sirolimus and Mucormycosis

We describe the first successful case of posaconazole salvage therapy for mucormycosis with concomitant sirolimus (SRL) maintenance immunosuppression following liver transplantation, despite black box drug interaction following intolerance to first-line tacrolimus and amphotericin due to nephrotoxicity and neurotoxicity. This case describes a 55-year-old female who developed rhinocerebral mucormycosis 108 days after liver transplantation. After 3 months of posaconazole therapy, the patient remains free of disease at 3 years posttransplant. This case report illustrates successful resolution of mucormycosis without SRL toxicity to resolve nephrotoxicity of long-term amphotericin on top of already nephrotoxic immunosuppression. With higher bioavailability of recently FDA-approved posaconazole delayed release tablets, this azole may be a therapeutic option for transplant patients who need to remain on CYP3A4-metabolized immunosuppressive agents.

Topics: Antifungal Agents; Female; Humans; Immunosuppressive Agents; Liver Transplantation; Maintenance Chemotherapy; Middle Aged; Mucormycosis; Salvage Therapy; Sirolimus; Treatment Outcome; Triazoles

The environmentally ubiquitous fungus

Topics: Animals; Antifungal Agents; Disease Models, Animal; Drug Resistance, Fungal; Epigenesis, Genetic; Humans; Male; Mice; Mice, Inbred BALB C; Mucor; Mucormycosis; RNA Interference; Sirolimus; Tacrolimus

Mucormycosis-an emergent, deadly fungal infection-is difficult to treat, in part because the causative species demonstrate broad clinical antifungal resistance. However, the mechanisms underlying drug resistance in these infections remain poorly understood. Our previous work demonstrated that one major agent of mucormycosis, Mucor circinelloides, can develop resistance to the antifungal agents FK506 and rapamycin through a novel, transient RNA interference-dependent mechanism known as epimutation. Epimutations silence the drug target gene and are selected by drug exposure; the target gene is re-expressed and sensitivity is restored following passage without drug. This silencing process involves generation of small RNA (sRNA) against the target gene via core RNAi pathway proteins. To further elucidate the role of epimutation in the broad antifungal resistance of Mucor, epimutants were isolated that confer resistance to another antifungal agent, 5-fluoroorotic acid (5-FOA). We identified epimutant strains that exhibit resistance to 5-FOA without mutations in PyrF or PyrG, enzymes which convert 5-FOA into the active toxic form. Using sRNA hybridization as well as sRNA library analysis, we demonstrate that these epimutants harbor sRNA against either pyrF or pyrG, and further show that this sRNA is lost after reversion to drug sensitivity. We conclude that epimutation is a mechanism capable of targeting multiple genes, enabling Mucor to develop resistance to a variety of antifungal agents. Elucidation of the role of RNAi in epimutation affords a fuller understanding of mucormycosis. Furthermore, it improves our understanding of fungal pathogenesis and adaptation to stresses, including the evolution of drug resistance.

Topics: Antifungal Agents; Drug Resistance, Multiple, Fungal; Epigenesis, Genetic; Genes, Fungal; Humans; Mucor; Mucormycosis; Mutation; Orotate Phosphoribosyltransferase; Orotic Acid; Orotidine-5'-Phosphate Decarboxylase; RNA Interference; RNA, Fungal; Sirolimus; Tacrolimus

To evaluate the in vitro interactions of isavuconazole with immune suppressors (tacrolimus, cyclosporin A or sirolimus) against 30 Mucorales isolates belonging to the most common species responsible for mucormycosis in humans (Rhizopus arrhizus, Rhizopus delemar, Rhizopus microsporus, Lichtheimia corymbifera, Lichtheimia ramosa, Mucor circinelloides and Rhizomucor pusillus).. In vitro interaction was evaluated by a microdilution chequerboard technique.. Combination of isavuconazole with tacrolimus, cyclosporin A or sirolimus, was synergistic for 50%, 46% and 7% of the isolates, respectively. Antagonistic interaction was observed for 4% of the isolates for the combination with cyclosporin A (one R. arrhizus isolate) and for 32% of the isolates for the combination with sirolimus (six R. arrhizus isolates and three R. pusillus isolates).. These in vitro data show that calcineurin inhibitors are more likely than inhibitors of the mTOR pathway to enhance the activity of isavuconazole against Mucorales. These in vitro results warrant further animal experiments.

Topics: Antifungal Agents; Cyclosporine; Immunosuppressive Agents; Microbial Sensitivity Tests; Mucorales; Mucormycosis; Nitriles; Pyridines; Sirolimus; Tacrolimus; Triazoles

Mucormycosis is a rare but refractory mycosis with high mortality. Few therapeutic options are available and novel strategies are needed. Calcineurin inhibitors are known to have antifungal activity, including synergy with various antifungals. We examined the interaction of caspofungin with calcineurin inhibitors and sirolimus against Glomeromycetes.. Twenty-six strains of Glomeromycetes representing seven species (Rhizopus arrhizus, Rhizopus microsporus, Mucor sp., Rhizomucor pusillus, Cunninghamella berthollettiae, Mycocladus corymbifera and Apophysomyces elegans) were studied. Antifungal susceptibility testing was performed according to CLSI M38-A2, modified for chequerboard dilution testing using the minimum effective concentration (MEC) endpoint for caspofungin and calcineurin inhibitors/sirolimus. Synergy was defined as a fractional inhibitory concentration index ≤0.5, indifference >0.5 to ≤4.0 and antagonism >4.0.. Caspofungin had no intrinsic activity against Glomeromycetes (MEC >8 mg/L). The combination of caspofungin with calcineurin inhibitors and sirolimus showed synergy in seven isolates. In the presence of calcineurin inhibitors and sirolimus, the MEC of caspofungin was significantly lowered (>4-fold) in 24 and 7 isolates, respectively. All species showed lower MECs of caspofungin with calcineurin inhibitors and only R. arrhizus, Mucor sp. and R. pusillus showed lower MECs with sirolimus. No antagonism was observed.. Calcineurin inhibitors and sirolimus significantly lowered MECs of caspofungin for Glomeromycetes, with occasional synergy observed. The clinical significance of this should be further investigated.

Topics: Antifungal Agents; Calcineurin Inhibitors; Caspofungin; Drug Interactions; Drug Resistance, Multiple, Fungal; Drug Synergism; Echinocandins; Glomeromycota; Humans; Immunosuppressive Agents; Lipopeptides; Microbial Sensitivity Tests; Mucorales; Mucormycosis; Sirolimus