In vitro antifungal susceptibility of Cladophialophora carrionii, an agent of human chromoblastomycosis

Galleria mellonella in vitro model for chromoblastomycosis shows large differences in virulence between isolates

BACKGROUND

Chromoblastomycosis is the World Health Organization (WHO)-recognized fungal implantation disease that eventually leads to severe mutilation. Cladophialophora carrionii (C. carrionii) is one of the agents. However, the pathogenesis of C. carrionii is not fully investigated yet.

METHODS

We investigated the pathogenic potential of the fungus in a Galleria mellonella (G. mellonella) larvae infection model. Six strains of C. carrionii, and three of its environmental relative C. yegresii were tested. The G. mellonella model was also applied to determine antifungal efficacy of amphotericin B, itraconazole, voriconazole, posaconazole, and terbinafine.

RESULTS

All strains were able to infect the larvae, but virulence potentials were strain-specific and showed no correlation with clinical background of the respective isolate. Survival of larvae also varied with infection dose, and with growth speed and melanization of the fungus. Posaconazole and voriconazole exhibited best activity against Cladophialophora, followed by itraconazole and terbinafine, while limited efficacy was seen for amphotericin B.

CONCLUSION

Infection behavior deviates significantly between strains. In vitro antifungal susceptibility of tested strains only partly explained the limited treatment efficacy in vivo.

Cladosporium halotolerans: Exploring an Unheeded Human Pathogen

BACKGROUND

Cladosporium halotolerans is a saprobic fungus, rarely implicated in human infections. The identification is challenging due to non-specific phenotypic features.

OBJECTIVE

To decipher clinical spectrum, microbiological and susceptibility profile of clinical and environmental isolates of Cladosporium halotolerans.

METHOD

All the isolates identified as Cladosporium halotolerans deposited in National Culture Collection for Pathogenic Fungi (NCCPF), Postgraduate Institute of Medical Education and Research, Chandigarh, India were revived. Phenotypic and molecular characterization targeting internal transcribed spacer (ITS) region of ribosomal DNA, large subunit of ribosomal DNA (LSU; NL1 and NL4), actin (ACT) and beta-tubulin (TUB) was done. Scanning electron microscopy (SEM) was performed to determine any phenotypic variations. Antifungal susceptibility testing (AFST) was carried out for eight antifungal agents as per CLSI M38 Ed3 guidelines. We also performed systematic literature review of all the cases of Cladosporium halotolerans reported till date.

RESULTS

A total of four isolates (clinical, n = 3; soil, n = 1) identified as Cladosporium halotolerans were included in the study. The clinical sites were skin, maxillary tissue and nail. All patients were apparently immunocompetent, and history of trauma was recorded in one patient. All patients improved on antifungal therapy. The cultures revealed growth of black mycelial fungus and microscopic examination demonstrated dematiaceous septate hyphae with erect conidiophores and conidia in branched acropetal chains. Based on molecular methods, all the four isolates were identified as C. halotolerans. SEM revealed no variation in length and width of the conidia, conidiophores, ramoconidium and hyphae among the isolates. All molecular targets, such as ITS region, LSU (partially sequenced), ACT and TUB were able to differentiate the isolates. Minimum inhibitory concentrations for antifungals were: triazoles (0.12-2 μg/ml), amphotericin B (4 μg/ml) and echinocandins (2-8 μg/ml).

CONCLUSION

We report role of the rarely isolated dematiaceous fungus, C. halotolerans, in causing human infections. The study emphasizes the role of molecular methods in precisely identifying these species. Triazoles are more active against these black fungi compared to polyenes or echinocandins.

The origin of human pathogenicity and biological interactions in Chaetothyriales

Fungi in the order Chaetothyriales are renowned for their ability to cause human infections. Nevertheless, they are not regarded as primary pathogens, but rather as opportunists with a natural habitat in the environment. Extremotolerance is a major trend in the order, but quite different from black yeasts in Capnodiales which focus on endurance, an important additional parameter is advancing toxin management. In the ancestral ecology of rock colonization, the association with metabolite-producing lichens is significant. Ant-association, dealing with pheromones and repellents, is another mainstay in the order. The phylogenetically derived family, Herpotrichiellaceae, shows dual ecology in monoaromatic hydrocarbon assimilation and the ability to cause disease in humans and cold-blooded vertebrates. In this study, data on ecology, phylogeny, and genomics were collected and analyzed in order to support this hypothesis on the evolutionary route of the species of Chaetothyriales. Comparing the ribosomal tree with that of enzymes involved in toluene degradation, a significant expansion of cytochromes is observed and the toluene catabolism is found to be complete in some of the Herpotrichiellaceae. This might enhance human systemic infection. However, since most species have to be traumatically inoculated in order to cause disease, their invasive potential is categorized as opportunism. Only in chromoblastomycosis, true pathogenicity might be surmised. The criterion would be the possible escape of agents of vertebrate disease from the host, enabling dispersal of adapted genotypes to subsequent generations.

In vitro activities of 8 antifungal drugs against 126 clinical and environmental Exophiala isolates

BACKGROUND

Exophiala is the main genus of black fungi comprising numerous opportunistic species. Data on antifungal susceptibility of Exophiala isolates are limited, while infections are potentially fatal.

MATERIALS AND METHODS

In vitro activities of eight antifungal drugs (AMB, five azoles, two echinocandins) against 126 clinical (n = 76) and environmental (n = 47) isolates from around the world were investigated. E. oligosperma (n = 58), E. spinifera (n = 33), E. jeanselmei (n = 14) and E. xenobiotica (n = 21) were included in our dataset.

RESULTS

The resulting MIC₉₀ s of all strains were as follows, in increasing order: posaconazole 0.063 μg/ml, itraconazole 0.125 μg/ml, voriconazole and amphotericin B 1 μg/ml, isavuconazole 2 μg/ml, micafungin and caspofungin 4 μg/ml, and fluconazole 64 μg/ml. Posaconazole, itraconazole and micafungin were the drugs with the best overall activity against Exophiala species. Fluconazole could not be considered as a treatment choice. No significant difference could be found among antifungal drug activities between these four species, neither in clinical nor in environmental isolates.

CONCLUSION

Antifungal susceptibility data for Exophiala spp. are crucial to improve the management of this occasionally fatal infection and the outcome of its treatment.

In vitro activities of nine antifungal agents against rare pathogenic fungi

Purpose. To assess in vitro activities of nine antifungal agents (amphotericin B, fluconazole, voriconazole, itraconazole, posaconazole, caspofungin, micafungin, terbinafine and 5-flucytosine) against 93 strains of rare pathogenic fungi and the combined effects of drug combinations against several multidrug-resistant fungi.Methodology. The broth microdilution method M38-A3 and M27-A4 from the Clinical and Laboratory Standards Institute and the checkerboard method were performed in this study.Results. Low MICs for fluconazole were observed in moulds including Tritirachium oryzae, Exophiala attenuata and yeasts. MICs for amphotericin B>2 µg ml^-1 were found among Aspergillus nidulans, Fusarium napiforme, Trichoderma longibrachiatum, Tritirachium oryzae, Cunninghamella bertholletiae, Cunninghamella phaeospora, Conidiobolus coronatus, Exophiala attenuata, Ochroconis mirabilis and Rhinocladiella basitona. Multidrug resistance was observed in Microascus spp., Lomentospora prolificans and Pythium insidiosum.Conclusion. Our study illustrated in vitro drug susceptibilities of some rare pathogenic fungi, which provide data to guide clinical treatment of fungal infections.

Isavuconazole for treatment of rare invasive fungal diseases

Data regarding treatment of rare invasive fungal diseases (IFDs) are scarce. We documented the efficacy and safety of isavuconazole for treatment of uncommonly diagnosed IFDs. VITAL was a single-arm, international, open-label study evaluating the efficacy and safety of isavuconazole (200 mg orally or intravenously every 8 hours for 48 hours, then once daily). The primary outcome was overall response at Day 42; key secondary outcomes were overall responses at Day 84 and end of treatment (EOT), mortality at Days 42 and 84, and safety. This analysis includes patients with IFD caused by rare or unidentified pathogens. Twenty-six patients with IFDs caused by rare moulds (n = 17), non-Candida yeasts (n = 2), or unidentified moulds (n = 7) were enrolled (median treatment duration [range], 114.5 [1-496]) days. Overall treatment success was observed in 11/26 (42.3%), 10/26 (38.5%), and 15/26 (57.7%) patients at Days 42, 84, and EOT, respectively. All-cause mortality rates were 2/26 patients (7.7%) at Day 42 and 4/26 patients (15.4%) at Day 84; another two patients died after Day 84. All patients had ≥1 treatment-emergent adverse event (TEAE); 15 patients (57.7%) had serious TEAEs, and TEAEs led to discontinuation of isavuconazole in four patients (15.4%). Isavuconazole may be efficacious for treatment of a range of rare IFDs.

In vitro susceptibility of chromoblastomycosis agents to antifungal drugs: A systematic review

Chromoblastomycosis (CBM) is a chronic granulomatous mycosis caused by dematiaceous fungi that affects cutaneous and subcutaneous tissues. The standard antifungal drug for treatment is itraconazole, followed by terbinafine. However, cure rates vary from 15% to 80% when these drugs are used as monotherapy. A systematic review of the in vitro susceptibility of CBM agents to antifungal drugs, alone and in combination, was conducted using the Cochrane methodology. Forty-seven search terms were included in the PICOS method of searching electronic databases. The search resulted in 35 studies, of which 8 evaluated antifungal drugs in combination. Based on minimum inhibitory concentrations (MICs), posaconazole, terbinafine, itraconazole and voriconazole were, in descending order, the most effective antifungal drugs against CBM agents in vitro. In drug combination studies, only terbinafine-voriconazole and itraconazole-caspofungin showed 100% synergy for Fonsecaea pedrosoi, Exophiala jeanselmei and Phialophora verrucosa. However, none of the combinations studied showed antagonism.

Novel treatment using topical malachite green for nasal phaeohyphomycosis caused by a new Cladophialophora species in a cat

CASE SUMMARY

A 1.5-year-old castrated male domestic shorthair cat presented with a 2 month history of progressive nasal swelling and hyporexia. Minimal improvement prior to referral was achieved with a course of antibiotics and glucocorticoids. Cytology of an ulcerative lesion on the dorsal aspect of the nose was consistent with a diagnosis of phaeohyphomycosis. The cat achieved static disease for 6 weeks following initiation of itraconazole but developed epistaxis at 9 weeks. CT of the head demonstrated nasal and frontal sinus involvement. Nasal biopsy and culture identified infection with a Cladophialophora species not previously reported to cause disease. Initial response to a combination of itraconazole and terbinafine was noted, but owing to severe thrombocytopenia this combination was discontinued. Voriconazole was used but discontinued because of adverse side effects. Posaconazole treatment was offered throughout the clinical course but rejected owing to financial constraints and an uncertain response to medical therapy. Rhinotomy with debulking of diseased tissue and topical malachite green treatment was performed. Following the procedure itraconazole was continued and the cat has had no recurrence for over 1 year.

RELEVANCE AND NOVEL INFORMATION

Infections by Cladophialophora species have been reported in veterinary species, including cats. The specific fungal organism isolated from this cat has not been previously reported to cause disease in humans or animals and has only been described in the mangroves of Brazil. Furthermore, this is the first report to describe the use of topical malachite green as a treatment for refractory phaeohyphomycosis.

Successful treatment of chromoblastomycosis of 10-year duration due to Fonsecaea nubica

We report a case of chromoblastomycosis due to the presence of large plaque and verrucous hyperplasia lesions on the left upper limb, with elbow abnormal activities, in a 56-year-old male. The diagnosis of chromoblastomycosis was based on gross and microscopic morphologies, histopathological examination and clinical manifestation. Molecular tools were applied to identifying the causative agent Fonsecaea nubica, which is rarely reported to be associated with chromoblastomycosis. The patient was initially treated orally with terbinafine (250 mg/day) and itraconazole (200 mg/day), subsequently patient received thermotherapy (45-50°C, 3 h/day) for 1 month. The patient was successfully cured. A literature review was performed to assess general features, treatment and outcome of chromoblastomycosis due to F.  nubica. All the 5 reviewed patients were male, over 30 years old and their lesions occurred after traumatic inoculation.

In Vitro Activities of Luliconazole, Lanoconazole, and Efinaconazole Compared with Those of Five Antifungal Drugs against Melanized Fungi and Relatives

The in vitro activities of novel azoles compared to those of five antifungal drugs against clinical (n = 28) and environmental (n = 102) isolates of black mold and melanized yeast were determined. Luliconazole and lanoconazole had the lowest geometric mean MICs, followed by efinaconazole, against tested isolates compared to the other drugs. Therefore, it appears that these new imidazole and triazole drugs are promising candidates for the treatment of infections due to melanized fungi and their relatives.

Chromoblastomycosis

Chromoblastomycosis (CBM), also known as chromomycosis, is one of the most prevalent implantation fungal infections, being the most common of the gamut of mycoses caused by melanized or brown-pigmented fungi. CBM is mainly a tropical or subtropical disease that may affect individuals with certain risk factors around the world. The following characteristics are associated with this disease: (i) traumatic inoculation by implantation from an environmental source, leading to an initial cutaneous lesion at the inoculation site; (ii) chronic and progressive cutaneous and subcutaneous tissular involvement associated with fibrotic and granulomatous reactions associated with microabscesses and often with tissue proliferation; (iii) a nonprotective T helper type 2 (Th2) immune response with ineffective humoral involvement; and (iv) the presence of muriform (sclerotic) cells embedded in the affected tissue. CBM lesions are clinically polymorphic and are commonly misdiagnosed as various other infectious and noninfectious diseases. In its more severe clinical forms, CBM may cause an incapacity for labor due to fibrotic sequelae and also due to a series of clinical complications, and if not recognized at an early stage, this disease can be refractory to antifungal therapy.

Dematiaceous Molds

Dematiaceous fungi are the cause of phaeohyphomycosis, a term that encompasses many clinical syndromes, from local infections due to trauma to widely disseminated infection in immunocompromised patients. These fungi are unique owing to the presence of melanin in their cell walls, which imparts the characteristic dark color to their spores and hyphae. Melanin may also be a virulence factor. Local infection may be cured with excision alone, whereas systemic disease is often refractory to therapy. Azoles have the most consistent in vitro activity. Further studies are needed to better understand the pathogenesis and treatment of these uncommon infections.

Isavuconazole, a broad-spectrum triazole for the treatment of systemic fungal diseases

The prodrug isavuconazonium sulfate (BAL8557) is an extended-spectrum water-soluble triazole, developed for the treatment of severe invasive and life-threatening fungal diseases. Its active moiety, BAL4815, is a potent inhibitor of ergosterol biosynthesis, resulting in the disruption of fungal membrane structure and function. The active compound shows broad-spectrum of activity and potency against all major opportunistic fungi, such as Aspergillus spp., Candida spp., Cryptococcus spp., Mucorales, Black yeasts and their filamentous relatives and the true pathogenic fungi, including Histoplasma capsulatum and Blastomyces dermatitidis. It is currently in Phase III clinical development for treatment of aspergillosis, candidiasis and mucormycosis, as well as other rare fungi infections. We reviewed the pharmacokinetic and pharmacodynamic characteristics of isavuconazole, and its microbiological and clinical investigation progress in advanced stages of development.

Systematic review of severe acute liver injury caused by terbinafine

BACKGROUND

Terbinafine is an effective antimicrobial agent against dermatophytes, cryptococcus and other fungi. It is the preferred drug to treat onychomycosis. However, severe acute hepatitis from oral terbinafine administration has been recently reported.

AIM

To describe a representative case, and review the literature regarding the best evidence on treatment and prognosis of severe acute hepatitis caused by oral terbinafine.

METHODS

The literature was searched for publications on severe hepatitis caused by terbinafine using MEDLINE, China Biology Medicine Disc, and the VIP Medical Information Resource System. Related references were searched manually.

RESULTS

Seventeen English and three Chinese references of case reports were included after eliminating duplicate publications. No randomized control studies were found. Liver enzyme levels were found to have been increased significantly. Abdominal ultrasound demonstrated cholestasis.

CONCLUSIONS

Severe acute liver injury is a known, but unusual complication of terbinafine exposure. The prognosis is often good with appropriate treatment. Liver function assessment before treatment and periodic monitoring 4-6 weeks after initiation of treatment is recommended.

In vitro activities of eight antifungal drugs against 106 waterborne and cutaneous exophiala species

The in vitro activities of eight antifungal drugs against 106 clinical and environmental isolates of waterborne and cutaneous Exophiala species were tested. The MICs and minimum effective concentrations for 90% of the strains tested (n = 106) were, in increasing order, as follows: posaconazole, 0.063 μg/ml; itraconazole, 0.25 μg/ml; micafungin, 1 μg/ml; voriconazole, 2 μg/ml; isavuconazole, 4 μg/ml; caspofungin, 8 μg/ml; amphotericin B, 16 μg/ml; fluconazole, 64 μg/ml.

Detection and identification of opportunistic Exophiala species using the rolling circle amplification of ribosomal internal transcribed spacers

Deep infections by melanized fungi deserve special attention because of a potentially fatal, cerebral or disseminated course of disease in otherwise healthy patients. Timely diagnostics are a major problem with these infections. Rolling circle amplification (RCA) is a sensitive, specific and reproducible isothermal DNA amplification technique for rapid molecular identification of microorganisms. RCA-based diagnostics are characterized by good reproducibility, with few amplification errors compared to PCR. The method is applied here to species of Exophiala known to cause systemic infections in humans. The ITS rDNA region of five Exophiala species (E. dermatitidis, E. oligosperma, E. spinifera, E. xenobiotica, and E. jeanselmei) was sequenced and aligned in view of designing specific padlock probes to be used for the detection of single nucleotide polymorphisms (SNPs) of the Exophiala species concerned. The assay proved to successfully amplify DNA of the target fungi at the level of species; while no cross-reactivity was observed. Amplification products were visualized on 1% agarose gels to verify the specificity of probe-template binding. Amounts of reagents were minimized to avoid the generation of false positive results. The sensitivity of RCA may help to improve early diagnostics of these difficult to diagnose infections.