In vitro susceptibilities of Paracoccidioides brasiliensis yeast form to antifungal drugs In-vitro-Empfindlichkeit von Paracoccidioides brasiliensis in der Hefephase fur Antimyzetika

Lipid Systems for the Delivery of Amphotericin B in Antifungal Therapy

Amphotericin B (AmB), a broad-spectrum polyene antibiotic in the clinic for more than fifty years, remains the gold standard in the treatment of life-threatening invasive fungal infections and visceral leishmaniasis. Due to its poor water solubility and membrane permeability, AmB is conventionally formulated with deoxycholate as a micellar suspension for intravenous administration, but severe infusion-related side effects and nephrotoxicity hamper its therapeutic potential. Lipid-based formulations, such as liposomal AmB, have been developed which significantly reduce the toxic side effects of the drug. However, their high cost and the need for parenteral administration limit their widespread use. Therefore, delivery systems that can retain or even enhance antimicrobial efficacy while simultaneously reducing AmB adverse events are an active area of research. Among those, lipid systems have been extensively investigated due to the high affinity of AmB for binding lipids. The development of a safe and cost-effective oral formulation able to improve drug accessibility would be a major breakthrough, and several lipid systems for the oral delivery of AmB are currently under development. This review summarizes recent advances in lipid-based systems for targeted delivery of AmB focusing on non-parenteral nanoparticulate formulations mainly investigated over the last five years and highlighting those that are currently in clinical trials.

Clinical and epidemiological features of paracoccidioidomycosis due to Paracoccidioides lutzii

BACKGROUND

The fungus Paracoccidioides lutzii was recently included as a new causative species of paracoccidioidomycosis (PCM) and most cases have been reported from Brazil. According to available epidemiological information, P. lutzii is concentrated in the Middle-West region in Brazil, mainly in the state of Mato Grosso. However, clinical and laboratorial data available on patients infected with P. lutzii remain extremely limited.

METHODOLOGY/MAIN FINDINGS

This work describes the clinical manifestations of 34 patients suffering from PCM caused by P. lutzii, treated along 5 years (2011-2017) at a reference service center for systemic mycoses in Mato Grosso, Brazil. Adult rural workers (men), aged between 28 and 67 predominated. All patients had the chronic form of the disease, and the oral mucosa (n = 19; 55.9%), lymph nodes (n = 23; 67.7%), skin (n = 16; 47.1%) and lung (n = 28; 82.4%) were the most affected sites. Alcohol intake (n = 19; 55.9%) and smoking (n = 29; 85.3%) were frequent habits among the patients. No patient suffered from any other life-threatening disease, such as tuberculosis, cancer or other inflammatory or infectious parasitic diseases. The positivity in culture examination (97.1%) was higher than that found for the direct mycological examination (88.2%). Particularly, one patient presented fungemia at diagnosis, which lead to his death. The time elapsed between the initial symptoms and the initiation of treatment of PCM caused by P. lutzii was 19.7 (31.5) months, with most patients diagnosed 7 months after the symptoms' onset.

CONCLUSIONS/SIGNIFICANCE

Compared with the classical clinical-epidemiological profile of PCM caused by P. brasiliensis, the results of this descriptive study did not show significant clinical or epidemiological differences that could be attributed to the species P. lutzii. Future studies may confirm or refute the existence of clinical differences between the two fungal species.

Transcriptional profile of Paracoccidioides spp. in response to itraconazole

BACKGROUND

Itraconazole is currently used to treat paracoccidioidomycosis. The mechanism of action of azoles has been elucidated in some fungi, although little is known regarding its mechanism of action in Paracoccidioides spp. The present work focused on identification of regulated transcripts using representational difference analysis of Paracoccidioides spp. yeast cells treated with itraconazole for 1 and 2 h.

RESULTS

Paracoccidioides Pb01 genes up-regulated by itraconazole included genes involved in cellular transport, metabolism/energy, transcription, cell rescue, defense and virulence. ERG11, ERG6, ERG3, ERG5 and ERG25 were up-regulated at multiple time points. In vivo infection experiments in mice corroborated the in vitro results. Ergosterol levels and distribution were evaluated in Paracoccidioides Pb18 yeast cells, and the results demonstrate that both factors were changed in the fungus treated with itraconazole.

CONCLUSION

To our knowledge, this is the first transcriptional analysis of Paracoccidioides spp. exposed to a triazole drug. Here acetyl seems to be intensively produced from different metabolic pathways to produce ergosterol by the action of ergosterol synthesis related enzymes, which were also affected in other fungi. Among the genes affected, we identified genes in common with other fungi, as well as genes unique to Paracoccidioides Pb01. Those genes could be considered target to new drugs. Voltage-gated Ca2+ alpha subunit (CAV), Tetracycline resistance protein (TETA) and Hemolisyn-iii channel protein (HLYiii) were found only here and a probably involvement with resistance to itraconazole could be investigated in the future. However our findings do not permit inference to current clinical practice.

Microplate alamarBlue assay for Paracoccidioides susceptibility testing

CLSI method M27-A3 is not available for use with dimorphic fungi, such as those of the Paracoccidioides genus. In this study, we developed a microdilution method and added the alamarBlue reagent to test the responses of Paracoccidioides brasiliensis and Paracoccidioides lutzii against amphotericin B and itraconazole antifungals. The test proved to be sensitive, practical, and inexpensive and can be used to monitor the activity of low-growth microorganisms and their response to various drugs.

Influence of different media, incubation times, and temperatures for determining the MICs of seven antifungal agents against Paracoccidioides brasiliensis by microdilution

MIC assays with Paracoccidioides brasiliensis, the etiological agent of paracoccidioidomycosis, had been conducted with variable protocols, employing both macrodilution and microdilution tests and including differences in inoculum preparation, media used, incubation periods, and temperatures. Twenty-one clinical and environmental isolates of Paracoccidioides were tested using amphotericin B, itraconazole, ketoconazole, fluconazole, sulfamethoxazole, sulfamethoxazole-trimethoprim, and terbinafine, according to the National Committee for Clinical Laboratory Standards (National Committee for Clinical Laboratory Standards, document M27-A2, 2002), with modifications such as three medium formulations (RPMI 1640 medium, McVeigh and Morton [MVM] medium, and modified Mueller-Hinton [MMH] medium), two incubation temperatures (room temperature [25 to 28 °C] and 37 °C), and three incubation periods (7, 10, and 15 days). The antifungal activities were also classified as fungicidal or fungistatic. The best results were obtained after 15 days of incubation, which was chosen as the standard incubation time. The MICs for most individual isolates grown for the same length of time at the same temperature varied with the different media used (P < 0.05). Of the isolates, 81% showed transition from the yeast to the mycelial form in RPMI 1640 medium at 37 °C, independent of the presence of antifungals. MMH medium appears to be a suitable medium for susceptibility testing of antifungal drugs with P. brasiliensis, except for sulfamethoxazole and the combination of sulfamethoxazole-trimethoprim, for which the MVM medium yielded better results. The incubation temperature influenced the MICs, with, in general, higher MICs at 25 °C (mycelial form) than at 37 °C (P < 0.05). Based on our results, we tentatively propose a microdilution assay protocol for susceptibility testing of antifungal drugs against Paracoccidioides.

The effect of Leptospermum petersonii essential oil on Candida albicans and Aspergillus fumigatus

A variety of assays were utilized to determine the effects of Leptospermum petersonii essential oil on both Candida albicans and Aspergillus fumigatus. Hyphal morphology, susceptibility of spheroplasts and uptake of propidium iodide following exposure to the oil suggest that the mode of action of L. petersonii essential oil is through direct disturbance of the fungal cell membrane. Data also confirms that the volatile component of the oil is highly antifungal, independent of direct contact between the liquid oil and the fungal membrane. The degree of inhibition was greater when fungi were directly exposed to oil volatiles compared to pre-inoculation exposure of oil volatiles into the agar. It is likely that the essential oil volatiles are acting both directly and indirectly on the fungi to produce growth inhibition.

Cyclosporin A treatment and decreased fungal load/antigenemia in experimental murine paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the fungus Paracoccidioides brasiliensis (Pb). The cyclosporin A (CsA) is an immunosuppressant drug that inhibits calcineurin and has been described as a potential antifungal drug. The present study investigated the effect of CsA on the immune response, fungal load/antigenemia in experimental murine PCM. It was used four groups of BALB/c mice: (a) infected with 1 x 10⁵ Pb18 yeast cells (Pb), (b) infected and treated with CsA every other day 10 mg/kg of CsA (s.c.) during 30 days (Pb/CsA), (c) treated with CsA (CsA) and (d) no infected/treated (PBS). The immune response was evaluated by lymphocyte proliferation, DTH assays to exoAgs, ELISA for IgG anti-gp43 (specific immune responses) and cytokine serum levels (IFN-γ, TNF-α, IL-4 and IL-10). Fungal load was determined by lung colony-forming units (CFU) counts, lung and liver histopathology analysis and antigenemia determined by inhibition-ELISA. As expected, CsA was able to inhibit the specific cellular and humoral immune response (P < 0.05), with decrease in serum IFN-γ, TNF-α and IL-4 levels (P < 0.05). Cyclosporin A treatment also resulted in significantly decreased lung Pb CFU (P < 0.05) as well as a lower number of yeasts in the lung and liver (P < 0.05) by histopathology. In concordance, the decreased antigenemia was observed in Pb/CsA group (P < 0.05). In conclusion, even with immunosuppressive action, treatment with CsA results in decreased lung fungal load/antigenemia in experimental PCM in BALB/c mice. Further study is required to determine whether this represents less severe disease or protection by CsA.

Determination of susceptibility/resistance to antifungal drugs of Trichophyton mentagrophytes isolates by a macrodilution method

Onychomycosis is a common adult human mycosis, and dermatophytes of the Trichophyton genera are the most frequently isolated microorganism. Globally, from 3% to 10% of the human population is attacked by ony cho mycosis, and many cases involve toenails. The aim of this work was to determine the minimal inhibitory concentrations (MICs) of antifungal drugs (fluconazole, ketoconazole, itraconazole, terbinafine, and griseofulvin) often used for the treatment of ungueal dermatophytosis caused by Trichophyton mentagrophytes. The MICs were determined by the broth medium macrodilution method. The results showed that activities of terbinafine and itraconazole were significantly higher (MIC <0.007-0.015 microg.mL -1 and MIC = 0.062-1.000 microg.mL -1, respectively). All isolates had reduced susceptibility to fluconazole (MIC = 16 to >64 microg.mL -1). The MICs of ketoconazole and griseofulvin varied among strains, ranging from 0.125 to 2.000 microg.mL -1 for ketoconazole and from 0.25 to 2.00 microg.mL -1 for griseofulvin. These MICs were higher than those of other studies cited, possibly because of differences in culture medium used in the other studies.

Tropical dermatology: fungal tropical diseases

Fungal infections are common in tropical countries and can have an important impact on public health. Lobomycosis is a common fungal infection in the tropical rain forest of South America, and paracoccidioidomycosis (South American blastomycosis) is a widespread and sometimes severe illness. Penicilliosis marneffei is an opportunistic infection of AIDS patients in southeast Asia. Chromoblastomycosis and mycetomas are causes of morbidity around the world. Sporotrichosis is a worldwide subcutaneous mycosis with a high incidence in tropical countries and is an important illness in immunocompromised patients. Rhinosporidiosis was classed as a fungal infection but is now considered a protistan parasite that belongs to the class Mesomycetozoea. It is included in this review because of its historical classification. In the past, most of these mycoses were restricted to specific geographic areas and natural reservoirs. There are, however, situations in which people from other regions come in contact with the pathogen. A common situation involves an accidental contamination of a traveler or worker who has contact with a tropical mycosis. Even minor trauma to the skin surface or inhalation of the fungal conidia can infect the patient. Thus recognition of the clinical symptoms and the dermatologic findings of the diseases, as well as the geographic distribution of the pathogens, can be critical in diagnosis of the tropical mycoses. This review discusses some of the more common tropical subcutaneous and systemic mycoses, as well as their signs, symptoms, methods of diagnosis, and therapies.

LEARNING OBJECTIVE

At the completion of this learning activity, participants should be able to recognize the clinical and histologic presentations of tropical fungal diseases with cutaneous manifestations and be familiar with the appropriate therapies.

Randomly amplified polymorphic DNA as a valuable tool for epidemiological studies of Paracoccidioides brasiliensis

Randomly amplified polymorphic DNA (RAPD) has been successfully used to detect genetic variations among isolates of Paracoccidioides brasiliensis. However, the usefulness of this technique for assessing important parasitic properties is still unconfirmed. In the present work we further investigated the applicability of RAPD in revealing important intrinsic and extrinsic features of this fungus associated with geographical origin, time of isolation, source of clinical specimen, clinical forms of human disease and also in vitro and in vivo susceptibility to antimicrobial and antifungal drugs. The RAPD patterns allowed us to distinguish all of the analyzed strains, which included 26 clinical isolates, 2 animal isolates, and 1 environmental isolate of P. brasiliensis obtained from different geographic regions, confirming the strong discriminating power of this technique. A phenetic tree, build from the RAPD data, showed that although the two nonclinical Brazilian strains were set together the majority of the clinical Brazilian strains were randomly distributed through different sub-branches of a major cluster without any correlation to any of the parameters analyzed. A second major cluster, however, has grouped isolates from Mato Grosso and Roraima (Brazil) that not only were susceptible in vitro to trimethoprim-sulfamethoxazole but also produced a good in vivo response. These results open new vistas for epidemiological and clinical studies of P. brasiliensis.

In vitro comparison of activities of terbinafine and itraconazole against Paracoccidioides brasiliensis

In vitro, terbinafine is highly active against a broad spectrum of pathogenic fungi. We evaluated the activities of terbinafine and itraconazole against 31 isolates of Paracoccidioides brasiliensis. The tests were conducted by using a broth macrodilution procedure. MICs, in micrograms per milliliter, were as follows: terbinafine, 0.015 to 1.0 (geometric mean, 0.1188); itraconazole, 0.007 to 0.5 (geometric mean, 0.03165). The usual therapy for paracoccidioidomycosis is sulfonamides, amphotericin B, and azole derivatives (ketoconazole, itraconazole, and fluconazole). In comparison to amphotericin B, azole derivatives allow shorter treatment courses, can be administered orally, and are equally effective. Itraconazole has as high efficacy as ketoconazole, but with superior tolerance. It is the current drug of choice for treatment of paracoccidioidomycosis. The data obtained in this study indicate that terbinafine is active against P. brasiliensis in vitro and suggest that this allylamine can be considered a new option as drug therapy for paracoccidioidomycosis.

Antifungal use in HIV infection

Systemic fungal infections continue to be a major cause of morbidity and mortality among HIV-infected patients. Mucosal candidiasis remains the most common fungal disease in this population, while cryptococcosis and aspergillosis are associated with significant mortality. Histoplasmosis and penicilliosis are relatively common in some areas. Blastomycosis, coccidioidomycosis and paracoccidioidomycosis have also been described in association with HIV. Over the last decade, a number of clinical trials have evaluated the use of antifungal therapies in this population and shaped our approach to prophylaxis and therapy. This report outlines the state of the art in the management of HIV-associated fungal infections and discusses the unique difficulties and drug-drug interactions associated with managing fungal infections in this population. Deoxycholate or liposomal formulations of amphotericin B and the triazoles fluconazole and itraconazole are the most commonly used antifungal agents. Healthcare providers should be familiar with the appropriate antifungal management and its limitations. Possible interactions with antiretrovirals should be considered when prescribing antifungal treatment. An exciting new decade in antifungal therapy is beginning, in which the second-generation triazoles and echinocandins will hopefully help us to overcome the limitations of the current antifungal arsenal.