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Vasopressors are frequently given in hemodynamically unstable patients with severe Candida sepsis. While catecholamines can aggravate sepsis-induced immune dysfunction and modulate bacterial virulence traits, their impact on fungal pathogenicity is poorly understood. Using IncuCyte time-lapse microscopy and a fruit fly candidiasis model, we studied growth rates, morphogenesis, stress tolerance, and virulence of C. albicans cocultured with epinephrine and norepinephrine. We found that pharmacologically attainable catecholamine serum concentrations caused minimal changes to in vitro growth kinetics, filamentation, and fungal resistance to thermal or oxidative stress. Similarly, exposure of C. albicans to catecholamines did not alter the survival of infected flies. [ABSTRACT FROM AUTHOR]

Background. Azole-resistant aspergillosis in high-risk patients with hematological malignancy or hematopoietic stem cell transplantation (HSCT) is a cause of concern. Methods. We examined changes over time in triazole minimum inhibitory concentrations (MICs) of 290 sequential Aspergillus isolates recovered from respiratory sources during 1999-2002 (before introduction of the Aspergillus-potent triazoles voriconazole and posaconazole) and 2003-2015 at MD Anderson Cancer Center. We also tested for polymorphisms in ergosterol biosynthetic genes (cyp51A, erg3C, erg1) in the 37 Aspergillus fumigatus isolates isolated from both periods that had non-wild-type (WT) MICs. For the 107 patients with hematologic cancer and/or HSCT with invasive pulmonary aspergillosis, we correlated in vitro susceptibility with 42-day mortality. Results. Non-WT MICs were found in 37 (13%) isolates and was only low level (MIC <8 mg/L) in all isolates. Higher-triazole MICs were more frequent in the second period and were Aspergillus-species specific, and only encountered in A. fumigatus. No polymorphisms in cyp51A, erg3C, erg1 genes were identified. There was no correlation between in vitro MICs with 42-day mortality in patients with invasive pulmonary aspergillosis, irrespective of antifungal treatment. Asian race (odds ratio [OR], 20.9; 95% confidence interval [CI], 2.5-173.5; P = .005) and azole exposure in the prior 3 months (OR, 9.6; 95% CI, 1.9-48.5; P = .006) were associated with azole resistance. Conclusions. Non-WT azole MICs in Aspergillus are increasing and this is associated with prior azole exposure in patients with hematologic cancer or HSCT. However, no correlation of MIC with outcome of aspergillosis was found in our patient cohort. [ABSTRACT FROM AUTHOR]

Background Efficient animal models are needed in order to investigate fungal pathogenicity and antifungal therapy in the context of epithelial injury, e.g. due to anticancer chemotherapy. Using a Gal4 enhancer trap (GET) zebrafish line facilitating metronidazole (MTZ)-inducible ablation of epithelial (periderm) cells, we aimed to establish a mucositis model predisposing larvae for fungal invasion. Methods 4 days post-fertilization Et(Gal4-VP16)zc1044A;Tg(UAS-1b:nfsB-mCherry)c264 zebrafish larvae were exposed to 10 mM MTZ in E3 medium for 5 h. After washing, larvae were incubated in Candida albicans or Rhizopus arrhizus spore suspensions (5 × 105–5 × 107/mL) for 16 h. Thereafter, larvae were washed again and survival was monitored until 72 h post-infection. Fungal burden was assessed by 18S qPCR and histopathology. For drug protection studies, 5 µg/mL amphotericin B (AMB) or posaconazole (PCZ) was added to the medium of R. arrhizus -infected larvae at 16 h post-infection. Results In MTZ-treated GET larvae, inoculum-dependent mortality was found for both R. arrhizus (panel A) and C. albicans (panel B). High inter-experiment reproducibility of survival rates was seen (CV < 0.3). Using a GFP-expressing R. arrhizus strain, fungal invasion of the larval tissue was verified by fluorescence microscopy (panel C). PCZ and AMB improved survival rates of R. arrhizus -infected (5 × 106/mL) larvae from 46% to 85% and 51% to 86%, respectively (P < 0.001). Similarly, significantly reduced fungal burden in AMB and PCZ-treated larvae was documented by qPCR (panel D) and histopathology. In additional validation experiments, the hypo-virulent phenotypes of a CotH-depleted R. arrhizus strain and filamentation-defective C. albicans mutants (Δefg1 and Δcph1) were recapitulated in zebrafish larvae with epithelial cell loss. Conclusion We have established a robust and reliable model of invasive mycoses by controlled ablation of epithelial cells in zebrafish larvae, allowing for rapid immersion-based interrogation of different infection and treatment options. Our proof-of-concept experiments suggest that GET zebrafish larvae are positioned as an appealing high-throughput in vivo system for antifungal drug screening or comparative virulence studies. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

While mammalian models remain the gold standard to study invasive mycoses, mini-host invertebrate models have provided complementary platforms for explorative investigations of fungal pathogenesis, host-pathogen interplay, and antifungal therapy. Specifically, our group has established Toll-deficient Drosophila melanogaster flies as a facile and cost-effective model organism to study candidiasis, and we have recently expanded these studies to the emerging and frequently multidrug-resistant yeast pathogen Candida auris. Our proof-of-concept data suggest that fruit flies could hold a great promise for large-scale applications in antifungal drug discovery and the screening of C. auris (mutant) libraries with disparate pathogenic capacity. This chapter discusses the advantages and limitations of D. melanogaster to study C. auris candidiasis and provides a step-by-step guide for establishing and troubleshooting C. auris infection and antifungal treatment of Toll-deficient flies along with essential downstream readouts., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)