In vitro susceptibilities of zygomycetes to combinations of antimicrobial agents

Auranofin is active against Histoplasma capsulatum and reduces the expression of virulence-related genes

BACKGROUND

Auranofin is an approved anti-rheumatic drug that has a broad-range inhibitory action against several microorganisms, including human pathogenic fungi. The auranofin activity against Histoplasma capsulatum, the dimorphic fungus that causes histoplasmosis, has not been properly addressed. Since there are few therapeutic options for this life-threatening systemic mycosis, this study evaluated the effects of auranofin on H. capsulatum growth and expression of virulence factors.

METHODOLOGY/PRINCIPAL FINDINGS

Minimal inhibitory and fungicidal concentrations (MIC and MFC, respectively) of auranofin against 15 H. capsulatum strains with distinct genetic backgrounds were determined using the yeast form of the fungus and a microdilution protocol. Auranofin activity was also assessed on a macrophage model of infection and on a Tenebrio molitor invertebrate animal model. Expression of virulence-related genes was compared between auranofin treated and untreated H. capsulatum yeast cells using a quantitative PCR assay. Auranofin affected the growth of different strains of H. capsulatum, with MIC and MFC values ranging from 1.25 to 5.0 μM and from 2.5 to >10 μM, respectively. Auranofin was able to kill intracellular H. capsulatum yeast cells and conferred protection against the fungus in the experimental animal model of infection. Moreover, the expression of catalase A, HSP70, superoxide dismutase, thioredoxin reductase, serine proteinase, cytochrome C peroxidase, histone 2B, formamidase, metallopeptidase, Y20 and YPS3 proteins were reduced after six hours of auranofin treatment. CONCLUSIONS/SIGNIFICANCE: Auranofin is fungicidal against H. capsulatum and reduces the expression of several virulence-related genes, which makes this anti-rheumatic drug a good candidate for new medicines against histoplasmosis.

Comparison of the antifungal activity of the pyrimidine analogs flucytosine and carmofur against human-pathogenic dematiaceous fungi

Chromoblastomycosis (CBM) and pheohyphomycosis (PHM) are the most common implantation mycoses caused by dematiaceous fungi. In the past, flucytosine (5-FC) has been used to treat CBM, but development of resistance is common. Carmofur belongs to the same class as 5-FC and has in vitro inhibitory activity against the main agents of CBM and PHM. The aim of this study was to compare the action of these two pyrimidine analog drugs against CBM and PHM agents. The minimum inhibitory concentration (MIC) and the selectivity index based on cytotoxicity tests of these two drugs against some agents of these mycoses were determined, with carmofur presenting a higher selectivity index than 5-FC. Carmofur demonstrated here synergistic interactions with itraconazole and amphotericin B against Exophiala heteromorpha, Fonsecaea pedrosoi, Fonsecaea monophora, and Fonsecaea nubica strains. Additionally, carmofur plus itraconazole demonstrated here synergism against a Phialophora verrucosa strain. To evaluate the development of carmofur resistance, passages in culture medium containing subinhibitory concentrations of this pyrimidine analog were carried out, followed by in vitro susceptibility tests. Exophiala dermatitidis quickly developed resistance, whereas F. pedrosoi took seven passages in carmofur-supplemented medium to develop resistance. Moreover, resistance was permanent in E. dermatitidis but transient in F. pedrosoi. Hence, carmofur has exhibited certain advantages, albeit accompanied by limitations such as the development of resistance, which was expected as with 5-FC. This underscores its therapeutic potential in combination with other drugs, emphasizing the need for a meticulous evaluation of its application in the fight against dematiaceous fungi.

Repurposing Benzimidazoles against Causative Agents of Chromoblastomycosis: Albendazole Has Superior In Vitro Activity Than Mebendazole and Thiabendazole

Chromoblastomycosis (CBM) is a neglected human implantation mycosis caused by several dematiaceous fungal species. Currently available therapy is usually associated with physical methods, especially surgery, and with high refractoriness. Therefore, drug discovery for CBM is essential. Drug repositioning is a strategy used to facilitate the discovery of new treatments for several diseases. The aim of this study was to discover substances with antifungal activity against CBM agents from a collection of drugs previously approved for use in human diseases. A screening was performed with the NIH Clinical Collection against Fonsecaea pedrosoi. Ten substances, with clinical applicability in CBM, inhibited fungal growth by at least 60%. The minimum inhibitory concentration (MIC) of these substances was determined against other CBM agents, and the benzimidazoles albendazole, mebendazole and thiabendazole presented the lowest MIC values. The selectivity index, based on MIC and cytotoxicity of these substances, revealed albendazole to be more selective. To investigate a possible synergism of this benzimidazole with itraconazole and terbinafine, the chequerboard method was used. All interactions were classified as indifferent. Our current results suggest that benzimidazoles have repositioning potential against CBM agents. Albendazole seems to be the most promising, since it presented the highest selectivity against all dematiaceous fungi tested.

Epidemiology, Modern Diagnostics, and the Management of Mucorales Infections

Mucormycosis is an uncommon, yet deadly invasive fungal infection caused by the Mucorales moulds. These pathogens are a WHO-assigned high-priority pathogen group, as mucormycosis incidence is increasing, and there is unacceptably high mortality with current antifungal therapies. Current diagnostic methods have inadequate sensitivity and specificity and may have issues with accessibility or turnaround time. Patients with diabetes mellitus and immune compromise are predisposed to infection with these environmental fungi, but COVID-19 has established itself as a new risk factor. Mucorales also cause healthcare-associated outbreaks, and clusters associated with natural disasters have also been identified. Robust epidemiological surveillance into burden of disease, at-risk populations, and emerging pathogens is required. Emerging serological and molecular techniques may offer a faster route to diagnosis, while newly developed antifungal agents show promise in preliminary studies. Equitable access to these emerging diagnostic techniques and antifungal therapies will be key in identifying and treating mucormycosis, as delayed initiation of therapy is associated with higher mortality.

New possibilities for chromoblastomycosis and phaeohyphomycosis treatment: identification of two compounds from the MMV Pathogen Box® that present synergism with itraconazole

BACKGROUND

Black fungi of the Herpotrichiellaceae family are agents of chromoblastomycosis and phaeohyphomycosis. There are few therapeutic options for these infections and it is common to associate antifungal drugs in their treatment.

OBJECTIVES

To investigate the Medicines for Malaria Venture (MMV) Pathogen Box^® for possible compounds presenting synergism with antifungal drugs used to treat black fungal infections.

METHODS

An initial screening of the Pathogen Box^® compounds was performed in combination with itraconazole or terbinafine at sub-inhibitory concentrations against Fonsecaea pedrosoi. Hits were further tested against eight Herpotrichiellaceae using the checkerboard method.

FINDINGS

No synergism was observed with terbinafine. MMV687273 (SQ109) and MMV688415 showed synergism with itraconazole against F. pedrosoi. Synergism of these compounds was confirmed with some black fungi by the checkerboard method. SQ109 and itraconazole presented synergism for Exophiala dermatitidis, F. pedrosoi, F. monophora and F. nubica, with fungicidal activity for F. pedrosoi and F. monophora. MMV688415 presented synergism with itraconazole only for F. pedrosoi, with fungicidal activity. The synergic compounds had high selectivity index values when combined with itraconazole.

MAIN CONCLUSIONS

These compounds in combination, particularly SQ109, are promising candidates to treat Fonsecaea spp. and E. dermatitidis infections, which account for most cases of chromoblastomycosis and phaeohyphomycosis.

Current Treatment Options for COVID-19 Associated Mucormycosis: Present Status and Future Perspectives

Mucormycosis has become increasingly associated with COVID-19, leading to the use of the term “COVID-19 associated mucormycosis (CAM)”. Treatment of CAM is challenging due to factors such as resistance to many antifungals and underlying co-morbidities. India is particularly at risk for this disease due to the large number of patients with COVID-19 carrying comorbidities that predispose them to the development of mucormycosis. Additionally, mucormycosis treatment is complicated due to the atypical symptoms and delayed presentation after the resolution of COVID-19. Since this disease is associated with increased morbidity and mortality, early identification and diagnosis are desirable to initiate a suitable combination of therapies and control the disease. At present, the first-line treatment involves Amphotericin B and surgical debridement. To overcome limitations associated with surgery (invasive, multiple procedures required) and amphotericin B (toxicity, extended duration and limited clinical success), additional therapies can be utilized as adjuncts or alternatives to reduce treatment duration and improve prognosis. This review discusses the challenges associated with treating CAM and the critical aspects for controlling this invasive fungal infection—early diagnosis and initiation of therapy, reversal of risk factors, and adoption of a multipronged treatment strategy. It also details the various therapeutic options (in vitro, in vivo and human case reports) that have been used for the treatment of CAM.

Improved In Vitro Anti-Mucorales Activity and Cytotoxicity of Amphotericin B with a Pegylated Surfactant

The aim of this study was to evaluate the effect of the combination of amphotericin B (AmB) and various non-ionic surfactants on the anti-Mucorales activity of AmB, the toxicity of the combination on eukaryotic cells and the modification of AmB aggregation states. Checkerboards were performed on five genera of Mucorales (12 strains) using several combinations of different surfactants and AmB. These data were analyzed by an E_max model. The effect of surfactants on the cytotoxic activity of AmB was then evaluated for red blood cells and two eukaryotic cell lines by absorbance and propidium iodide internalization. Finally, the effect of polyethylene glycol (15)-hydroxystearate (PEG15HS) on the aggregation states of AmB was evaluated by UV-visible spectrometry. PEG15HS increased the efficacy of AmB on four of the five Mucorales genera, and MICs of AmB were decreased up to 68-fold for L. ramosa. PEG15HS was the only surfactant to not increase the cytotoxic activity of AmB. Finally, the analysis of AmB aggregation states showed that the increased efficacy of AmB and the absence of toxicity are related to an increase in monomeric and polyaggregated forms of AmB at the detriment of the dimeric form. In conclusion, PEG15HS increases the in vitro efficacy of AmB against Mucorales at low concentration, without increasing its toxicity; this combination could therefore be evaluated in the treatment of mucormycosis.

Alternative treatment of fungal infections: Synergy with non-antifungal agents

Fungal infections are responsible for high mortality rates in immunocompromised and high-risk surgical patients. Therapy failures during the last decades due to increasing multidrug resistance demand innovative strategies for novel and effective antifungal drugs. Synergistic combinations of antifungals with non-antifungal agents highlight a pragmatic strategy to reduce the development of drug resistance and potentially repurpose known compounds with other functions to bypass costly and time-consuming novel drug development.

Mucormycosis treatment: Recommendations, latest advances, and perspectives

Mucormycosis are life-threatening fungal infections especially affecting immunocompromised or diabetic patients. Despite treatment, mortality remains high (from 32 to 70% according to organ involvement). This review provides an update on mucormycosis management. The latest recommendations strongly recommend as first-line therapy the use of liposomal amphotericin B (≥5mg/kg) combined with surgery whenever possible. Isavuconazole and intravenous or delayed-release tablet forms of posaconazole have remained second-line. Many molecules are currently in development to fight against invasive fungal diseases but few have demonstrated efficacy against Mucorales. Despite in vitro efficacy, combinations of treatment have failed to demonstrate superiority versus monotherapy. Adjuvant therapies are particularly complex to evaluate without prospective randomized controlled studies, which are complex to perform due to low incidence rate and high mortality of mucormycosis. Perspectives are nonetheless encouraging. New approaches assessing relationships between host, fungi, and antifungal drugs, and new routes of administration such as aerosols could improve mucormycosis treatment.

A screening of the MMV Pathogen Box® reveals new potential antifungal drugs against the etiologic agents of chromoblastomycosis

Chromoblastomycosis (CBM) is a chronic subcutaneous mycosis caused by traumatic implantation of many species of black fungi. Due to the refractoriness of some cases and common recurrence of CBM, a more effective and less time-consuming treatment is mandatory. The aim of this study was to identify compounds with in vitro antifungal activity in the Pathogen Box® compound collection against different CBM agents. Synergism of these compounds with drugs currently used to treat CBM was also assessed. An initial screening of the drugs present in this collection at 1 μM was performed with a Fonsecaea pedrosoi clinical strain according to the EUCAST protocol. The compounds with activity against this fungus were also tested against other seven etiologic agents of CBM (Cladophialophora carrionii, Phialophora verrucosa, Exophiala jeanselmei, Exophiala dermatitidis, Fonsecaea monophora, Fonsecaea nubica, and Rhinocladiella similis) at concentrations ranging from 0.039 to 10 μM. The analysis of potential synergism of these compounds with itraconazole and terbinafine was performed by the checkerboard method. Eight compounds inhibited more than 60% of the F. pedrosoi growth: difenoconazole, bitertanol, iodoquinol, azoxystrobin, MMV688179, MMV021013, trifloxystrobin, and auranofin. Iodoquinol produced the lowest MIC values (1.25-2.5 μM) and MMV688179 showed MICs that were higher than all compounds tested (5 - >10 μM). When auranofin and itraconazole were tested in combination, a synergistic interaction (FICI = 0.37) was observed against the C. carrionii isolate. Toxicity analysis revealed that MMV021013 showed high selectivity indices (SI ≥ 10) against the fungi tested. In summary, auranofin, iodoquinol, and MMV021013 were identified as promising compounds to be tested in CBM models of infection.

Antifungal combinations in Mucorales: A microbiological perspective

Mucormycosis mostly affects immunocompromised patients and is associated with a high morbidity and mortality despite currently available treatments. In that context, combination therapy might be the key to a better outcome for these patients. Purpose of this review is to summarise and to discuss the current combination data obtained in vitro, in vivo in animal models of mucormycosis, and in patients. In vitro combination studies showed that most of the interactions between antifungal drugs were indifferent, even though that some synergistic interactions were achieved for the combination of echinocandins with either azoles or amphotericin B. Importantly, antagonism was never observed. Animal models of mucormycosis focused on infections caused by Rhizopus arrhizus, neglecting most other species responsible for human disease. In these experimental animal models, no strong interactions have been demonstrated, although a certain degree of synergism has been reported in some instances. Combinations of antifungals with non-antifungal drugs have also been largely explored in vitro and in animal models and yielded interesting results. In patients with ketoacidosis and rhino-orbito-cerebral infection, combination of polyene with caspofungin was effective. In contrast, despite promising experimental data, adjunctive therapy with the iron chelator deferasirox was unfavourable and was associated with a higher mortality than monotherapy with liposomal amphotericin B. More combinations have to be tested in vitro and a much larger panel of Mucorales species has to be tested in vivo to give a valuable statement if antifungal combination therapy could be an effective treatment strategy in patients with mucormycosis.

In Vitro and In Vivo Evaluation of Voriconazole-Containing Antifungal Combinations against Mucorales Using a Galleria mellonella Model of Mucormycosis

Mucorales are resistant to most antifungals. Mucormycosis associated mortality is unacceptable and new treatment approaches are needed. The objectives of this work were (i) to evaluate the nature and intensity of the in vitro effect of three drugs combinations which included voriconazole (plus amphotericin B, posaconazole and caspofungin) against 25 strains of six different Mucorales species; (ii) to evaluate a Galleria mellonella mucormycosis model; and (iii) to establish if any in vitro⁻in vivo correlation exists. As expected, amphotericin B and posaconazole were the most active drugs when tested alone. However, species-specific differences were found. The ΣFICs varied according to the used combination. Only five strains showed synergism when voriconazole was combined with posaconazole and three strains when combined with amphotericin B. Microscopic hyphae alteration were observed for some isolates when confronted against drugs combinations. Using a Galleria mellonella mucormycosis model, better survival was seen in voriconazole plus amphotericin B and plus caspofungin combined treatments when compared with AMB alone for R. microsporus. These survival improvements were obtained using a 32-fold lower amphotericin B doses when combined with VRC than when treated with the polyene alone. These lower antifungal doses emulate the antifungal concentrations where the microscopic hyphae alterations were seen.

Molecular identification and antifungal susceptibility profiles of clinical strains of Fonsecaea spp. isolated from patients with chromoblastomycosis in Rio de Janeiro, Brazil

BACKGROUND

Chromoblastomycosis (CBM) is a difficult-to-treat chronic subcutaneous mycosis. In Brazil, the main agent of this disease is Fonsecaea pedrosoi, which is phenotypically very similar to other Fonsecaea species, differing only genetically. The correct species identification is relevant since different species may differ in their epidemiologic aspects, clinical presentation, and treatment response.

METHODOLOGY/PRINCIPAL FINDINGS

Partial sequencing of the internal transcribed spacer (ITS) was used to identify twenty clinical isolates of Fonsecaea spp. Their in vitro antifungal susceptibility was determined using the broth microdilution method, according to the M38-A2 protocol. Amphotericin B (AMB), flucytosine (5FC), terbinafine (TRB), fluconazole (FLC), itraconazole (ITC), ketoconazole (KTC), posaconazole (POS), voriconazole (VRC), ravuconazole (RVC), caspofungin (CAS), and micafungin (MFG) were tested. The association between ITC/TRB, AMB/5FC, and ITC/CAS was studied by the checkerboard method to check synergism. The available patients' data were correlated with the obtained laboratory results. Fonsecaea monophora (n = 10), F. pedrosoi (n = 5), and F. nubica (n = 5) were identified as CBM' agents in the study. TRB and VRC were the drugs with the best in vitro activity with minimal inhibitory concentrations (MIC) lower than 0.25 mg/L. On the other hand, FLC, 5FC, AMB, and MFG showed high MICs. The AMB/5FC combination was synergistic for three F. monophora strains while the others were indifferent. Patients had moderate or severe CBM, and ITC therapy was not sufficient for complete cure in most of the cases, requiring adjuvant surgical approaches.

CONCLUSIONS/SIGNIFICANCE

F. monophora, the second most frequent Fonsecaea species in South America, predominated in patients raised and born in Rio de Janeiro, Brazil, without cerebral involvement in these cases. TRB, VRC, and the AMB/5FC combination should be further investigated as a treatment option for CBM.

Invasive Fungal Infections in the Critically Ill Patient

Invasive fungal infections have become an increasingly prevalent and disturbing problem in critically ill patients. The advent of broad-spectrum antibacterial therapy and immunosuppressant therapy, among other factors such as mechanical ventilation, places the intensive care patient at significant risk for infection with pathogenic fungi. Most patients who become infected with invasive fungi, especially Candida species, have been previously colonized with the offending organism, lending to the notion that colonization precedes infection inmany cases. Despite an ever-increasing array of antifungal therapy for these infections, mortality rates remain extremely high, especially when the bloodstream is the primary site of infection. In addition, a shift toward more resistant pathogens such asCandida glabrata, Candida krusei, and moldswill provide clinicianswith therapeutic challenges for many years. The wide variation in acquisition cost across antifungal agents adds an additional layer of complexity to clinical decision making. Newer antifungal agents, each with its own advantages and disadvantages, have become available in recent years. Placing each agent in its appropriate niche is a dilemma that has yet to be solved.

Mucormycosis Rhinosinusitis at Diagnosis of Acute Lymphoblastic Leukemia: Diagnostics and Management Challenges in a Low-Middle-income Country

We present the case of an adolescent with mucor rhinosinusitis diagnosed concomitantly with acute lymphoblastic leukemia at a hospital in Tegucigalpa, Honduras. We also discuss the challenges faced in the dual management of hematologic malignancies and invasive fungal disease in a low-middle-income country, such as access to diagnostics, immunosuppressants, imaging, and antifungals. Despite these shortcomings, the patient was successfully treated for both the diseases. Low-middle-income country hospitals can effectively treat invasive fungal diseases by providing adequate diagnostic and support services, which can improve the outcomes of pediatric cancer patients.

Pathogenesis and host defence against Mucorales: the role of cytokines and interaction with antifungal drugs

Innate immune response, including macrophages, neutrophils and dendritic cells and their respective receptors, plays an important role in host defences against Mucorales with differential activity against specific fungal species, while adaptive immunity is not the first line of defence. A number of endogenous and exogenous factors, such as cytokines and growth factors as well as certain antifungal agents have been found that they influence innate immune response to these organisms. Used alone or especially in combination have been shown to exert antifungal effects against Mucorales species. These findings suggest novel ways of adjunctive therapy for patients with invasive mucormycosis.

Heat shock protein 90 and calcineurin pathway inhibitors enhance the efficacy of triazoles against Scedosporium prolificans via induction of apoptosis

Scedosporium prolificans is a pathogenic mold resistant to current antifungals, and infection results in high mortality. Simultaneous targeting of both ergosterol biosynthesis and heat shock protein 90 (Hsp90) or the calcineurin pathway in S. prolificans may be an important strategy for enhancing the potency of antifungal agents. We hypothesized that the inactive triazoles posaconazole (PCZ) and itraconazole (ICZ) acquire fungicidal activity when combined with the calcineurin inhibitor tacrolimus (TCR) or Hsp90 inhibitor 17-demethoxy-17-(2-propenylamino) geldanamycin (17AAG). PCZ, ICZ, TCR and 17AAG alone were inactive in vitro against S. prolificans spores (MICs > 128 μg/ml). In contrast, MICs for PCZ or ICZ in combination with TCR or 17AAG (0.125-0.50 μg/ml) were much lower compared with drug alone. In addition PCZ and ICZ in combination with TCR or 17AAG became fungicidal. Because apoptosis is regulated by the calcineurin pathway in fungi and is under the control of Hsp90, we hypothesized that this synergistic fungicidal effect is mediated via apoptosis. This observed fungicidal activity was mediated by increased apoptosis of S. prolificans germlings, as evidenced by reactive oxygen species accumulation, decreased mitochondrial membrane potential, phosphatidylserine externalization, and DNA fragmentation. Furthermore, induction of caspase-like activity was correlated with TCR or 17AAG + PCZ/ICZ-induced cell death. In conclusion, we report for the first time that PCZ or ICZ in combination with TCR or 17AAG renders S. prolificans exquisitely sensitive to PCZ or ICZ via apoptosis. This finding may stimulate the development of new therapeutic strategies for patients infected with this recalcitrant fungus.

The calcineurin pathway inhibitor tacrolimus enhances the in vitro activity of azoles against Mucorales via apoptosis

The calcineurin pathway regulates antifungal drug resistance and the virulence of several major human-pathogenic fungi, including the recalcitrant Mucorales. We hypothesized that the fungistatic triazoles posaconazole (PCZ) and itraconazole (ICZ) become fungicidal in the setting of the calcineurin inhibitor tacrolimus (TCR) and that such an effect is mediated through apoptosis. Fungicidal activity and apoptosis were studied using standard microbiological techniques and hyphal metabolic and vital dye reduction assays at 37°C in RPMI 1640. Apoptosis was characterized by detecting intracellular Ca(2+), phosphatidylserine (PS) externalization, DNA fragmentation, plasma membrane integrity, chromatin condensation, reactive oxygen species (ROS) generation, caspase-like activity, ATP, and cytochrome c release. MICs for PCZ and ICZ alone were significantly higher (8 to 128 μg/ml) than those of PCZ or ICZ plus TCR (0.25 to 4 μg/ml) for Rhizopus oryzae, Cunninghamella bertholletiae, and Mucor circinelloides. Both PCZ and ICZ in combination with TCR became fungicidal, and their activity was mediated through increased apoptotic cell death of R. oryzae (10 to 50%), C. bertholletiae (5 to 50%), and M. circinelloides (5 to 55%) germlings, with morphological apoptotic changes characterized by externalization of PS, nuclear condensation, and DNA fragmentation. Moreover, activation of the caspase-like activity was correlated with cell death induced by TCR plus PCZ or ICZ. These changes correlated with elevated intracellular Ca(2+) and ROS levels and disturbance of mitochondrial potential. We found that PCZ or ICZ in combination with TCR renders Mucorales sensitive to triazoles via apoptotic death. These observations could serve as a new paradigm for the development of new therapeutic strategies.

Drug combinations against Mucor irregularis in vitro

Combinations of terbinafine or caspofungin with amphotericin B, posaconazole, or itraconazole were studied as potential treatments against 18 isolates of Mucor irregularis in vitro. Synergism of the combinations of terbinafine with amphotericin B, posaconazole, and itraconazole against 38.9, 33.3, and 44.4% of the strains studied was observed. In contrast, synergism of the combinations of caspofungin with amphotericin B, posaconazole, and itraconazole against 99.4, 66.7, and 99.4% of the strains studied was observed. Furthermore, no antagonism was observed.

Tacrolimus enhances the potency of posaconazole against Rhizopus oryzae in vitro and in an experimental model of mucormycosis

BACKGROUND

We hypothesized that tacrolimus, an inhibitor of the calcineurin pathway, would enhance the in vivo activity of posaconazole against Rhizopus oryzae, the Mucorales species most commonly associated with mucormycosis.

METHODS

We examined patterns of growth inhibition and fungicidal activity of posaconazole and tacrolimus, alone and in combination, against R. oryzae in vitro, using multiple methods (ie, hyphal metabolic and fluorescent vital dye reduction assays and measurement of chitin concentrations), and in vivo, using 2 mucormycosis models: an invertebrate model (Drosophila) and a nonlethal murine model of cutaneous mucormycosis.

RESULTS

Combinations of posaconazole and tacrolimus were synergistic in checkerboard assays for 4 clinical isolates of R. oryzae (48-hour fractional inhibitory concentration index, 0.187-0.281). Pharmacodynamic analysis of the combination revealed that the 90% effective concentration threshold of posaconazole activity against R. oryzae could be achieved with 2-fold lower drug concentrations (0.5-1 mg/L) when administered with tacrolimus (0.007-2 mg/L). In vivo, combination therapy was associated with improved survival in the fly model of mucormycosis (65% vs 57% posaconazole alone) and with significant reductions in cutaneous lesions and R. oryzae fungal burden, compared with animals that received posaconazole monotherapy, in the cutaneous model of mucormycosis.

CONCLUSIONS

Combination posaconazole-tacrolimus therapy displays synergism in vitro and improved antifungal efficacy in vivo in 2 phylogenetically distinct models of mucormycosis.

Mucormycosis caused by unusual mucormycetes, non-Rhizopus, -Mucor, and -Lichtheimia species

Rhizopus, Mucor, and Lichtheimia (formerly Absidia) species are the most common members of the order Mucorales that cause mucormycosis, accounting for 70 to 80% of all cases. In contrast, Cunninghamella, Apophysomyces, Saksenaea, Rhizomucor, Cokeromyces, Actinomucor, and Syncephalastrum species individually are responsible for fewer than 1 to 5% of reported cases of mucormycosis. In this review, we provide an overview of the epidemiology, clinical manifestations, diagnosis of, treatment of, and prognosis for unusual Mucormycetes infections (non-Rhizopus, -Mucor, and -Lichtheimia species). The infections caused by these less frequent members of the order Mucorales frequently differ in their epidemiology, geographic distribution, and disease manifestations. Cunninghamella bertholletiae and Rhizomucor pusillus affect primarily immunocompromised hosts, mostly resulting from spore inhalation, causing pulmonary and disseminated infections with high mortality rates. R. pusillus infections are nosocomial or health care related in a large proportion of cases. While Apophysomyces elegans and Saksenaea vasiformis are occasionally responsible for infections in immunocompromised individuals, most cases are encountered in immunocompetent individuals as a result of trauma, leading to soft tissue infections with relatively low mortality rates. Increased knowledge of the epidemiology and clinical presentations of these unusual Mucormycetes infections may improve early diagnosis and treatment.

Identification and susceptibility of Rhizomucor spp. isolated from patients with cutaneous zygomycosis in China

Zygomycosis is a relatively uncommon mycosis with a morbidity that is increasing worldwide. Cutaneous zygomycosis, one of the clinical manifestations of the disease, has also emerged in recent decades. The major reported etiologic agents in China include Rhizomucor spp., Rhizopus spp., Mucor spp., and Lichtheimia spp. (formerly Absidia spp.). This study examined 11 clinical isolates of Rhizomucor that belong to three species (R. variabilis, R. regularior, and R. chlamydosporus). They were identified by both morphological and molecular methods and were found to have a high degree of correlation. In vitro susceptibility of the Rhizomucor isolates to seven antifungal drugs (amphotericin B, itraconazole, terbinafine, voriconazole, fluconazole, flucytosine, and micafungin) were tested, which resulted in amphotericin B being found to be the most active agent against all species evaluated in this study. The investigation also reviewed case reports of cutaneous zygomycosis in China.

Zygomycosis: an emerging fungal infection with new options for management

Zygomycosis occurs primarily in immunosuppressed patients and those with diabetes mellitus. Diabetes remains the most common risk factor; however, zygomycosis has increased among transplant recipients and patients with hematologic malignancy. Treatment or prophylaxis with voriconazole seems to be associated with the development of zygomycosis among severely immunosuppressed patients in these latter risk groups. Rhino-orbital-cerebral zygomycosis is the most common manifestation in patients with diabetes mellitus, but transplant recipients and patients with hematologic malignancy are more likely to develop pulmonary infection. Zygomycosis remains difficult to treat and requires a multifaceted approach involving elimination of predisposing factors, surgical debridement, and antifungal therapy. Lipid formulations of amphotericin B are the treatments of choice. The use of posaconazole has been successful in salvage trials but should not be used as first-line therapy until an effective intravenous formulation is available.

Lipid formulations of amphotericin B as first-line treatment of zygomycosis

Zygomycosis is a difficult to treat and frequently fatal infection affecting immunocompromised and, rarely, immunocompetent patients. The early diagnosis and immediate initiation of treatment with an antifungal agent in combination with surgical intervention has proved critical for the favourable outcome of the disease. Few antifungal agents are available for treatment. Amphotericin B (AmB) deoxycholate has been the drug of choice for many years and is usually given at high daily doses which can result in renal toxicity. Currently, lipid formulations of AmB (liposomal AmB (L-AmB), AmB lipid complex (ABLC), AmB colloidal dispersion (ABCD)), mainly L-AmB, rather than conventional AmB have become the standard therapy. The rationale behind the use of lipid formulations is that they decrease the nephrotoxicity associated with longterm AmB use. Although there is a developing consensus that high doses of lipid formulations of AmB should be the antifungal therapy of choice for all patients with zygomycosis, until now there have been no data available with which to define the appropriate dose. The duration of therapy remains an unresolved issue, regarding both lipid formulations of AmB as well as sequential or combination treatments consisting of lipid formulations of AmB with posaconazole, a drug which has now emerged as a new therapeutic option.

In vitro interactions between antifungals and immunosuppressive drugs against zygomycetes

The in vitro interaction of antifungals with immunosuppressive drugs was evaluated against zygomycetes. The combination of amphotericin B with cyclosporine, rapamycin, or tacrolimus was synergistic for 90%, 70%, and 30% of the isolates, respectively. For posaconazole, itraconazole, and ravuconazole, synergy was more frequently observed with cyclosporine than with rapamycin or tacrolimus and antagonistic interactions were rarely noted. In summary, calcineurin inhibitors and rapamycin can be synergistic in vitro with amphotericin B and azoles against zygomycetes.

Treatment of invasive fungal infections in immunocompromised and transplant patients: AmBiLoad trial and other new data

Opportunistic invasive fungal infections (IFIs) have changed. Moreover, a significantly greater therapeutic armamentarium is now available, with liposomal amphotericin B (L-AmB) administered in new ways, for example in higher doses, in combination with other compounds or inhaled. The objective of this study was to review these three aspects. The AmBiLoad study was designed to clarify whether higher doses of L-AmB could be more efficacious than the licensed dose of 3-5 mg/kg. It was a multicentric study where patients were randomised to receive a 14-day course of 3 mg/kg/day or 10 mg/kg/day L-AmB. A total of 339 patients were enrolled during the study period (April 2003 to October 2004). Discontinuation of treatment, mainly due to adverse events, was frequent (13% in the standard dose group vs. 24% in the high dose group), and only 66% and 50%, respectively, completed 14 days of randomised treatment. There was no statistically significant difference with regard to favourable overall responses between the treatment groups (50% in the standard dose group vs. 46% in the high dose group; P = 0.65). In addition, there was no significant difference according to type of IFI (invasive aspergillosis, 50% vs. 46% in the standard and high dose groups, respectively). The obvious conclusion of this study was that administration of 10 mg/kg/day L-AmB to patients with IFI does not improve efficacy but increases toxicity and price. In vitro and experimental data suggest that the combination of AmB with other antifungal agents may be more effective than monotherapy; however, data regarding the clinical efficacy of L-AmB in combination with other agents are scarce. The use of inhaled L-AmB has shown promising results for use as antifungal prophylaxis in high-risk patients.

Posaconazole enhances the activity of amphotericin B against hyphae of zygomycetes in vitro

The in vitro activity of posaconazole plus amphotericin B against conidia and hyphae of 30 clinical zygomycetes was investigated. The combination of posaconazole with amphotericin B was found to be significantly more synergistic (40%) against hyphae (P < 0.05) than against conidia (10%). Antagonism was not observed.

[In vitro antifungal activity of voriconazole: New data after the first years of clinical experience]

Voriconazole has been developed to meet the increasing need for new and useful antifungal agents for the treatment of invasive mycoses. This review describes the spectrum of voriconazole antifungal activity based on data from in vitro studies published during the last three years. This survey demonstrates that voriconazole has a broad antifungal spectrum against the most common fungal pathogens being its action fungistatic for Candida and fungicidal for Aspergillus and other filamentous fungi. Overall, more than 95% of all Candida isolates tested are susceptible to voriconazole and less than 3% are resistant. Similar or even better activity rates have been described for Aspergillus, Cryptococcus and most of yeasts and moulds of medical importance. We also discuss the limitations related to the azole cross-resistance observed in some Candida glabrata isolates, the poor activity of voriconazole against Scedosporium prolificans, its activity against fungal biofilms and the great potential usefulness of combination of voriconazole with other antifungal drugs.

Combination antifungal therapy: the new frontier

The past decade has seen a significant increase in the incidence of invasive fungal infections. The antifungal armamentarium for the treatment of serious fungal infections remains limited. A possible approach to overcoming antifungal drug resistance and high mortality rates seen in severe fungal infections is to combine two or three classes of antifungals, especially if the drugs have different mechanisms of action. Combinations of new agents along with more traditional antifungals have now been shown to possess some synergistic or at least additive activity against many fungi in in vitro and animal studies. On the other hand, caution is still needed since some antifungal combinations have also demonstrated antagonistic activity. Well-controlled clinical trials are still required to define the most efficacious antifungal regimen. Furthermore, these trials should also evaluate the side-effect potential of combination regimens and the pharmacoeconomic impact these regimens may have.

Invasive zygomycosis: update on pathogenesis, clinical manifestations, and management

Zygomycosis is an increasingly common infection in immunocompromised patients. Advances in the understanding of Zygomycetes pathobiology and the introduction of new drugs with improved activity and tolerability for treatment of zygomycosis have improved the prospects of effectively controlling this devastating infection. Further reductions in mortality will require improved diagnostic and novel therapeutic approaches for this group of aggressive opportunistic molds.

In vitro activities of amphotericin B, caspofungin, itraconazole, posaconazole, and voriconazole against 45 clinical isolates of zygomycetes: comparison of CLSI M38-A, Sensititre YeastOne, and the Etest

We evaluated the activities of amphotericin B, itraconazole, voriconazole, caspofungin, and posaconazole against zygomycetes by CLSI M38-A, Etest and Sensititre. The most active drug was posaconazole, followed by amphotericin B and itraconazole. The correlation of the Etest and Sensititre with CLSI M38-A was moderate for posaconazole but poor for the others.

Voriconazole: a broad spectrum triazole for the treatment of serious and invasive fungal infections

For many years, serious systemic fungal infections have been treated with amphotericin B or narrow-spectrum azole antifungals. These treatments have been effective in many patients, but are associated with tolerability or pharmacokinetic concerns, or suboptimal antifungal activity in some patient groups. Voriconazole is a second-generation triazole with an extended spectrum of activity offering the potential to treat life-threatening fungal infections. The drug is available for intravenous or oral administration and has been shown to be effective in invasive aspergillosis, fluconazole-susceptible and -resistant candidiasis, and infections caused by various other fungal pathogens, including some formerly refractory organisms. Voriconazole is generally well tolerated with transient visual disturbances, liver enzyme abnormalities and skin rashes being the most common adverse events reported, but these rarely lead to treatment discontinuation.

Zygomycosis: the re-emerging fungal infection

Invasive fungal infections are major medical complications in immunocompromised patients. The recent rise in the incidence of cancer and the increased use of newer medical treatment modalities, including organ transplantations, have resulted in growing numbers of highly immunosuppressed individuals. Although aspergillosis and candidiasis are among the most common invasive mycoses in such patients, there is evidence that the incidence of infectious diseases caused by Zygomycetes has risen significantly over the past decade. Patients with diabetes, malignancies, solid organ or bone marrow transplants, or iron overload and those receiving immunosuppressive agents, deferoxamine therapy, or broad-spectrum antimicrobial drugs are at highest risk for zygomycosis. This review details the emergence and importance of zygomycosis in current clinical practice and its manifestations and management. The etiologic species, pathogenesis and risk factors for zygomycosis are reviewed and updated. The clinical spectrum of zygomycosis is now broader, and it can be difficult to distinguish between mucormycosis and enthomophthoramycosis, both of which can manifest as disease ranging from a superficial infection to an angioinvasive infection with high mortality. Finally, the three-part treatment strategy (antifungal drugs, surgery, control of underlying diseases) is reviewed. Lipid formulations of amphotericin B are the antifungal agents of choice for treatment of zygomycosis. A novel antifungal triazole, posaconazole, has been developed and may become approved for treatment of zygomycosis. The clinical experience with adjunctive treatments like colony-stimulating factors, interferon-gamma, and hyperbaric oxygen therapy is still limited.

Peritonitis due to Cunninghamella bertholletiae in a patient undergoing continuous ambulatory peritoneal dialysis

Peritoneal dialysis-associated peritonitis due to fungi of the class Zygomycetes occurs very rarely. A case of fungal continuous ambulatory peritoneal dialysis peritonitis due to Cunninghamella bertholletiae is reported in a 39-year-old Aboriginal woman with end-stage renal failure and diabetes mellitus. This isolate was found to be resistant in vitro to amphotericin B, 5-fluorocytosine, fluconazole, itraconazole, ketoconazole and voriconazole. However, this patient was successfully treated with voriconazole and removal of the Tenckhoff dialysis catheter. Zygomycoses are an emerging threat among immunocompromised patients, including those with chronic renal failure. Zygomycosis due to C. bertholletiae is frequently fatal and is often non-responsive to systemic antifungal therapy. This is believed to be the first reported case of C. bertholletiae causing peritonitis in humans and one of the minority of cases involving this organism with a successful outcome.

A fatal case of disseminated zygomycosis associated with the use of blood glucose self-monitoring equipment

We report a fatal case of disseminated zygomycosis due to Cunninghamella bertholletiae in a 68-year-old man with myelodysplasia and type II diabetes mellitus, receiving desferrioxamine therapy for iron overload secondary to multiple transfusions. It is thought that he acquired the infection through the use of blood glucose self-monitoring equipment.

Combination treatment of invasive fungal infections

The persistence of high morbidity and mortality from systemic fungal infections despite the availability of novel antifungals points to the need for effective treatment strategies. Treatment of invasive fungal infections is often hampered by drug toxicity, tolerability, and specificity issues, and added complications often arise due to the lack of diagnostic tests and to treatment complexities. Combination therapy has been suggested as a possible approach to improve treatment outcome. In this article, we undertake a historical review of studies of combination therapy and also focus on recent studies involving newly approved antifungal agents. The limitations surrounding antifungal combinations include nonuniform interpretation criteria, inability to predict the likelihood of clinical success, strain variability, and variations in pharmacodynamic/pharmacokinetic properties of antifungals used in combination. The issue of antagonism between polyenes and azoles is beginning to be addressed, but data regarding other drug combinations are not adequate for us to draw definite conclusions. However, recent data have identified potentially useful combinations. Standardization of assay methods and adoption of common interpretive criteria are essential to avoid discrepancies between different in vitro studies. Larger clinical trials are needed to assess whether combination therapy improves survival and treatment outcome in the most seriously debilitated patients afflicted with life-threatening fungal infections.

Zygomycosis (mucormycosis): emerging clinical importance and new treatments

PURPOSE OF REVIEW

New importance has been given to zygomycosis, as what was uncommon is no longer. Zygomycosis (mucormycosis) typically occurs in patients with leukemia, with solid-organ transplants or bone marrow transplants, with diabetic ketoacidosis, in those who have received steroids or are neutropenic, and after desferioxamine therapy. Often, both diagnostic and therapeutic measures are performed too late and are inadequate. Mortality rates may be as high as 80% in infected transplant recipients. Zygomycosis also appears to have made a subtle increase in incidence: up to 8% in autopsied patients with leukemia, and 2% in allogenic bone marrow transplant patients. Most infections are acquired by inhalation, ingestion, or trauma. They rapidly infarct blood vessels, resulting in necrosis of surrounding tissue. Over the past few years, new diagnostic procedures, susceptibility tests, and drugs have entered the clinic, and these advances are discussed in the review.

RECENT FINDINGS

With the rise in number of cases of 'zygomycosis', new scrutiny has been directed at the terms 'zygomycosis' and 'mucormycosis'. This review explains their differences and the attending relevance for the clinician. Diagnostic methods include new molecular detection assays and new susceptibility testing options. New treatment options will soon exist with triazole antifungal agents. The first one expected to enter clinical practice is posaconazole in 2005. Its metabolism, pharmacokinetics, in-vitro and in-vivo activity, and clinical study results are described. Finally, we present our approach to zygomycosis.

SUMMARY

This review discusses key elements to laboratory diagnostic and susceptibility procedures and new treatment options.

Combinations of antifungal agents in therapy--what value are they?

Concurrent or sequential antifungal treatment for invasive mycoses has been typically considered as an option to improve results of monotherapy. However, data on the efficacy of combination therapy are sparse and consist largely of results from studies in vitro and experimental animal models. These studies have yielded controversial results depending on the criteria used to evaluate the antifungal interaction. Several combinations that showed synergy in vitro failed to do so in animal models. Overall, apart from cryptococcal infections, combined antifungal therapy is not significantly better than monotherapy in terms of clinical efficacy. It is questionable whether combination therapy should be used in most cases as there is a lack of evidence from well-designed clinical trials. However, combination therapy could be an alternative to monotherapy for patients with invasive infections that are difficult to treat, such as those due to multi-resistant species and for those who fail to respond to standard treatment.