Model Of Invasive Candidiasis Research Articles

Candida albicans cDNA library screening reveals novel potential diagnostic targets for invasive candidiasis

The detection of patterns associated with the invasive form of Candida albicans, such as Candida albicans germ tube antibodies (CAGTA), is a useful complement to blood culture for Invasive Candidiasis (IC) diagnosis. As CAGTA are detected by a non-standardisable and non-automatable technique, a Candida albicans cDNA expression library was screened with CAGTA isolated from serum of an animal model of invasive candidiasis, and five protein targets were identified: hyphally regulated cell wall protein 1 (Hyr1), enolase 1 (Eno1), coatomer subunit gamma (Sec21), a metallo-aminopeptidase (Ape2) and cystathionine gamma-lyase (Cys3). Homology with proteins from other organisms rules out Cys3 as a good biomarker while Sec21 results suggest that it is not in the germ tubes surface but secreted to the external environment. Our analysis propose Ape2, Sec21 and a region of Hyr1 different from the one currently being studied for immunoprotection as potential biomarker candidates for the diagnosis of IC.

Antifungal activity of ruthenium (II) complex combined with fluconazole against drug-resistant Candida albicans in vitro and its anti-invasive infection in vivo

With the abuse of antibiotics and azoles, drug-resistant Candida albicans infections have increased sharply and are spreading rapidly, thereby significantly reducing the antifungal efficacy of existing therapeutics. Several patients die of fungal infections every year. Therefore, there is an urgent requirement to develop new drugs. Accordingly, we synthesized a series of polypyridyl ruthenium (II) complexes having the formula [Ru (NN)2 (bpm)] (PF6)2 (N-N = 2,2′-bipyridine) (bpy, in Ru1), 1,10-phenanthroline (phen, in Ru2), 4,7-diphenyl-1,10-phenanthroline (DIP, in Ru3) (bpm = 2,2′-bipyrimidine) and studied their antifungal activities. Ru3 alone had no effect on the drug-resistant strains, but Ru3 combined with fluconazole (FLC) exhibited significant antifungal activity on drug-resistant strains. A high-dose combination of Ru3 and FLC exhibited direct fungicidal activity by promoting the accumulation of reactive oxygen species and damaging the cellular structure of C. albicans. Additionally, the combination of Ru3 and FLC demonstrated potent antifungal efficacy in vivo in a mouse model of invasive candidiasis. Moreover, the combination significantly improved the survival state of mice, restored their immune systems, and reduced renal injury. These findings could provide ideas for the development of ruthenium (II) complexes as novel antifungal agents for drug-resistant microbial stains.

The regulatory subunits of CK2 complex mediate DNA damage response and virulence in Candida Glabrata

BackgroundCandida glabrata which belongs to normal microbiota, has caused significant concern worldwide due to its high prevalence and drug resistance in recent years. C. glabrata has developed many strategies to evade the clearance of the host immune system, thereby causing persistent infection. Although coping with the induced DNA damage is widely acknowledged to be important, the underlying mechanisms remain unclear.ResultsThe present study provides hitherto undocumented evidence of the importance of the regulatory subunits of CgCK2 (CgCkb1 and CgCkb2) in response to DNA damage. Deletion of CgCKB1 or CgCKB2 enhanced cellular apoptosis and DNA breaks and led to cell cycle delay. In addition, deficiencies in survival upon phagocytosis were observed in Δckb1 and Δckb2 strains. Consistently, disruption of CgCKB1 and CgCKB2 attenuated the virulence of C. glabrata in mouse models of invasive candidiasis. Furthermore, global transcriptional profiling analysis revealed that CgCkb1 and CgCkb2 participate in cell cycle resumption and genomic stability.ConclusionsOverall, our findings suggest that the response to DNA damage stress is crucial for C. glabrata to survive in macrophages, leading to full virulence in vivo. The significance of this work lies in providing a better understanding of pathogenicity in C. glabrata-related candidiasis and expanding ideas for clinical therapies.

Synergy In Vitro of Nikkomycin Z with Azole Against the Invasive Form of Candida albicans.

In a previous study, therapeutic activity of nikkomycin Z (NZ) in a model of invasive candidiasis did not appear to correlate with lesser activity in vitro (using classical MIC methods) with planktonic organisms. However, NZ potency was much greater assaying activity in vitro against germ tubes, the initiator of the invasive mycelial form of the fungus, as occurs in infected tissues. Synergy has been demonstrated for NZ and other drugs, notably fluconazole (the most commonly used drug against candidiasis), in planktonic testing, which correlated with results in vivo. This raised the question whether activity shown by NZ alone against germ tubes would be reflected in drug combinations, and even whether synergy testing against germ tubes might be a better correlate of synergy in future in vivo studies. We show in this study significant NZ synergy with fluconazole against germ tubes, for several C. albicans isolates, with testing in many drug ratios. This observation opens the way for further explorations of this method of susceptibility testing for synergy, and correlation with combination therapy against candidiasis.

Cdc14 phosphatase contributes to cell wall integrity and pathogenesis in Candida albicans.

The Cdc14 phosphatase family is highly conserved in fungi. In Saccharomyces cerevisiae, Cdc14 is essential for down-regulation of cyclin-dependent kinase activity at mitotic exit. However, this essential function is not broadly conserved and requires only a small fraction of normal Cdc14 activity. Here, we identified an invariant motif in the disordered C-terminal tail of fungal Cdc14 enzymes that is required for full enzyme activity. Mutation of this motif reduced Cdc14 catalytic rate and provided a tool for studying the biological significance of high Cdc14 activity. A S. cerevisiae strain expressing the reduced-activity hypomorphic mutant allele (cdc14hm ) as the sole source of Cdc14 proliferated like the wild-type parent strain but exhibited an unexpected sensitivity to cell wall stresses, including chitin-binding compounds and echinocandin antifungal drugs. Sensitivity to echinocandins was also observed in Schizosaccharomyces pombe and Candida albicans strains lacking CDC14, suggesting this phenotype reflects a novel and conserved function of Cdc14 orthologs in mediating fungal cell wall integrity. In C. albicans, the orthologous cdc14hm allele was sufficient to elicit echinocandin hypersensitivity and perturb cell wall integrity signaling. It also caused striking abnormalities in septum structure and the same cell separation and hyphal differentiation defects previously observed with cdc14 gene deletions. Since hyphal differentiation is important for C. albicans pathogenesis, we assessed the effect of reduced Cdc14 activity on virulence in Galleria mellonella and mouse models of invasive candidiasis. Partial reduction in Cdc14 activity via cdc14hm mutation severely impaired C. albicans virulence in both assays. Our results reveal that high Cdc14 activity is important for C. albicans cell wall integrity and pathogenesis and suggest that Cdc14 may be worth future exploration as an antifungal drug target.

P010 Evaluation of antifungal efficacy of two novel cyclic lipopeptides of the class Bacillomycin from Bacillus subtilis RLID 12.1 in a murine model of invasive candidiasis

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PMObjectiveTo evaluate the in vivo efficacy of HPLC–purified antifungal lipopeptides (AF4 and AF5) in a murine model of disseminated candidiasis.Methods C. albicans AMR16294 isolate was used for all the in vivo experiments. A total of 6-week-old pathogen-free, female BALB/c mice, weighing 20-25 g were used for all animal experiments. For Kaplan-Mier analysis, mice were rendered neutropenic by a loading dose of 200 mg/kg cyclophosphamide three days prior (D-3) to infection and 150 mg/kg (D + 1) maintenance dose on day 1 post-infection (D + 1). A total of 60 mice were randomized into 8 different groups with 5 or 6 animals in each group. Animals were infected with 100μL of ∼ 1 × 10⁵ blastospores (corresponding to LD90) via the lateral tail vein. AF4 and AF5 were formulated in sterile PBS and administered intraperitoneally at doses of 5 mg/kg and 10 mg/kg body weight and compared with a clinically-relevant human equivalent dose of caspofungin. AF4, AF5, caspofungin, or vehicle were administered at 1 h and 24 h post-infection. The survival of the mice was monitored for 14 days post-infection. For organ fungal-burden assessment, mice from each group were euthanized by CO2 inhalation, and the organs were aseptically removed, homogenized, and cultured on SDA.ResultsBoth the doses of AF4 significantly reduced the mortality of mice compared to vehicle-treated mice. The survival over 2 weeks in 5 mg/kg, 10 mg/kg, and caspofungin arms were similar and no death was reported in the three groups (P <.01). In contrast, the mortality in-vehicle- administered group was 80% with a median survival of 8 days. A similar survival benefit was observed in AF5-treated mice. While the median survival in the vehicle-treated arm was 5 days, the 2-week survival in 5 mg/kg and 10 mg/kg arms was 80%-100%, comparable to that in the caspofungin arm (P <.01) (Fig. 1).The median CFU/g kidney tissue in 5 mg/kg arm of AF4 was 1.3 × 10⁴ equivalent to a 4-log reduction compared to the vehicle arm (3.8 × 10⁸ CFU/g kidney, P <.0001). The in vivo efficacy was higher at a higher dose with the kidney homogenates of 10 mg/kg arm yielding sterile cultures comparable to that of CAS arm (Fig. 2). Similar organ fungal-burden reduction was noted in heart and splenic tissues with a median cfu/g tissue of 1.3 × 10⁴ in 10 mg/kg, while CAS arms yielded sterile cultures.In AF5 treated groups, the median cfu/g kidney tissue in 5 mg/kg arm was 1.3 × 10⁴, however, the heart and splenic tissue homogenates yielded less fungal burden with median (q2) cfu/g as 0, while q3 of 6.7 × 10³and 1.3 × 10⁴, respectively (Fig. 2).ConclusionBoth the antifungal compounds demonstrated a remarkable in vivo efficacy against C. albicans with a significant improvement in survival and a reduction in the organ-fungal burden.

P032 Efficacy of novel azole compounds (ATTAF-1 and ATTAF-2) against Candida albicans in a murine model of invasive Candidiasis

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PMObjectives Candida albicans is the most common cause of nosocomial bloodstream infections and are associated with substantial morbidity and mortality in immunocompromised individuals. However, limited therapeutic approaches against invasive candidiasis are available. The rise in antifungal resistance highlights the urgent need to develop new therapeutic options and novel treatment strategies to combat later infections. A novel compound Aryl-1, 2, 4-triazol-3- ylthio, fluconazole alcohol-derived analogs (ATTAFs), has newly developed with potent in vitro activity against Candida species, including fluconazole-resistant isolates. The objective of this study was to further evaluate the in vivo effectiveness in a murine model of invasive candidiasis due to C. albicans.MethodsTreatment with ATTAF-1 and ATTAF-2 significantly increased the survival of infected mice compared to the control group (5% DMSO plus inoculum).ResultsThe antifungal action of ATTAF-1 and ATTAF-2 and their median survival time provided no evidence of a difference versus fluconazole. Although there was an obvious fungal load (mean log CFU/g of tissue) decrease by ATTAF-1 and ATTAF-2 in the kidney, spleen, and liver of the treated mice in comparison with the control group and not similar to each other in regard of the dose, fluconazole showed a significant decrease in the number of fungal loads, similar to the group treated with ATTAF-1 and ATTAF-2. Nevertheless, the results of this study indicate that the use of ATTAF-1 and ATTAF-2 as a therapeutic agent can exert significant in vitro and in vivo antifungal effects against C. albicans, increasing animal survival and significantly decreasing fungal loads.ConclusionAlthough we have identified two new compounds, ATTAF-1 and ATTAF-2, as novel promising Candidates for the treatment of Candida infection, more studies of ATTAF-1 and ATTAF-2 activity and their action mechanisms in animal models are warranted to enhance our understanding and establish their efficacy.

The prophylactic effects of monoclonal antibodies targeting the cell wall Pmt4 protein epitopes of Candida albicans in a murine model of invasive candidiasis.

Candida albicans (C. albicans) is the most prevalent opportunistic human pathogen, accounting for approximately half of all clinical cases of candidemia. Resistance to the existing antifungal drugs is a major challenge in clinical therapy, necessitating the development and identification of novel therapeutic agents and potential treatment strategies. Monoclonal antibody-based immunotherapy represents a promising therapeutic strategy against disseminated candidiasis. Protein mannosyltransferase (Pmt4) encodes mannosyltransferases initiating O-mannosylation of secretory proteins and is essential for cell wall composition and virulence of C. albicans. Therefore, the Pmt4 protein of C. albicans is an attractive target for the discovery of alternative antibody agents against invasive C. albicans infections. In the present study, we found that monoclonal antibodies (mAbs) C12 and C346 specifically targeted the recombinant protein mannosyltransferase 4 (rPmt4p) of C. albicans. These mAbs were produced and secreted by hybridoma cells isolated from the spleen of mice that were initially immunized with the purified rPmt4p to generate IgG antibodies. The mAbs C12 and C346 exhibited high affinity to C. albicans whole cells. Remarkably, these mAbs reduced the fungal burden, alleviated inflammation in the kidneys, and prolonged the survival rate significantly in the murine model of systemic candidiasis. Moreover, they could activate macrophage opsonophagocytic killing and neutrophil killing of C. albicans strain in vitro. These results suggested that anti-rPmt4p mAbs may provide immunotherapeutic interventions against disseminated candidiasis via opsonophagocytosis and opsonic killing activity. Our findings provide evidence for mAbs as a therapeutic option for the treatment of invasive candidiasis.

Guanylated Hyperbranched Polylysines with High In Vitro and In Vivo Antifungal Activity.

With the rapid growth of fungal infections and the emergence of multi-drug resistant (MDR) fungal strains, new antifungals with novel mechanisms are a pressing need to tackle this emerging health problem. Herein it is reported for the first time that hyperbranched polylysine (HPL) shows antifungal activities against Candida, especially for drug-sensitive and MDR C. albicans strains, and broad-spectrum antibacterial activities against both Gram-negative and Gram-positive bacteria. The high antimicrobial activities are ascribed to the high charge density and compact size of the globular structure of HPL. The in vitro antifungal activities of HPL3 are further enhanced by the modification of amine groups to form guanylated polylysines (HPL3-Gxs). Similar to antimicrobial peptides (AMPs), HPLs and HPL3-Gxs interact with and lyse the membranes of microbes, which mitigates the emergence of drug resistance. HPLs and HPL3-Gxs demonstrate excellent in vivo antimicrobial efficacies against both lethal C. albicans challenge in the invasive candidiasis model and lethal Methicillin resistant Staphylococcus aureus challenge in the peritonitis model, and have potentials as broad-spectrum antimicrobials.

Commentary: Experimental Mouse Models of Invasive Candidiasis Caused by Candida auris and Other Medically Important Candida Species.

The study ““Experimental Mouse Models of Disseminated Candida auris Infection” provides the first insight into the critical role of C5 in the host antimicrobial defense to disseminated candidiasis caused by C. auris. This study also establishes an inbred A/J mouse model of systemic C. auris infection without drug-induced immunosuppression. C. auris has become the first fungal pathogen causing global public health threat due to its multidrug resistance (MDR) and persistence in hospital and nursing home settings. Currently, as compared to C. albicans, very limited animal models are available to study the progression of non-albicans Candida (NAC) species including C. auris. We have successfully established immunosuppressed C57BL/6, BALB/c and A/J murine models of disseminated candidiasis caused by five clinically significant Candida species: C. albicans, C. glabrata, C. tropicalis, C. parapsilosis and C. auris. Here we also report updated progress of some important mouse models for C. auris infection in the field. These valuable mouse models can be used for the assessment of antifungal drugs, evaluation of potential vaccines and monoclonal antibodies (mAbs) to protect before and after candidiasis, and comparison of pathogenicity of different Candida species.

Induction and analysis of systemic C. albicans infections in mice.

The human fungal pathogen Candida albicans (C. albicans) causes invasive candidiasis, characterized by fatal organ failure due to disseminated fungal growth and inflammatory damage. To better understand fungal pathogenicity mechanisms and host protective responses, a murine model of invasive candidiasis has been developed in which C. albicans is administered systemically via intravenous injection. In this infection model, all major tissues are seeded within 0-4h. Of all the peripheral organs, the kidneys provide the most favorable niches for fungal proliferation and the morphogenetic switch to a hyphal state. As a consequence, the kidneys are a focal point for analyzing many of the genetic and immunological factors that underlie disease progression. Herein, we describe a number of well-established techniques that allow investigation into specific mechanisms that impact host-pathogen interactions.

DC-SIGN targets amphotericin B-loaded liposomes to diverse pathogenic fungi

BackgroundLife-threatening invasive fungal infections are treated with antifungal drugs such as Amphotericin B (AmB) loaded liposomes. Our goal herein was to show that targeting liposomal AmB to fungal cells with the C-type lectin pathogen recognition receptor DC-SIGN improves antifungal activity. DC-SIGN binds variously crosslinked mannose-rich and fucosylated glycans and lipomannans that are expressed by helminth, protist, fungal, bacterial and viral pathogens including three of the most life-threatening fungi, Aspergillus fumigatus, Candida albicans and Cryptococcus neoformans. Ligand recognition by human DC-SIGN is provided by a carbohydrate recognition domain (CRD) linked to the membrane transit and signaling sequences. Different combinations of the eight neck repeats (NR1 to NR8) expressed in different protein isoforms may alter the orientation of the CRD to enhance its binding to different glycans.ResultsWe prepared two recombinant isoforms combining the CRD with NR1 and NR2 in isoform DCS12 and with NR7 and NR8 in isoform DCS78 and coupled them to a lipid carrier. These constructs were inserted into the membrane of pegylated AmB loaded liposomes AmB-LLs to produce DCS12-AmB-LLs and DCS78-AmB-LLs. Relative to AmB-LLs and Bovine Serum Albumin coated BSA-AmB-LLs, DCS12-AmB-LLs and DCS78-AmB-LLs bound more efficiently to the exopolysaccharide matrices produced by A. fumigatus, C. albicans and C. neoformans in vitro, with DCS12-AmB-LLs performing better than DCS78-AmB-LLs. DCS12-AmB-LLs inhibited and/or killed all three species in vitro significantly better than AmB-LLs or BSA-AmB-LLs. In mouse models of invasive candidiasis and pulmonary aspergillosis, one low dose of DCS12-AmB-LLs significantly reduced the fungal burden in the kidneys and lungs, respectively, several-fold relative to AmB-LLs.ConclusionsDC-SIGN’s CRD specifically targeted antifungal liposomes to three highly evolutionarily diverse pathogenic fungi and enhanced the antifungal efficacy of liposomal AmB both in vitro and in vivo. Targeting significantly reduced the effective dose of antifungal drug, which may reduce drug toxicity, be effective in overcoming dose dependent drug resistance, and more effectively kill persister cells. In addition to fungi, DC-SIGN targeting of liposomal packaged anti-infectives have the potential to alter treatment paradigms for a wide variety of pathogens from different kingdoms including protozoans, helminths, bacteria, and viruses which express its cognate ligands.

Candida auris Cell Wall Mannosylation Contributes to Neutrophil Evasion through Pathways Divergent from Candida albicans and Candida glabrata.

ABSTRACTCandida auris, a recently emergent fungal pathogen, has caused invasive infections in health care settings worldwide. Mortality rates approach 60% and hospital spread poses a public health threat. Compared to other Candida spp., C. auris avoids triggering the antifungal activity of neutrophils, innate immune cells that are critical for responding to many invasive fungal infections, including candidiasis. However, the mechanism underpinning this immune evasion has been largely unknown. Here, we show that C. auris cell wall mannosylation contributes to the evasion of neutrophils ex vivo and in a zebrafish infection model. Genetic disruption of mannosylation pathways (PMR1 and VAN1) diminishes the outer cell wall mannan, unmasks immunostimulatory components, and promotes neutrophil engagement, phagocytosis, and killing. Upon examination of these pathways in other Candida spp. (Candida albicans and Candida glabrata), we did not find an impact on neutrophil interactions. These studies show how C. auris mannosylation contributes to neutrophil evasion though pathways distinct from other common Candida spp. The findings shed light on innate immune evasion for this emerging pathogen.IMPORTANCE The emerging fungal pathogen Candida auris presents a global public health threat. Therapeutic options are often limited for this frequently drug-resistant pathogen, and mortality rates for invasive disease are high. Previous study has demonstrated that neutrophils, leukocytes critical for the antifungal host defense, do not efficiently recognize and kill C. auris. Here, we show how the outer cell wall of C. auris promotes immune evasion. Disruption of this mannan polysaccharide layer renders C. auris susceptible to neutrophil killing ex vivo and in a zebrafish model of invasive candidiasis. The role of these mannosylation pathways for neutrophil evasion appears divergent from other common Candida species.

Review of T-2307, an Investigational Agent That Causes Collapse of Fungal Mitochondrial Membrane Potential.

Invasive infections caused by Candida that are resistant to clinically available antifungals are of increasing concern. Increasing rates of fluconazole resistance in non-albicans Candida species have been documented in multiple countries on several continents. This situation has been further exacerbated over the last several years by Candida auris, as isolates of this emerging pathogen that are often resistant to multiple antifungals. T-2307 is an aromatic diamidine currently in development for the treatment of invasive fungal infections. This agent has been shown to selectively cause the collapse of the mitochondrial membrane potential in yeasts when compared to mammalian cells. In vitro activity has been demonstrated against Candida species, including C. albicans, C. glabrata, and C. auris strains, which are resistant to azole and echinocandin antifungals. Activity has also been reported against Cryptococcus species, and this has translated into in vivo efficacy in experimental models of invasive candidiasis and cryptococcosis. However, little is known regarding the clinical efficacy and safety of this agent, as published data from studies involving humans are not currently available.

The Role of New Posaconazole Formulations in the Treatment of Candida albicans Infections: Data from an In Vitro Pharmacokinetic-Pharmacodynamic Model.

Posaconazole is more active than fluconazole against Candida albicansin vitro and is approved for the treatment of oropharyngeal candidiasis but not for that of invasive candidiasis (IC). Here, we explored the efficacy of posaconazole against C. albicans in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model of IC and determined the probability of pharmacodynamic target attainment for the oral solution and intravenous (i.v.)/tablet formulations. Three clinical C. albicans isolates (posaconazole MICs, 0.008 to 0.25 mg/liter) were studied in the in vitro PK/PD dilution model simulating steady-state posaconazole PK. The in vitro exposure-effect relationship, area under the 24-h free drug concentration curve (fAUC0-24)/MIC, was described and compared with in vivo outcome in animals with IC. PK/PD susceptibility breakpoints and trough levels required for optimal treatment were determined for EUCAST and CLSI 24-h/48-h (CLSI24h/CLSI48h) methods using the fAUC0-24/MIC associated with half-maximal activity (EI50) and Monte Carlo simulation analysis for oral solution (400 mg every 12 hours [q12h]) and i.v./tablet formulations (300 mg q24h). The in vitro mean (95% confidence interval [CI]) EI50 was 330 (183 to 597) fAUC0-24/MIC for CLSI24h and 169 (92 to 310) for EUCAST/CLSI48h methods, which are close to the near-stasis in vivo effect. The probability of target attainment for EI50 was estimated; for the wild-type isolates (MIC ≤ 0.06 mg/liter), it was low for the oral solution and higher than 95% for the i.v./tablet formulations for the EUCAST/CLSI48h methods but not for the CLSI 24-h method. Non-wild-type isolates with EUCAST/CLSI48h MICs of 0.125 and 0.25 mg/liter would require trough levels of >1.2 and >2.4 mg/liter, respectively. Posaconazole i.v./tablet formulations may have a role in the therapy of invasive infections by wild-type C. albicans isolates, provided that a steady state is reached quickly. A PK/PD susceptibility breakpoint at the epidemiological cutoff (ECV/ECOFF) of 0.06 mg/liter was determined.

ERG3-Encoding Sterol C5,6-DESATURASE in Candida albicans Is Required for Virulence in an Enterically Infected Invasive Candidiasis Mouse Model.

Gastrointestinal colonization by Candida species is considered the main source of candidemia. The ERG3 gene in Candida albicans encodes a sterol C5,6-desaturase, which is essential for ergosterol biosynthesis. Although ERG3 inactivation shows reduced virulence in mouse models of disseminated candidiasis, the role of ERG3 in intestinal infections is unknown. Here, we infected mice with the C. albicans strains CAE3DU3 and CAF2-1, containing mutant and wild-type ERG3, respectively, and studied gut infection and colonization by these strains. We found that the CAE3DU3 strain showed reduced colonization, pathogenesis, damage to gut mucosa, and chemokine production in the mouse model of invasive candidiasis. Additionally, mice inoculated with CAE3DU3 showed lower mortality than mice inoculated with CAF2-1 (p < 0.0001). Chemokines were less induced in the gut inoculated with CAE3DU3 than in the gut inoculated with CAF2-1. Histopathologically, although the wild-type gene was associated with a higher pathogenicity and invasion of the gut mucosa and liver tissues causing remarkable tissue necrosis, the erg3/erg3 mutant was associated with a higher accumulation of cells and lower damage to surrounding tissues than wild-type ERG3. These results establish that the ergosterol biosynthetic pathway may be associated with C. albicans gut colonization and subsequent dissemination.

Pharmacokinetic and pharmacodynamic profiling of generic amphotericin B colloidal dispersion in a rat model of invasive candidiasis

ObjectivesWe reported the pharmacokinetic/pharmacodynamic (PK/PD) targets of a biosimilar generic product of amphotericin B colloidal dispersion (G-ABCD) againstCandida albicans (MIC 1–2 μg/mL) in a rat model of invasive candidiasis (IC) to facilitate its precision administration. MethodsSingle-dose plasma PKs of G-ABCD was studied in a rat IC model following intravenous administration at doses of 0.0625–10 mg/kg. Amphotericin B concentrations were determined and PK parameters were calculated based on the concentrations in plasma. The efficacy of G-ABCD was evaluated after single administration by the log reduction of CFU counts in kidney, liver, spleen and lung. The relationship between G-ABCD PK/PD index and log CFU reduction in kidney was calculated. ResultsFollowing intravenous administration of G-ABCD at doses of 0.0625–10 mg/kg to rats, the maximum plasma concentration (Cmax) was 0.05–0.82 mg/L and the area under the concentration–time curve from 0 to 24 h (AUC0–24) was 0.50–5.29 mg h/L. G-ABCD showed potent antifungal activity against C. albicans C-13 with a maximum log CFU reduction of 2.1 in kidney. The mean AUC0–24/MIC target of G-ABCD against C. albicans was 0.97 for stasis, 1.40 for 1-log kill and 3.34 for 2-log kill, and the mean Cmax/MIC target was 0.063 for stasis, 0.097 for 1-log kill and 0.348 for 2-log kill. ConclusionsThe antifungal effect of G-ABCD was potent and correlated with AUC0–24/MIC and Cmax/MIC in this rat model of IC. The results of this study provide data for optimising G-ABCD dosing regimens and breakpoints for antifungals.

Targeting fungal virulence factor by small molecules: Structure-based discovery of novel secreted aspartic protease 2 (SAP2) inhibitors

Secreted aspartic protease 2 (SAP2), a kind of virulence factor, is an emerging new antifungal target. Using docking-based virtual screening and structure-based inhibitor design, a series of novel SAP2 inhibitors were successfully identified. Among them, indolone derivative 24a showed potent SAP2 inhibitory activity (IC50 = 0.92 μM). It blocked fungi biofilm and hypha formation by down-regulating the expression of genes SAP2, ECE1, ALS3 and EFG1. As a virulence factor inhibitor, compound 24a was inactive in vitro and showed potent in vivo efficacy in a murine model of invasive candidiasis. It represents a promising lead compound for the discovery of novel antifungal agents.

From bench to bedside: Perspectives on the utility of pharmacokinetics/pharmacodynamics in predicting the efficacy of antifungals in invasive candidiasis.

The aim of this perspective is to give an overlook on the utility of pharmacokinetics/pharmacodynamics (PK/PD) in predicting the efficacy of antifungals in invasive candidiasis. Overall, from the available literature it appears that bridging data of PK/PD of antifungals from the laboratory to the clinic for the treatment of invasive candidiasis are feasible only partially. Fluconazole is the only antifungal agent having the pharmacodynamic threshold of efficacy identified in experimental animal models convincingly validated in the clinical setting of invasive candidiasis as well. Conversely, for voriconazole and posaconazole data on this topic are very limited. For the echinocandins, robust PK/PD identified in the laboratory represented the rationale for defining differential clinical breakpoints of echinocandins against different species of Candida by the regulatory agencies. However, translation of the findings in the clinical setting provided conflicting results. Data on PK/PD of amphotericin B and flucytosine in models of invasive candidiasis are quite limited, and clinical studies assessing the role of drug exposure on efficacy are currently lacking. The expectation is that prospective studies could test more and more frequently the validity of experimental PK/PD data of antifungals in the clinical setting of invasive candidiasis. The findings could represent a step forward in addressing adequate antifungal stewardship programmes.

Implications of Evolving and Emerging Pharmacokinetic-Pharmacodynamic Research for Triazoles and Echinocandins

Clinicians should be encouraged to use pharmacokinetic-pharmacodynamic (PK-PD) studies to optimize antifungal drug dosing in the absence of robust comparative effectiveness data or in cases where evidence of causality has not yet been firmly established. The purpose of this article is to review how new triazole and echinocandin PK-PD studies have contributed to our current understanding of antifungal selection and dose optimization against invasive fungal infections. Emerging infections such as C. auris and novel antifungal drugs such as rezafungin will also be highlighted. Future research endeavors are suggested where currently robust clinical outcomes data associated with PK-PD target attainment are lacking. Recent results from clinical fluconazole PK-PD studies may indicate that unique AUC24/MIC thresholds exist for specific Candida species. The inability of recent studies to confirm previous fluconazole AUC24/MIC clinical PK-PD targets of 11 to 400 may also be due to previously unrecognized PK variability in special patient populations such as those with augmented renal clearance. A free AUC24/MIC threshold of 25 appears to be conserved across the azole antifungal class in animal models of invasive candidiasis. Current therapeutic drug monitoring guidance with voriconazole, posaconazole, and itraconazole has been used to indirectly confirm pre-clinical AUC24/MIC PK-PD targets in invasive candidiasis and aspergillosis. Elucidation of the PK-PD targets in pre-clinical models has led to successful isavuconazole dose optimization in human studies and has contributed to dosing recommendations for the novel echinocandin rezafungin. PK-PD research will also be important in guiding antifungal selection against infections caused by emerging pathogens, such as Candida auris, and those caused by fungi for which reduced susceptibility is a growing concern, including Coccidioides species and azole-resistant Aspergillus fumigatus. PK-PD research may be used to inform treatment decisions for rare fungal infections, infections with rapidly changing epidemiology, in patient populations expected to have altered pharmacokinetics, for novel antifungal drugs or those with new formulations, and in cases where evidence of causality cannot be established from large randomized comparative studies. A number of animal models have been developed and more clinical PK-PD studies are being conducted. In the absence of clinical PK-PD outcome data in human studies, researchers have expanded the use of currently available therapeutic drug monitoring to gain insight into possible PK-PD targets.