Disseminated cryptococcosis is a rare but serious opportunistic infection following solid organ transplantation and rarely occurs within the first month of transplantation. We report a case of disseminated Cryptococcus neoformans infection occurring 14 days after orthotopic heart transplantation which required mechanical circulatory support with venoarterial extracorporeal membrane oxygenation (VA-ECMO). Management was complicated by alterations in antifungal pharmacokinetics and the inability to perform serial lumbar punctures while anticoagulated. Antifungal therapy with nonliposomal amphotericin B, flucytosine, and fluconazole was administered. A combination of optic nerve sheath diameter measurements, CT scans, and evaluation for papilledema was used as temporizing, noninvasive surrogates for intracranial pressure monitoring until lumbar punctures could be safely performed. The patient was successfully decannulated, weaned from mechanical support, and discharged from the intensive care unit.

Flucytosine-induced colitis is exceedingly rare with very few cases reported in the literature. We present a case of a 56-year-old male with history of ulcerative colitis and seronegative spondyloarthropathy who developed abdominal pain, diarrhoea and rectal bleeding following commencement of flucytosine and amphotericin B for cryptococcal empyema. The clinical features and biochemistry initially raised concern for an ulcerative colitis flare. Histopathology demonstrated features of an acute colitis. Subsequent cessation of flucytosine without alteration to management of his underlying ulcerative colitis led to a rapid and complete resolution of symptoms, supporting a diagnosis of flucytosine-induced colitis. This case highlights the importance of considering a drug-induced colitis in patients with inflammatory bowel disease presenting with new or worsening gastrointestinal symptoms. Accurate differentiation from disease flare is essential to avoid unnecessary changes or escalation in immunosuppressive therapy.

Purpureocillium lilacinum, a common environmental fungus, can cause hyalohyphomycosis with varied clinical manifestations. Mortality rates can reach 20% with invasive disease. P. lilacinum is intrinsically resistant to amphotericin B, leaving few treatment options. In the absence of clinical breakpoints, epidemiological cutoff values (ECVs) can aid clinicians in monitoring antifungal resistance trends and in guiding initial therapy. We performed antifungal susceptibility testing (AFST) on P. lilacinum isolates to establish minimum inhibitory concentration (MIC) and minimum effective concentration (MEC) distributions and ECVs. Data were collected from 13 laboratories located in seven countries. AFST was performed by broth microdilution (CLSI M38 standard) for itraconazole, voriconazole, posaconazole, isavuconazole, terbinafine, flucytosine, amphotericin B, natamycin, and manogepix. ECVs were established using the iterative statistical method with ECOFFinder (v2.1) following CLSI M57 guidelines. Results from 479 P. lilacinum isolates were analyzed. ECVs were 1 μg/mL for voriconazole, 2 μg/mL for posaconazole, 4 μg/mL for isavuconazole, and 2 μg/mL for terbinafine. Itraconazole displayed a trimodal MIC distribution, although almost all MICs were ≥0.5 µg/mL (mode, 16 μg/mL). Amphotericin B, natamycin, and flucytosine MICs were truncated at the high end of the range and consistent with intrinsic resistance. The manogepix modal MEC was 0.008 μg/mL. These proposed P. lilacinum ECVs and MIC/MEC distributions provide baseline data to monitor resistance trends. Our results confirm that P. lilacinum is intrinsically resistant (IR) to amphotericin B and likely IR to natamycin and flucytosine. Caution is needed in interpreting itraconazole results due to high interlaboratory variability.IMPORTANCEPurpureocillium lilacinum is a hyaline mold commonly found in the environment and used as an agricultural biopesticide. Infections caused by P. lilacinum can range from fungal eye infections to life-threatening pulmonary and disseminated disease, and mortality rates can be high (up to 20%). Single-center studies examining antifungal susceptibility testing (AFST) data found reduced susceptibility to certain antifungals, but more robust global AFST studies are needed to help interpret MICs and MECs. We performed AFST according to the Clinical Laboratory and Standards Institute reference method in thirteen independent laboratories on 479 P. lilacinum isolates to establish MIC/MEC distributions and epidemiological cutoff values (ECVs) for nine antifungals, including those recommended by global treatment guidelines. The calculated ECVs were 1 μg/mL for voriconazole, 2 μg/mL for posaconazole, 4 μg/mL for isavuconazole, and 2 μg/mL for terbinafine. Our results also confirm that P. lilacinum is intrinsically resistant to amphotericin B and likely intrinsically resistant to natamycin and flucytosine. Caution is needed in interpreting itraconazole AFST results due to high interlaboratory variability. These antifungal in vitro susceptibility data suggest limited options to treat P. lilacinum infections.

Cryptococcosis is a major health threat among immunocompromised individuals, resulting in life-threatening consequences secondary to brain invasion. The limited treatment options and the increased incidence of treatment failure and relapses urge the need for more effective therapies. In this study, we investigated the therapeutic potential of nitroxoline (NTX) in treating cryptococcal infection. NTX exhibited potent fungicidal activity against Cryptococcus neoformans/gattii clinical isolates, with an MIC90 of 1 µg/mL. In addition, NTX substantially inhibits the main virulence traits of cryptococcal cells, including the polysaccharide capsule, melanin production, and the urease enzyme, which are crucial for the infection progression. In exploring the potential mechanism of action, our results revealed the relationship between the metal-chelating properties of the NTX scaffold and its antifungal activity. Interfering metal chelation, either through structural modification or exogenous supplementation with varied divalent cations, significantly reduced the antifungal and anti-virulence activities of NTX. Given its potential therapeutic role, we evaluated the interaction between NTX and the clinically used antifungals amphotericin B, flucytosine and fluconazole. Additionally, we investigated the tendency of cryptococcal cells to develop resistance following repeated exposure to NTX, as well as its efficacy in the Caenorhabditis elegans nematode model of cryptococcal infection. Notably, cryptococcal cells exhibited consistent susceptibility to NTX upon repeated exposure to a subinhibitory concentration. In the C. elegans model, NTX significantly reduced the fungal burden of the infected worms, achieving a 2-log10 reduction, and consistently enhanced their survival compared to untreated group. These findings highlight the potential role of the NTX scaffold in combating cryptococcal infection that warrants further investigation.

Castration-resistant prostate cancer (CRPC) is characterised by persistent androgen receptor (AR)-axis activity, therapy-driven resistance, and limited durability of available systemic treatments. Tumour-tropic mesenchymal stem/stromal cells (MSCs), including adipose-derived MSCs (ADSCs), have emerged as promising vehicles for targeted gene therapeutics. This review synthesises our three experimental studies examining stem cell-delivered gene-directed enzyme prodrug therapy (GDEPT) using cytosine deaminase (CD)/5-fluorocytosine (5-FC) and secreted TRAIL in CRPC xenograft models. We performed a comparative analysis of three studies in which hTERT-immortalised human ADSCs were engineered via lentiviral vectors to deliver CD alone, secreted TRAIL alone, or CD+TRAIL in combination, and were administered by intracardiac injection into male nude mice bearing PC3 xenografts. In vitro conversion efficiency, cell viability, apoptosis markers, and in vivo tumour volume endpoints were compared across studies. All three therapeutic platforms demonstrated measurable tumour growth inhibition relative to controls. The CD+TRAIL combination achieved the greatest in vivo efficacy (tumours approximately 26% of control at day 14), compared with CD alone (approximately 71%) or TRAIL paired with irinotecan. Enzymatic conversion of 5-FC to 5-FU exceeded 93% in conditioned medium. Primary translational risks include thrombotic events associated with systemic MSC dosing, tumourigenicity and genotoxicity of hTERT-immortalised, integrating-vector-engineered cells, immunogenicity of xenogeneic CD enzyme, and systemic 5-fluorouracil leakage from flucytosine metabolism. Stem cell-delivered CD/5-FC and TRAIL constitutes a biologically rational, modular strategy for local cytotoxicity and resistance circumvention in CRPC. Successful clinical translation will require resolution of delivery-route feasibility, thrombosis risk mitigation, and a rigorous investigational new drug (IND)-enabling safety package.

Emphysematous pyelonephritis (EPN) is a severe, necrotizing infection that can affect the renal parenchyma, collecting system, or perinephric tissue. Although typically caused by enteric Gram-negative bacteria, infections secondary to Candida occur rarely. We present the case of a 72-year-old female who was transferred from an outside hospital with a chief complaint of abdominal pain in the setting of dislodged percutaneous nephrostomy tube for chronic hydronephrosis. Clinically, she presented without evidence of septic shock but was found to have elevated creatinine (6.04), concerning for acute renal failure. Urology was consulted and performed cystoscopy that showed a large bilateral mass consistent with fungal ball formation. Subsequent urine cultures speciated Candida tropicalis and Candida glabrata. Per infectious disease recommendations, the patient was initially started on treatment with fluconazole and flucytosine; however, fluconazole was switched to amphotericin B deoxycholate after sensitivities reported resistance to fluconazole for Candida tropicalis. Additionally, urology performed a bilateral percutaneous nephroscopy with ultrasonic lithotripsy for removal of her fungal bezoar on Day 22 of her hospitalization with subsequent nephrostograms that showed a patent genitourinary system. This case demonstrates successful treatment of EPN secondary to azole-resistant Candida species using combined systemic antifungal therapy and an endourologic approach. This avoided the use of percutaneous nephrostomy irrigation with amphotericin deoxycholate as recommended in current guidelines and prevented potential complications this procedure carries.

Fungal infections remain a major global health challenge, particularly among immunocompromised patients, with increasing morbidity and mortality driven by invasive candidiasis, aspergillosis, cryptococcosis, and emerging multidrug-resistant pathogens such as Candida auris. Although conventional antifungal classes, including azoles, echinocandins, polyenes, and flucytosine, remain central to antifungal therapy, their clinical utility is limited by toxicity, drug-drug interactions, restricted spectra, variable pharmacokinetics, and the growing emergence of antifungal resistance. These limitations have highlighted the urgent need for novel antifungal agents with improved safety profiles, new mechanisms of action, broader or more targeted activity, and optimized pharmacokinetic properties. This narrative review summarizes the current landscape of emerging antifungal therapies, focusing on ibrexafungerp 1, rezafungin 2, fosmanogepix 3, olorofim 4, opelconazole 5, and oteseconazole 6. Their mechanisms of action, antifungal spectra, resistance profiles, preclinical evidence, clinical development, pharmacokinetic advantages, and safety data are discussed and compared with established antifungal classes. Several of these agents introduce entirely novel antifungal targets, including inhibition of fungal dihydroorotate dehydrogenase and Gwt1-mediated glycosylphosphatidylinositol-anchor biosynthesis, while others optimize existing antifungal strategies through prolonged half-life, improved fungal selectivity, oral bioavailability, or inhaled pulmonary delivery. Collectively, these emerging antifungal agents expand therapeutic options against resistant Candida species, azole-resistant Aspergillus fumigatus (A.fumigatus), and difficult-to-treat molds, while potentially improving tolerability and reducing interaction-related limitations. However, important challenges remain, including limited activity against Mucorales for several agents, the potential emergence of future resistance, and the need for additional comparative clinical data and real-world experience. Overall, the expanding antifungal pipeline represents a major advancement toward more targeted and individualized antifungal therapy and may significantly reshape the future management of invasive and refractory fungal infections.

Mutations in gene regulatory regions have been shown to play a role in rapid adaptation, but the factors determining their contribution are largely unknown. Here, using the metabolic enzyme cytosine deaminase of budding yeast, we examine whether adaptation to 5-fluorocytosine, which requires reduced cytosine deamination and can readily arise from amino acid substitutions, may be reached by single promoter mutations. We generated all single-nucleotide substitutions and indels in the FCY1 promoter and assayed the resulting mutants in presence of 5-fluorocytosine. This revealed that no promoter mutation is sufficient for adaptation to occur. We next investigated how this inaccessibility of adaptation arises by combining large-scale expression measurements with the experimental characterization of the corresponding expression-fitness function. These experiments showed that the shape of this function precludes single promoter mutations from being adaptive. Although 24% of mutations significantly affect expression, the fitness curve is flat around wild-type level. As such, adaptation can only emerge from a severe reduction of expression, which cannot occur from a single mutation in the promoter. Our results show that the contribution of regulatory mutations to rapid adaptation depends not only on the distribution of mutational effect sizes on expression level but also on the shape of the function linking fitness to expression levels.

Magnusiomyces clavatus, formerly Saprochaete clavata or Geotrichum clavatum, is an ascomycetous yeast found in the environment as well as the gastrointestinal and respiratory tracts of humans. It has been described as an emerging, albeit rare, cause of invasive fungal disease affecting immunocompromised patients. Intrinsic resistance to fluconazole and echinocandins has been theorized; however, little else is known regarding optimal treatment regimens for this opportunistic pathogen. To our knowledge, only 13 infectious cases have been described in pediatric patients, all of which utilized a combination of antifungals including liposomal amphotericin B (LAmB) and voriconazole with or without flucytosine (5-FC). Here we report a case of a 4-year-old, 12.3 kg, female patient who immigrated from Ukraine and was admitted to our institution for an allogeneic umbilical cord blood transplant in the setting of bone marrow failure secondary to Fanconi anemia. On day +6 after cell transplantation, the patient developed febrile neutropenia found to be because of invasive M. clavatus fungemia on day +7. The patient was empirically treated with LAmB, micafungin, and posaconazole (POS), the latter of which failed to reach therapeutic levels. Ultimately, our patient defervesced and cleared blood cultures after transitioning LAmB to 5-FC, followed by definitive treatment with isavuconazole (ISA) monotherapy. To our knowledge, this is the first case of pediatric M. clavatus ultimately treated with 5-FC plus POS followed by ISA alone.