scientific databases as PubMed and other specialized sources (IAAAM archive).

RESULTS

Little information on pharmacotherapeutics is available in this taxonomic group, and treatments lack a scientific base and instead are frequently dependent on empirical knowledge. Pharmacokinetic studies are the first step to determining therapeutic protocols that are safe and effective. The available bibliography shows that a majority of the mycoses recorded in cartilaginous fish are severe, aggravated by the fact that the antifungal treatments administered, following the guidelines used for teleost species, are ineffective in elasmobranchs. Azoles appear to be a promising group of antifungals for use in treating systemic mycoses in sharks and rays.

CONCLUSIONS

Based on the findings of this review, it is essential to investigate the pharmacokinetics of the different antifungals in these species in order to provide therapeutic options for fungal infections in cartilaginous fish.

Alterations in the gut bacterial microbiome in fungal Keratitis patients

Dysbiosis in the gut microbiome has been implicated in several diseases including auto-immune diseases, inflammatory diseases, cancers and mental disorders. Keratitis is an inflammatory disease of the eye significantly contributing to corneal blindness in the developing world. It would be worthwhile to investigate the possibility of dysbiosis in the gut microbiome being associated with Keratitis. Here, we have analyzed fungal and bacterial populations in stool samples through high-throughput sequencing of the ITS2 region for fungi and V3-V4 region of 16S rRNA gene for bacteria in healthy controls (HC, n = 31) and patients with fungal keratitis (FK, n = 32). Candida albicans (2 OTUs), Aspergillus (1 OTU) and 3 other denovo-OTUs were enriched in FK samples and an unclassified denovo-OTU was enriched in HC samples. However, the overall abundances of these ‘discriminatory’ OTUs were very low (< 0.001%) and not indicative of significant dysbiosis in the fungal community inhabiting the gut of FK patients. In contrast, the gut bacterial richness and diversity in FK patients was significantly decreased when compared to HC. 52 OTUs were significantly enriched in HC samples whereas only 5 OTUs in FK. The OTUs prominently enriched in HC were identified as Faecalibacterium prausnitzii, Bifidobacterium adolescentis, Lachnospira, Mitsuokella multacida, Bacteroides plebeius, Megasphaera and Lachnospiraceae. In FK samples, 5 OTUs affiliated to Bacteroides fragilis, Dorea, Treponema, Fusobacteriaceae, and Acidimicrobiales were significantly higher in abundance. The functional implications are that Faecalibacterium prausnitzii, an anti-inflammatory bacterium and Megasphaera, Mitsuokella multacida and Lachnospira are butyrate producers, which were enriched in HC patients, whereas Treponema and Bacteroides fragilis, which are pathogenic were abundant in FK patients, playing a potential pro-inflammatory role. Heatmap, PCoA plots and functional profiles further confirm the distinct patterns of gut bacterial composition in FK and HC samples. Our study demonstrates dysbiosis in the gut bacterial microbiomes of FK patients compared to HC. Further, based on inferred functions, it appears that dysbiosis in the gut of FK subjects is strongly associated with the disease phenotype with decrease in abundance of beneficial bacteria and increase in abundance of pro-inflammatory and pathogenic bacteria.

Impact of Mucositis on Absorption and Systemic Drug Exposure of Isavuconazole

Isavuconazonium sulfate is the water-soluble prodrug of isavuconazole. Population analyses have demonstrated relatively predictable pharmacokinetic (PK) behavior in diverse patient populations. We evaluated the impact of mucositis on the oral isavuconazole exposure using population PK modeling. This study included patients treated in two phase 3 trials of isavuconazole, SECURE for treatment of invasive aspergillosis (IA) and other filamentous fungi and VITAL for patients with mucormycosis, invasive fungal disease (IFD) caused by other rare fungi, or IA and renal impairment. Mucositis was reported by site investigators and its impact on oral bioavailability was assessed. Use of the oral formulation was at the discretion of the investigator. Patients with plasma samples collected during the use of isavuconazonium sulfate were included in the construction of population PK model. Of 250 patients included, 56 patients had mucositis at therapy onset or as an adverse event during oral isavuconazole therapy. Levels of oral bioavailability were comparable, at 98.3% and 99.8%, respectively. The average drug exposures (average area under the curve [AUC_ave]) calculated from either the mean or median parameter estimates were not different between patients with and without mucositis. Mortality and overall clinical responses were similar between patients receiving oral therapy with and without mucositis. We found that isavuconazole exposures and clinical outcomes in this subset of patients with mucositis who were able to take oral isavuconazonium sulfate were comparable to those in patients without mucositis, despite the difference in oral bioavailability. Therefore, mucositis may not preclude use of the oral formulation of isavuconazonium sulfate.