Antifungal activity of colistin against mucorales species in vitro and in a murine model of Rhizopus oryzae pulmonary infection

The Impact of Dimitrios P. Kontoyiannis on Mucormycosis Research

Dimitrios P [...].

Comprehensive Review on the Virulence Factors and Therapeutic Strategies with the Aid of Artificial Intelligence against Mucormycosis

Mucormycosis, a rare but deadly fungal infection, was an epidemic during the COVID-19 pandemic. The rise in cases (COVID-19-associated mucormycosis, CAM) is attributed to excessive steroid and antibiotic use, poor hospital hygiene, and crowded settings. Major contributing factors include diabetes and weakened immune systems. The main manifesting forms of CAM─cutaneous, pulmonary, and the deadliest, rhinocerebral─and disseminated infections elevated mortality rates to 85%. Recent focus lies on small-molecule inhibitors due to their advantages over standard treatments like surgery and liposomal amphotericin B (which carry several long-term adverse effects), offering potential central nervous system penetration, diverse targets, and simpler dosing owing to their small size, rendering the ability to traverse the blood-brain barrier via passive diffusion facilitated by the phospholipid membrane. Adaptation and versatility in mucormycosis are facilitated by a multitude of virulence factors, enabling the pathogen to dynamically respond to various environmental stressors. A comprehensive understanding of these virulence mechanisms is imperative for devising effective therapeutic interventions against this highly opportunistic pathogen that thrives in immunocompromised individuals through its angio-invasive nature. Hence, this Review delineates the principal virulence factors of mucormycosis, the mechanisms it employs to persist in challenging host environments, and the current progress in developing small-molecule inhibitors against them.

Experimental Models to Study the Pathogenesis and Treatment of Mucormycosis

Mucormycosis presents a formidable challenge to clinicians and researchers. Animal models are an essential part of the effort to decipher the pathogenesis of mucormycosis and to develop novel pharmacotherapeutics against it. Diverse model systems have been established, using a range of animal hosts, immune and metabolic perturbations, and infection routes. An understanding of the characteristics, strengths, and drawbacks of these models is needed to optimize their use for specific research aims.

Sequential rearrangement and stereochemical reorganization to design an antimicrobial peptide with enhanced stability

Antimicrobial peptides (AMPs) are natural molecules that function within the innate immune system to counteract pathogenic invasion and minimize the detrimental consequences of infection. However, utilizing these molecules for medical applications has been challenging. In this study, we selected a model AMP with poor stability, Tilapia Piscidin 4 (TP4), and modified its sequence and chirality (TP4-γ) to improve its potential for clinical application. The strategy of chirality inversion was inspired by the cereulide peptide, which has a DDLL enantiomer pattern and exhibits exceptional stability. Sequential substitution of key residues and selective chirality inversion yielded a less toxic peptide with enhanced stability and notable antimicrobial activity. In addition to its superior stability profile and antimicrobial activity, TP4-γ treatment reduced the level of LPS-induced nitric oxide (NO) release in a macrophage cell line. This reduction in NO release may reflect anti-inflammatory properties, as NO is widely known to promote inflammatory processes. Hence, our heterochiral peptide construct shows a more suitable pharmacokinetic profile than its parental compound, and further studies are warranted to develop the molecule for potential clinical application.

A protein-free vaccine stimulates innate immunity and protects against nosocomial pathogens

Traditional vaccines are difficult to deploy against the diverse antimicrobial-resistant, nosocomial pathogens that cause health care-associated infections. We developed a protein-free vaccine composed of aluminum hydroxide, monophosphoryl lipid A, and fungal mannan that improved survival and reduced bacterial burden of mice with invasive blood or lung infections caused by methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, extended-spectrum beta-lactamase-expressing Escherichia coli, and carbapenem-resistant strains of Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The vaccine also conferred protection against the fungi Rhizopus delemar and Candida albicans. Efficacy was apparent by 24 hours and lasted for up to 28 days after a single vaccine dose, with a second dose restoring efficacy. The vaccine acted through stimulation of the innate, rather than the adaptive, immune system, as demonstrated by efficacy in the absence of lymphocytes that were abrogated by macrophage depletion. A role for macrophages was further supported by the finding that vaccination induced macrophage epigenetic alterations that modulated phagocytosis and the inflammatory response to infection. Together, these data show that this protein-free vaccine is a promising strategy to prevent deadly antimicrobial-resistant health care-associated infections.

Virulence traits and novel drug delivery strategies for mucormycosis post-COVID-19: a comprehensive review

The outbreak of a fatal black fungus infection after the resurgence of the cadaverous COVID-19 has exhorted scientists worldwide to develop a nutshell by repurposing or designing new formulations to address the crisis. Patients expressing COVID-19 are more susceptible to Mucormycosis (MCR) and thus fall easy prey to decease accounting for this global threat. Their mortality rates range around 32-70% depending on the organs affected and grow even higher despite the treatment. The many contemporary recommendations strongly advise using liposomal amphotericin B and surgery as first-line therapy whenever practicable. MCR is a dangerous infection that requires an antifungal drug administration on appropriate prescription, typically one of the following: Amphotericin B, Posaconazole, or Isavuconazole since the fungi that cause MCR are resistant to other medications like fluconazole, voriconazole, and echinocandins. Amphotericin B and Posaconazole are administered through veins (intravenously), and isavuconazole by mouth (orally). From last several years so many compounds are developed against invasive fungal disease but only few of them are able to induce effective treatment against the micorals. Adjuvant medicines, more particularly, are difficult to assess without prospective randomized controlled investigations, which are challenging to conduct given the lower incidence and higher mortality from Mucormycosis. The present analysis provides insight into pathogenesis, epidemiology, clinical manifestations, underlying fungal virulence, and growth mechanisms. In addition, current therapy for MCR in Post Covid-19 individuals includes conventional and novel nano-based advanced management systems for procuring against deadly fungal infection. The study urges involving nanomedicine to prevent fungal growth at the commencement of infection, delay the progression, and mitigate fatality risk.

An extensive review on antifungal approaches in the treatment of mucormycosis

During the period of COVID-19, the occurrences of mucormycosis in immunocompromised patients have increased significantly. Mucormycosis (black fungus) is a rare and rapidly progressing fungal infection associated with high mortality and morbidity in India as well as globally. The causative agents for this infection are collectively called mucoromycetes which are the members of the order Mucorales. The diagnosis of the infection needs to be performed as soon as the occurrence of clinical symptoms which differs with types of Mucorales infection. Imaging techniques magnetic resonance imaging or computed tomography scan, culture testing, and microscopy are the approaches for the diagnosis. After the diagnosis of the infection is confirmed, rapid action is needed for the treatment in the form of antifungal therapy or surgery depending upon the severity of the infection. Delaying in treatment declines the chances of survival. In antifungal therapy, there are two approaches first-line therapy (monotherapy) and combination therapy. Amphotericin B (1) and isavuconazole (2) are the drugs of choice for first-line therapy in the treatment of mucormycosis. Salvage therapy with posaconazole (3) and deferasirox (4) is another approach for patients who are not responsible for any other therapy. Adjunctive therapy is also used in the treatment of mucormycosis along with first-line therapy, which involves hyperbaric oxygen and cytokine therapy. There are some drugs like VT-1161 (5) and APX001A (6), Colistin, SCH 42427, and PC1244 that are under clinical trials. Despite all these approaches, none can be 100% successful in giving results. Therefore, new medications with favorable or little side effects are required for the treatment of mucormycosis.

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.

Inhibitory effect of Monascus purpureus pigment extracts against fungi and mechanism of action

The fungus Monascus produces several secondary metabolites of different pigment hues. These pigments have shown various biological activities. In this study, Monascus purpureus pigment extracts were tested (in vitro) against Penicillium expansum MTCC 4900, Rhizopus stolinfer MTCC 10595, and Aspergillus niger MTCC 8652 for antifungal activity. The UV–visible spectrum of M. purpureus fermented rice extracts showed λmax at 395, 425, and 500 nm. This indicated the solubility of yellow, orange, and red pigments in polar-based solvent extraction. The M. purpureus pigment extracts inhibited the radial growth and conidial germination of the test fungi. The fungi treated with pigment extract stained with DiBAC (a vital stain) emitted green fluorescence under a fluorescent microscope. These results indicated that the pigment extracts have affected the membrane potential of the treated fungi. Hence, the fungicidal activity of the pigment extracts is due to the disruption of the cell membrane. The HPLC analysis of the pigment revealed the presence of two major peaks. The UV–visible spectrum corresponding to the HPLC peak at 12-min retention time revealed the presence of orange pigment rubropunctatin. Apparently the rubropunctatin present in the extracts exhibited fungicidal activity. Further studies are warranted to assess the applications of M. purpureus pigments in preventing and treating fungus-related diseases.

Mucormycosis: A hidden mystery of fungal infection, possible diagnosis, treatment and development of new therapeutic agents

Mucormycosis is a fungal infection which got worsens with time if not diagnosed and treated. The current COVID-19 pandemic has association with fungal infection specifically with mucormycosis. Already immunocompromised patients are easy target for COVID-19 and mucormycosis as well. COVID-19 infection imparts in weak immune system so chances of infection is comparatively high in COVID-19 patients. Furthermore, diabetes, corticosteroid medicines, and a weakened immune system are the most prevalent risk factors for this infection as we discussed in case studies here. The steroid therapy for COVID-19 patients sometimes have negative impact on the patient health and this state encounters many infections including mucormycosis. There are treatments available but less promising and less effective. So, researchers are focusing on the promising agents against mucormycosis. It is reported that early treatment with liposomal amphotericin B (AmB), manogepix, echinocandins isavuconazole, posacanazole and other promising therapeutic agents have overcome the burden of mucormycosis. Lipid formulations of AmB have become the standard treatment for mucormycosis due to their greater safety and efficacy. In this review article, we have discussed case studies with the infection of mucormycosis in COVID-19 patients. Furthermore, we focused on anti-mucormycosis agents with mechanism of action of various therapeutics, including coverage of new antifungal agents being investigated as part of the urgent global response to control and combat this lethal infection, especially those with established risk factors.

Focusing COVID-19-associated mucormycosis: a major threat to immunocompromised COVID-19

COVID-19 disease has been identified to cause remarkable increase of mucormycosis infection cases in India, with the majority of cases being observed in individuals recovering from COVID-19. Mucormycosis has emanated as an outcome of the recent COVID-19 pandemic outbreak as rapidly developing fatal illness which was acquired by Mucorales fungus which is a subcategory of molds known as mucormycetes. Mucormycosis is one of the serious, sporadic mycotic illnesses which is a great threat to immunocompromised COVID-19 patients and affects people of all ages, including children with COVID-19 infections. This is associated with tissue damaging property and, therefore, causes serious clinical complications and elevated death rate. The COVID-19-associated mucormycosis or "black fungus" are the terms used interchangeably. The rapid growth of tissue necrosis presenting as "rhino-orbital-cerebral, pulmonary, cutaneous, gastrointestinal, and disseminated disease" are various clinical forms of mucormycosis. The patient's prognosis and survival can be improved with proper surgeries using an endoscopic approach for local tissue protection in conjunction with course of appropriate conventional antifungal drug like Amphotericin-B and novel drugs like Rezafungin, encochleated Amphotericin B, Orolofim, and SCY-078 which have been explored in last few years. This review provides an overview of mucormycosis including its epidemiology, pathophysiology, risk factors, its clinical forms, and therapeutic approaches for disease management like antifungal therapy, surgical debridement, and iron chelators. The published patents and ongoing clinical trials related to mucormycosis have also been mentioned in this review.

Mucormycosis in the COVID-19 Environment: A Multifaceted Complication

The second wave of coronavirus disease 2019 (COVID-19) caused severe infections with high mortality. An increase in the cases of COVID-19-associated mucormycosis (CAM) was reported predominantly in India. Commonly present in immunocompromised individuals, mucormycosis is often a life-threatening condition. Confounding factors and molecular mechanisms associated with CAM are still not well understood, and there is a need for careful research in this direction. In this review, a brief account of the diagnosis, management, and advancement in drug discovery for mucormycosis has been provided. Here, we summarize major factors that dictate the occurrence of mucormycosis in COVID-19 patients through the analysis of published literature and case reports. Major predisposing factors to mucormycosis appear to be uncontrolled diabetes, steroid therapy, and certain cancers. At the molecular level, increased levels of iron in COVID-19 might contribute to mucormycosis. We have also discussed the potential role and regulation of iron metabolism in COVID-19 patients in establishing fungal growth. Other factors including diabetes prevalence and fungal spore burden in India as contributing factors have also been discussed.

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.

In Vitro Activity of Amphotericin B in Combination with Colistin against Fungi Responsible for Invasive Infections

The in vitro interaction of amphotericin B in combination with colistin was evaluated against a total of 86 strains comprising of 47 Candida species (10 Candida albicans, 15 Candida auris, five Candida glabrata, three Candida kefyr, five Candida krusei, four Candida parapsilosis and five Candida tropicalis), 29 Aspergillus species (five Aspergillus flavus, 10 Aspergillus fumigatus, four Aspergillus nidulans, five Aspergillus niger, and five Aspergillus terreus), and 10 Rhizopus species (seven Rhizopus arrhizus, one Rhizopus delemar and two Rhizopus microsporus) strains. For the determination of the interaction, a microdilution checkerboard technique based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) reference method for antifungal susceptibility testing was used. Results of the checkerboard technique were evaluated by the fractional inhibitory concentration index (FICI) based on the Loewe additivity model for all isolates. Different inhibition endpoints were used to capture both the interaction at MIC and sub-MIC levels. Additionally, checkerboard technique results for Candida species were evaluated by response surface analysis based on the Bliss independence model. Against common Candida species, the combination was synergistic for 75% of the strains by FICI and for 66% of the strains by response surface analysis. For C. tropicalis, the interaction was antagonistic for three isolates by FICI, but antagonism was not confirmed by response surface analysis. Interestingly, synergistic and antagonistic FICIs were simultaneously present on checkboard microplates of all three strains. Against C. auris the combination was synergistic for 73% of the strains by response surface analysis and for 33% of the strains by FICI. This discrepancy could be related to the insensitivity of the FICI to detect weak interactions. Interaction for all other strains was indifferent. For Aspergillus and Rhizopus species combination exhibited only indifferent interactions against all tested strains.

Mucormycosis Amid COVID-19 Crisis: Pathogenesis, Diagnosis, and Novel Treatment Strategies to Combat the Spread

The havoc unleashed by COVID-19 pandemic has paved way for secondary ominous fungal infections like Mucormycosis. It is caused by a class of opportunistic pathogens from the order Mucorales. Fatality rates due to this contagious infection are extremely high. Numerous clinical manifestations result in damage to multiple organs subject to the patient's underlying condition. Lack of a proper detection method and reliable treatment has made the management of this infection troublesome. Several reports studying the behavior pattern of Mucorales inside the host by modulation of its defense mechanisms have helped in understanding the pathogenesis of this angio-invasive infection. Many recent advances in diagnosis and treatment of this fungal infection have not been much beneficial. Therefore, there is a need to foster more viable strategies. This article summarizes current and imminent approaches that could aid effective management of these secondary infections in these times of global pandemic. It is foreseen that the development of newer antifungal drugs, antimicrobial peptides, and nanotechnology-based approaches for drug delivery would help combat this infection and curb its spread.

Investigating Factors of False-Positive Results of Aspergillus Galactomannan Assay: A Case-Control Study in Intensive Care Units

Background: Studies on false-positive galactomannan (GM) enzyme immunoassay (EIA) results and treatment for critically ill patients are scarce. Objectives: The study aimed to determine the false-positive rate of GM-EIA and to probe the risk factors of false positivity among patients in the intensive care units (ICUs). Methods: A case-control approach was conducted to review adult patients who had at least one GM-EIA result and were admitted to the ICU. Those who had no fungal culture were excluded. The clinical characteristics and critical care between patients with false-positive and true-negative GM index (GMI) were compared. Results: Of 206 patients enrolled and with GM-EIA results, 20 (9.7%) were considered to have false-positive antigenemia, including 9 in bronchoalveolar lavages (BAL) and 11 in serum. A total of 148 (71.8%) were true-negatives. After paired grouping of 1:4, factors researched in the previous studies showed no significant difference. However, compared with the true-negatives, patients with positive GM test results but were incompatible with the diagnosis of invasive aspergillosis were more prone to the risk of false positivity due to the use of colistin inhalation. It seemed to be the only factor that significantly increased the risk of false positivity after multivariate analysis (adjusted odds ratio, 35.68; 95% CI, 3.77-337.51, p = 0.002). Conclusions: Colistin inhalation treatment may contribute to false-positive GM-EIA results. The positive GMI among patients receiving colistin nebulization should be interpreted with caution.

Influence of iron on growth and on susceptibility to itraconazole in Sporothrix spp

We evaluated the growth and the susceptibility to oxidative stress of Sporothrix spp., exposed to different iron concentrations in culture medium, and the susceptibility of Sporothrix spp. to itraconazole, alone and in combination with to the iron chelator deferasirox. The results showed that the growth of S. brasiliensis isolates was more affected by iron availability in comparison to S. schenckii, but both fungal species conidia became more prone to oxidative stress when iron was added to culture medium. Conversely, the combination of itraconazole and deferasirox only resulted in synergism against a minority of S. schenckii isolates.

In vitro synergy of isavuconazole in combination with colistin against Candida auris

The in vitro interactions of isavuconazole with colistin were evaluated against 15 clinical Candida auris isolates by a microdilution checkerboard technique based on the EUCAST reference method for antifungal susceptibility testing and by agar diffusion using isavuconazole gradient concentration strips with or without colistin incorporated RPMI agar. Interpretation of the checkerboard results was done by the fractional inhibitory concentration index and by response surface analysis based on the Bliss model. By checkerboard, combination was synergistic for 93% of the isolates when interpretation of the data was done by fractional inhibitory concentration index, and for 80% of the isolates by response surface analysis interpretation. By agar diffusion test, although all MICs in combination decreased compared to isavuconazole alone, only 13% of the isolates met the definition of synergy. Essential agreement of EUCAST and gradient concentration strip MICs at +/− 2 log₂ dilutions was 93.3%. Antagonistic interactions were never observed for any technique or interpretation model used.

Colistin and Isavuconazole Interact Synergistically In Vitro against Aspergillus nidulans and Aspergillus niger

The in vitro interactions of isavuconazole in combination with colistin were evaluated against 55 clinical Aspergillus species isolates belonging to the five most important species (Aspergillus flavus, Aspergillus fumigatus, Aspergillus nidulans, Aspergillus niger, and Aspergillus terreus) responsible for human aspergillosis by a microdilution checkerboard technique based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) reference method for antifungal susceptibility testing. Selected isolates (A. nidulans, n = 10; A. niger, n = 15) were additionally evaluated by an agar diffusion assay using isavuconazole gradient concentration strips with or without colistin incorporated Roswell Parc Memorial Institute (RPMI) agar. Interpretation of the checkerboard results was done by the fractional inhibitory concentration index. Using the checkerboard method, combination isavuconazole-colistin was synergistic for 100% of the 15 A. nidulans isolates and for 60% of the 20 A. niger isolates. No interactions were found for any of the other isolates. By agar diffusion assay, minimal inhibitory concentrations (MICs) in combination decreased compared to isavuconazole alone for 92% of the isolates. No interactions were found for any A. nidulans isolates, but synergy was observed for 40% of the A. niger isolates. A poor essential agreement of EUCAST and gradient concentration strip MICs at ± 2 log2 dilutions with 0% was obtained. Antagonistic interactions were never observed regardless of the technique used.

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.

Therapeutic Challenges of Non-Aspergillus Invasive Mold Infections in Immunosuppressed Patients

While Aspergillus spp. remain the major cause of invasive mold infections in hematologic cancer patients and transplant recipients, other opportunistic molds, such as Mucorales, Fusarium, and Scedosporium spp. are increasingly encountered in an expanding population of patients with severe and prolonged immunosuppression. High potential for tissue invasion and dissemination, resistance to multiple antifungals and high mortality rates are hallmarks of these non-Aspergillus invasive mold infections (NAIMIs). Assessment of drug efficacy is particularly difficult in the complex treatment scenarios of NAIMIs. Specifically, correlation between in vitro susceptibility and in vivo responses to antifungals is hard to assess, in view of the multiple, frequently interrelated factors influencing outcomes, such as pharmacokinetic/pharmacodynamic parameters determining drug availability at the site of infection, the net state of immune suppression, delay in diagnosis, or surgical debulking of infectious foci. Our current therapeutic approach of NAIMIs should evolve toward a better integration of the dynamic interactions between the pathogen, the drug and the host. Innovative concepts of experimental research may consist in manipulating the host immune system to induce a specific antifungal response or targeted drug delivery. In this review, we discuss the challenges in the management of NAIMIs and provide an update about the latest advances in diagnostic and therapeutic approaches.

Anti-Candida activity of existing antibiotics and their derivatives when used alone or in combination with antifungals

Fungal infections are a growing challenge in immunocompromised patients, especially candidiasis. The prolonged use of traditional antifungals to treat Candida infection has caused the emergence of drug resistance, especially fluconazole. Therefore, new therapeutic strategies for Candida infection are warranted. Recently, attention has been paid to the anti-Candida activity of antibiotics and their derivatives. Studies revealed that a series of antibiotics/derivatives displayed potential anti-Candida activity and some of them could significantly increase the susceptibility of antifungals. Interestingly, the derivatives of aminoglycosides were even more active than fluconazole/itraconazole/posaconazole. This article reviews the anti-Candida activities and mechanisms of antibiotics/derivatives used alone or in combination with antifungals. This review will helpfully provide novel insights for overcoming Candida resistance and discovering new antifungals.

In vitro polymyxin activity against clinical multidrug-resistant fungi

Background

Although antifungals are available and usually used against fungal infections, multidrug-resistant (MDR) fungal pathogens are a growing problem for public health. Moreover, fungal infections have become more prevalent nowadays due to the increasing number of people living with immunodeficiency. Thus, previously rarely-isolated and/or unidentified fungal species including MDR yeast and moulds have emerged around the world. Recent works indicate that polymyxin antibiotics (polymyxin B and colistin) have potential antifungal proprieties. Therefore, investigating the in vitro activity of these molecules against clinical multidrug-resistant yeast and moulds could be very useful.

Methods

In this study, a total of 11 MDR yeast and filamentous fungal strains commonly reported in clinical settings were tested against polymyxin antibiotics. These include strains belonging to the Candida, Cryptococcus and Rhodotorula yeast genera, along with others belonging to the Aspergillus, Fusarium, Scedosporium, Lichtheimia and Rhizopus mould genera. The fungicidal or fungistatic action of colistin against clinical yeast strains was determined by the time-kill study. Further, a checkerboard assay for its combination with antifungal agents, usually used in clinical practices (amphotericin B, itraconazole, voriconazole), was carried out against multi-drug resistant fungal strains.

Results

Polymyxin B and colistin exhibited an antifungal activity against all MDR fungal strains tested with MICs ranging from 16 to 128 μg/ml, except for the Aspergillus species. In addition, colistin has a fungicidal action against yeast species, with minimum fungicidal concentrations ranging from 2 to 4 times MICs. It induces damage to the MDR Candida albicans membrane. A synergistic activity of colistin-amphotericin B and colistin-itraconazole associations against Candida albicans and Lichtheimia corymbifera strains, respectively, and colistin-fluconazole association against Rhodotorula mucilaginosa, was demonstrated using a checkerboard microdilution assay.

Conclusion

colistin could be proposed, in clinical practice, in association with other antifungals, to treat life-threatening fungal infections caused by MDR yeasts or moulds.

Animal Models to Study Mucormycosis

Mucormycosis is a rare but often fatal or debilitating infection caused by a diverse group of fungi. Animal models have been crucial in advancing our knowledge of mechanisms influencing the pathogenesis of mucormycoses, and to evaluate therapeutic strategies. This review describes the animal models established for mucormycosis, summarizes how they have been applied to study mucormycoses, and discusses the advantages and limitations of the different model systems.

Skull Base Mucormycosis in an Immunocompetent Patient: A Case Report and Literature Review

To demonstrate the affection of skull base by mucormycosis in an immunocompetent individual. Mucormycosis is an opportunistic infection principally seen in immunocompromised individuals, but recently being increasingly recognized in otherwise healthy individuals. Skull base involvement secondary to otogenic nidus, mimicking otitis media was rarely reported. A 34 year-old male, an otherwise healthy patient presented with facial nerve palsy followed by trismus, neck swelling and neck stiffness. Radical mastoidectomy with tympanoplasty and Facial nerve decompression along with Endoscopic guided debridement of sinuses and pterygopalatine fossa followed by medical treatment for 14 weeks. Facial nerve functioning, dry ear canal and relief from other symptoms. Surgical debridement and post op Anti fungal treatment improved the facial nerve function to House brackmann grade-II and also provided relief from trismus and stiffness and improved the overall general condition of the patient. Mucor is a saprophytic organism, which can cause extensive progression, regardless of the immune status. To the best of our knowledge, this is one of the very few rare cases that have been reported in the context of skull base mucormycosis in immunocompetent individuals. Surgical debridement followed by anti fungal therapy continues to remain the mainstay of treatment.

Recent advances and perspectives in the design and development of polymyxins

Covering: 1947-early 2017, particularly from 2005-early 2017The rise of bacterial pathogens with acquired resistance to almost all available antibiotics is becoming a serious public health issue. Polymyxins, antibiotics that were mostly abandoned a few decades ago because of toxicity concerns, are ultimately considered as a last-line therapy to treat infections caused by multi-drug resistant Gram-negative bacteria. This review surveys the progress in understanding polymyxin structure, and their chemistry, mechanisms of antibacterial activity and nephrotoxicity, biomarkers, synergy and combination with other antimicrobial agents and antibiofilm properties. An update of recent efforts in the design and development of a new generation of polymyxin drugs is also discussed. A novel approach considering the modification of the scaffold of polymyxins to integrate metabolism and detoxification issues into the drug design process is a promising new line to potentially prevent accumulation in the kidneys and reduce nephrotoxicity.

New Horizons in Antifungal Therapy

Recent investigations have yielded both profound insights into the mechanisms required by pathogenic fungi for virulence within the human host, as well as novel potential targets for antifungal therapeutics. Some of these studies have resulted in the identification of novel compounds that act against these pathways and also demonstrate potent antifungal activity. However, considerable effort is required to move from pre-clinical compound testing to true clinical trials, a necessary step toward ultimately bringing new drugs to market. The rising incidence of invasive fungal infections mandates continued efforts to identify new strategies for antifungal therapy. Moreover, these life-threatening infections often occur in our most vulnerable patient populations. In addition to finding completely novel antifungal compounds, there is also a renewed effort to redirect existing drugs for use as antifungal agents. Several recent screens have identified potent antifungal activity in compounds previously indicated for other uses in humans. Together, the combined efforts of academic investigators and the pharmaceutical industry is resulting in exciting new possibilities for the treatment of invasive fungal infections.

Micafungin triggers caspase-dependent apoptosis in Candida albicans and Candida parapsilosis biofilms, including caspofungin non-susceptible isolates

Candida biofilms play an important role in infections associated with medical devices and are resistant to antifungals. We hypothesized that the echinocandin micafungin (MICA) exerts an enhanced antifungal activity against caspofungin (CAS)-susceptible (CAS-S) and CAS-non-susceptible (CAS-NS) Candida albicans and Candida parapsilosis which is at least in part through apoptosis, even in the biofilm environment. Apoptosis was characterized by detecting reactive oxygen species (ROS) accumulation, depolarization of mitochondrial membrane potential (MMP), DNA fragmentation, lack of plasma membrane integrity, and metacaspase activation following exposure of Candida biofilm to MICA for 3h at 37°C in RPMI 1640 medium. The minimum inhibitory concentration was higher for CAS (2.0-16.0 μg/mL) than for MICA (1.0-8.0 μg/mL) for Candida biofilms. Elevated intracellular ROS levels and depolarization of MMP was evident in CAS-S C. albicans (3.0-4.2 fold) and C. parapsilosis (4.8-5.4 fold) biofilms compared with CAS-NS (1.2 fold) after exposure to MICA (0.25x-1xMIC). Elevated intracellular ROS levels and depolarization of MMP was evident in CAS-S C. albicans (3.0-4.2 fold) and C. parapsilosis (4.8-5.4 fold) biofilms compared with CAS-NS (1.2 fold) after exposure to MICA (0.25x-1xMIC). Finally higher ß-1, 3 glucan levels were seen in sessile cells compared to planktonic cells, especially in CAS-NS strains. MICA treatment might induce a metacaspase-dependent apoptotic process in biofilms of both CAS-S C. albicans and C. parapsilosis, and to some degree in CAS-NS strains.

Biofilm Filtrates of Pseudomonas aeruginosa Strains Isolated from Cystic Fibrosis Patients Inhibit Preformed Aspergillus fumigatus Biofilms via Apoptosis

Pseudomonas aeruginosa (Pa) and Aspergillus fumigatus (Af) colonize cystic fibrosis (CF) patient airways. Pa culture filtrates inhibit Af biofilms, and Pa non-CF, mucoid (Muc-CF) and nonmucoid CF (NMuc-CF) isolates form an ascending inhibitory hierarchy. We hypothesized this activity is mediated through apoptosis induction. One Af and three Pa (non-CF, Muc-CF, NMuc-CF) reference isolates were studied. Af biofilm was formed in 96 well plates for 16 h ± Pa biofilm filtrates. After 24 h, apoptosis was characterized by viability dye DiBAc, reactive oxygen species (ROS) generation, mitochondrial membrane depolarization, DNA fragmentation and metacaspase activity. Muc-CF and NMuc-CF filtrates inhibited and damaged Af biofilm (p<0.0001). Intracellular ROS levels were elevated (p<0.001) in NMuc-CF-treated Af biofilms (3.7- fold) compared to treatment with filtrates from Muc-CF- (2.5- fold) or non-CF Pa (1.7- fold). Depolarization of mitochondrial potential was greater upon exposure to NMuc-CF (2.4-fold) compared to Muc-CF (1.8-fold) or non-CF (1.25-fold) (p<0.0001) filtrates. Exposure to filtrates resulted in more DNA fragmentation in Af biofilm, compared to control, mediated by metacaspase activation. In conclusion, filtrates from CF-Pa isolates were more inhibitory against Af biofilms than from non-CF. The apoptotic effect involves mitochondrial membrane damage associated with metacaspase activation.

Iron starvation induces apoptosis in Rhizopus oryzae in vitro

Mortality associated with mucormycosis remains high despite current antifungals. Iron-starvation strategies have been shown to have promising activity against Mucorales. We hypothesized that iron starvation enhances apoptosis in Rhizopus oryzae. Apoptosis was characterized in R. oryzae transformed with RNAi plasmid targeting FTR1 expression (iron permease mutant) or empty plasmid grown in iron rich (0.125% FeCl3) and iron depleted media (YNB+1mM ferrozine and 1 mM ascorbic acid). Increased apoptosis was observed with dihydrorhodamine-123 and rhodamine-123 staining in the iron starved mutant FTR1 when compared to empty plasmid, followed by increased extracellular ATP levels. In addition, DNA fragmentation and metacaspase activity were prominent in FTR1. In contrast, Rhizopus strains grown in iron-rich medium displayed minimal apoptosis. Our results demonstrate a metacaspase dependent apoptotic process in iron deprived condition and further support the role of iron starvation strategies as an adjunct treatment for mucormycosis, a mechanism by which iron starvation affects R. oryzae.

Micafungin induced apoptosis in Candida parapsilosis independent of its susceptibility to micafungin

We hypothesized that the cell wall inhibitor micafungin (MICA) induces apoptosis in both MICA-susceptible (MICA-S) and MICA-non-susceptible (MICA-NS) Candida parapsilosis. Antifungal activity and apoptosis were analyzed in MICA-S and MICA-NS C. parapsilosis strains following exposure to micafungin for 3 h at 37°C in RPMI 1640 medium. Apoptosis was characterized by detecting phosphatidylserine externalization (PS), plasma membrane integrity, reactive oxygen species (ROS) generation, mitochondrial membrane potential changes, adenosine triphosphate (ATP) release, and caspase-like activity. Apoptosis was detected in MICA exposed (0.25 to 1 mg/L) susceptible C. parapsilosis strains and was associated with apoptosis of 20-52% of analyzed cells versus only 5-30% of apoptosis in MICA-NS cells exposed to micafungin (0.5 to 2 mg/L; P = 0.001). The MICA antifungal activity was correlated with apoptotic cells showing increased dihydrorhodamine-123 staining (indicating ROS production), Rh-123 staining (decreased mitochondrial membrane potential), elevated ATP, and increased metacaspase activity. In conclusion, MICA is pro-apoptotic in MICA-S cells, but still exerts apoptotic effects in MICA -NS C. parapsilosis.

Polymyxin B versus colistin: an update

Polymyxin B and colistin (polymyxin E) are polypeptide antibiotics that were developed in the 1940s, but fell into disfavor due to their high toxicity rates. These two antibiotics were previously regarded to be largely equivalent, due to similarities in their chemical structure and spectrum of activity. In recent years, several pertinent differences, especially in terms of potency and disposition, have been revealed between polymyxin B and colistin. These differences are mainly attributed to the fact that polymyxin B is administered parenterally in its active form, while colistin is administered parenterally as an inactive pro-drug, colistimethate. In this review, we summarize the similarities and differences between polymyxin B and colistin. We also discuss the potential clinical implications of these findings, and provide our perspectives on how polymyxins should be employed to preserve their utility in this era of multi-drug resistance.

Successful treatment of Batrachochytrium salamandrivorans infections in salamanders requires synergy between voriconazole, polymyxin E and temperature

Chytridiomycosis caused by the chytrid fungus Batrachochytrium salamandrivorans (Bsal) poses a serious threat to urodelan diversity worldwide. Antimycotic treatment of this disease using protocols developed for the related fungus Batrachochytrium dendrobatidis (Bd), results in therapeutic failure. Here, we reveal that this therapeutic failure is partly due to different minimum inhibitory concentrations (MICs) of antimycotics against Bsal and Bd. In vitro growth inhibition of Bsal occurs after exposure to voriconazole, polymyxin E, itraconazole and terbinafine but not to florfenicol. Synergistic effects between polymyxin E and voriconazole or itraconazole significantly decreased the combined MICs necessary to inhibit Bsal growth. Topical treatment of infected fire salamanders (Salamandra salamandra), with voriconazole or itraconazole alone (12.5 μg/ml and 0.6 μg/ml respectively) or in combination with polymyxin E (2000 IU/ml) at an ambient temperature of 15 °C during 10 days decreased fungal loads but did not clear Bsal infections. However, topical treatment of Bsal infected animals with a combination of polymyxin E (2000 IU/ml) and voriconazole (12.5 μg/ml) at an ambient temperature of 20 °C resulted in clearance of Bsal infections. This treatment protocol was validated in 12 fire salamanders infected with Bsal during a field outbreak and resulted in clearance of infection in all animals.

Complex interaction of deferasirox and Pythium insidiosum: iron-dependent attenuation of growth in vitro and immunotherapy-like enhancement of immune responses in vivo

Pythium insidiosum iron acquisition mechanisms are unknown. We previously showed that the iron chelator deferasirox had weak activity in vitro and in rabbits with experimental pythiosis. Here we show that deferasirox causes damage to P. insidiosum hyphae in vitro, but that activity is diminished in the presence of exogenous iron. The tissue activity of the proinflammatory enzyme adenosine deaminase and the histological pattern observed in pythiosis lesions of rabbits treated with deferasirox were similar to the ones in animals treated with immunotherapy.

Gastrointestinal mucormycosis requiring surgery in adults with hematologic malignant tumors: literature review

BACKGROUND

Gastrointestinal mucormycosis is associated with high mortality rates. Appropriate and early antifungal therapy and prompt surgical intervention are essential.

METHOD

Case report and literature review.

RESULTS

Nineteen case reports were reviewed describing adults with hematologic malignant tumors who developed intestinal mucormycosis and underwent surgery. The overall survival rate was 50%.

CONCLUSION

Intestinal mucormycosis is an infection associated with a high mortality rate although adults with underlying hematologic malignant have improved outcomes compared with other groups.

An antimicrobial peptidomimetic induces Mucorales cell death through mitochondria-mediated apoptosis

The incidence of mucormycosis has dramatically increased in immunocompromised patients. Moreover, the array of cellular targets whose inhibition results in fungal cell death is rather limited. Mitochondria have been mechanistically identified as central regulators of detoxification and virulence in fungi. Our group has previously designed and developed a proteolytically-resistant peptidomimetic motif D(KLAKLAK)2 with pleiotropic action ranging from targeted (i.e., ligand-directed) activity against cancer and obesity to non-targeted activity against antibiotic resistant gram-negative rods. Here we evaluated whether this non-targeted peptidomimetic motif is active against Mucorales. We show that D(KLAKLAK)2 has marked fungicidal action, inhibits germination, and reduces hyphal viability. We have also observed cellular changes characteristic of apoptosis in D(KLAKLAK)2-treated Mucorales cells. Moreover, the fungicidal activity was directly correlated with vacuolar injury, mitochondrial swelling and mitochondrial membrane depolarization, intracellular reactive oxygen species accumulation (ROS), and increased caspase-like enzymatic activity. Finally, these apoptotic features were prevented by the addition of the ROS scavenger N-acetyl-cysteine indicating mechanistic pathway specificity. Together, these findings indicate that D(KLAKLAK)2 makes Mucorales exquisitely susceptible via mitochondrial injury-induced apoptosis. This prototype may serve as a candidate drug for the development of translational applications against mucormycosis and perhaps other fungal infections.

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.

Aspergillus fumigatus hyphal damage caused by noninvasive radiofrequency field-induced hyperthermia

We studied the effect of noninvasive radiofrequency-induced hyperthermia on the viability of Aspergillus fumigatus hyphae in vitro. Radiofrequency-induced hyperthermia resulted in significant (>70%, P < 0.0001) hyphal damage in a time and thermal dose-dependent fashion as assessed by XTT [(sodium 2,3,-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)-carbonyl] (1)-2H-tetrazolium inner salt)], DiBAC [bis-(1,3-dibutylbarbituric acid) trimethine oxonol] staining, and transmission electron microscopy. For comparison, water bath hyperthermia was used over the range of 45 to 55°C to study hyphal damage. Radiofrequency-induced hyperthermia resulted in severe damage to the outer fibrillar layer of hyphae at a shorter treatment time compared to water bath hyperthermia. Our preliminary data suggest that radiofrequency-induced hyperthermia might be an additional therapeutic approach to use in the management of mold infections.

Hyperthermia sensitizes Rhizopus oryzae to posaconazole and itraconazole action through apoptosis

The high mortality rate of mucormycosis with currently available monotherapy has created interest in studying novel strategies for antifungal agents. With the exception of amphotericin B (AMB), the triazoles (posaconazole [PCZ] and itraconazole [ICZ]) are fungistatic in vitro against Rhizopus oryzae . We hypothesized that growth at a high temperature (42°C) results in fungicidal activity of PCZ and ICZ that is mediated through apoptosis. R. oryzae had high MIC values for PCZ and ICZ (16 to 64 μg/ml) at 25°C; in contrast, the MICs for PCZ and ICZ were significantly lower at 37°C (8 to 16 μg/ml) and 42°C (0.25 to 1 μg/ml). Furthermore, PCZ and ICZ dose-dependent inhibition of germination was more pronounced at 42°C than at 37°C. In addition, intracellular reactive oxygen species (ROS) increased significantly when fungi were exposed to antifungals at 42°C. Characteristic cellular changes of apoptosis in R. oryzae were induced by the accumulation of intracellular reactive oxygen species. Cells treated with PCZ or ICZ in combination with hyperthermia (42°C) exhibited characteristic markers of early apoptosis: phosphatidylserine externalization visualized by annexin V staining, membrane depolarization visualized by bis-[1,3-dibutylbarbituric acid] trimethine oxonol (DiBAC) staining, and increased metacaspase activity. Moreover, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay and DAPI (4',6-diamidino-2-phenylindole) staining demonstrated DNA fragmentation and condensation, respectively. The addition of N-acetylcysteine increased fungal survival, prevented apoptosis, reduced ROS accumulation, and decreased metacaspase activation. We concluded that hyperthermia, either alone or in the presence of PCZ or ICZ, induces apoptosis in R. oryzae. Local thermal delivery could be a therapeutically useful adjunct strategy for these refractory infections.

Mitochondrial respiratory pathways inhibition in Rhizopus oryzae potentiates activity of posaconazole and itraconazole via apoptosis

The incidence of mucormycosis has increased drastically in immunocompromised patients. Also the array of targets whose inhibition results in Mucorales death is limited. Recently, researchers identified mitochondria as important regulators of detoxification and virulence mechanisms in fungi. In this context, targeting the mitochondrial respiratory chain may provide a new platform for antifungal development. We hypothesized that targeting respiratory pathways potentiates triazoles activity via apoptosis. We found that simultaneous administration of antimycin A (AA) and benzohydroxamate (BHAM), inhibitors of classical and alternative mitochondrial pathways respectively, resulted in potent activity of posaconazole (PCZ) and itraconazole (ICZ) against Rhizopus oryzae. We observed cellular changes characteristic of apoptosis in R. oryzae cells treated with PCZ or ICZ in combination with AA and BHAM. The fungicidal activity of this combination against R. oryzae was correlated with intracellular reactive oxygen species accumulation (ROS), phosphatidylserine externalization, mitochondrial membrane depolarization, and increased caspase like activity. DNA fragmentation and condensation assays also revealed apoptosis of R. oryzae cells. These apoptotic features were prevented by the addition of the ROS scavenger N-acetyl-cysteine. Taken together, these findings suggest that the use of PCZ or ICZ in combination with AA and BHAM makes R. oryzae exquisitely sensitive to treatment with triazoles via apoptosis. This strategy may serve as a new model for the development of improved or novel antifungal agents.

Synergy of the antibiotic colistin with echinocandin antifungals in Candida species

OBJECTIVES

Candida albicans is the most prevalent fungal pathogen of humans, causing a wide range of infections from harmless superficial to severe systemic infections. Improvement of the antifungal arsenal is needed since existing antifungals can be associated with limited efficacy, toxicity and antifungal resistance. Here we aimed to identify compounds that act synergistically with echinocandin antifungals and that could contribute to a faster reduction of the fungal burden.

METHODS

A total of 38 758 compounds were tested for their ability to act synergistically with aminocandin, a β-1,3-glucan synthase inhibitor of the echinocandin family of antifungals. The synergy between echinocandins and an identified hit was studied with chemogenomic screens and testing of individual Saccharomyces cerevisiae and C. albicans mutant strains.

RESULTS

We found that colistin, an antibiotic that targets membranes in Gram-negative bacteria, is synergistic with drugs of the echinocandin family against all Candida species tested. The combination of colistin and aminocandin led to faster and increased permeabilization of C. albicans cells than either colistin or aminocandin alone. Echinocandin susceptibility was a prerequisite to be able to observe the synergy. A large-scale screen for genes involved in natural resistance of yeast cells to low doses of the drugs, alone or in combination, identified efficient sphingolipid and chitin biosynthesis as necessary to protect S. cerevisiae and C. albicans cells against the antifungal combination.

CONCLUSIONS

These results suggest that echinocandin-mediated weakening of the cell wall facilitates colistin targeting of fungal membranes, which in turn reinforces the antifungal activity of echinocandins.

Evaluation of the anticryptococcal activity of the antibiotic polymyxin B in vitro and in vivo

Polymyxin B (PMB), a cationic lipid oligopeptide used to treat Gram-negative bacterial infections, was previously identified to possess broad-spectrum antifungal activity and to work synergistically with azole antifungals in vitro. Here we evaluated the efficacy of PMB against Cryptococcus neoformans in vitro and in vivo and explored the mechanism of the hypersensitivity of this fungus to this compound. Using comparative time-course assays, PMB was found to kill both proliferative and quiescent cryptococcal cells in vitro. Presence of the polysaccharide capsule, a characteristic feature of Cryptococcus, significantly enhances the susceptibility of this fungus to the fungicidal activity of PMB. Furthermore, PMB is able to reduce the tissue fungal burden both in intravenous and inhalation models of murine cryptococcosis at a level comparable with the commonly used antifungal fluconazole. These findings suggest that PMB could provide an additional option for treatment against systemic cryptococcosis.

Fitness and virulence costs of Candida albicans FKS1 hot spot mutations associated with echinocandin resistance

The identification of FKS1 mutations in Candida albicans associated with echinocandin resistance has raised concerns over the spread of drug-resistant strains. We studied the impact of fks1 mutations on C. albicans virulence and fitness. Compared with wild-type strains for FKS1, echinocandin-resistant C. albicans strains with homozygous fks1 hot-spot mutations had reduced maximum catalytic capacity of their glucan synthase complexes and thicker cell walls attributable to increased cell wall chitin content. The fks1 mutants with the highest chitin contents had reduced growth rates and impaired filamentation capacities. Fks1 mutants were hypovirulent in fly and mouse models of candidiasis, and this phenotype correlated with the cell wall chitin content. In addition, we observed reduced fitness of echinocandin-resistant C. albicans in competitive mixed infection models. We conclude that fks1 mutations that confer echinocandin resistance come at fitness and virulence costs, which may limit their epidemiological and clinical impact.

Recent advances in the treatment of mucormycosis

In recent years, substantial advances have been achieved in the treatment of mucormycosis. It is now clear that early initiation of therapy results in substantially better outcomes, underscoring the need to maintain a high index of suspicion and aggressively biopsy potential lesions. Increasing data support the need for surgical excision of infected and/or necrosed tissue whenever feasible. Based on their superior safety and efficacy, lipid formulations of amphotericin B have become the standard treatment for mucormycosis. Posaconazole may be useful as salvage therapy, but cannot be recommended as primary therapy for mucormycosis based on available data. Pre-clinical and limited retrospective clinical data suggest that combination therapy with lipid formulations of amphotericin and an echinocandin improves survival during mucormycosis. A definitive trial is needed to confirm these results. The use of the iron chelator, deferasirox, as adjunctive therapy also improved outcomes in animal models of mucormycosis. However, its efficacy was not confirmed in a recent, phase 2 clinical trial. Additional study is required of the potential for abrogation of iron acquisition as adjunctive treatment of mucormycosis. Combination polyene-posaconazole therapy was of no benefit in pre-clinical studies. Adjunctive therapy with recombinant cytokines, hyperbaric oxygen, and/or granulocyte transfusions can be considered in selected patients. Large-scale, prospective, randomized clinical trials are needed to define optimal management strategies for mucormycosis.

Mucormycosis: its contemporary face and management strategies

Several countries have seen rising frequencies of mucormycosis among patients with haematological disorders, malignancies, or diabetes mellitus, and among transplant recipients. Growing numbers of immunocompromised hosts, widespread use of antifungal agents inactive against mucormycosis, or other unidentified factors, could be contributing to this situation. The predominant clinical manifestations of mucormycosis vary from host to host. Additionally, risk factors specific to different subgroups have been identified, such as leukaemia, allogeneic haemopoietic stem-cell transplant, voriconazole prophylaxis, diabetes, and malnutrition. We summarise the current state of knowledge of characteristics and risk factors and discuss topical developments in therapeutic methods and strategies in the management of mucormycosis.