Recent developments in the diagnosis and treatment of subcutaneous mycoses

Human Fungal Pathogens of Mucorales and Entomophthorales

In recent years, we have seen an increase in the number of immunocompromised cohorts as a result of infections and/or medical conditions, which has resulted in an increased incidence of fungal infections. Although rare, the incidence of infections caused by fungi belonging to basal fungal lineages is also continuously increasing. Basal fungal lineages diverged at an early point during the evolution of the fungal lineage, in which, in a simplified four-phylum fungal kingdom, Zygomycota and Chytridiomycota belong to the basal fungi, distinguishing them from Ascomycota and Basidiomycota. Currently there are no known human infections caused by fungi in Chytridiomycota; only Zygomycotan fungi are known to infect humans. Hence, infections caused by zygomycetes have been called zygomycosis, and the term "zygomycosis" is often used as a synonym for "mucormycosis." In the four-phylum fungal kingdom system, Zygomycota is classified mainly based on morphology, including the ability to form coenocytic (aseptated) hyphae and zygospores (sexual spores). In the Zygomycota, there are 10 known orders, two of which, the Mucorales and Entomophthorales, contain species that can infect humans, and the infection has historically been known as zygomycosis. However, recent multilocus sequence typing analyses (the fungal tree of life [AFTOL] project) revealed that the Zygomycota forms not a monophyletic clade but instead a polyphyletic clade, whereas Ascomycota and Basidiomycota are monophyletic. Thus, the term "zygomycosis" needed to be further specified, resulting in the terms "mucormycosis" and "entomophthoramycosis." This review covers these two different types of fungal infections.

Chromoblastomycosis

Chromoblastomycosis is a chronic subcutaneous mycotic infection caused by pigmented or dematiaceous saprophytic moulds ubiquitous in the environment. The most common etiologic agents are Fonsecaea pedrosoi and Cladophialophora carrionii, both of which can be isolated from plant debris. The infection usually follows traumatic inoculation through penetrating thorn or splinter wounds. The fungal agents develop as small clusters of cells known as muriform bodies. Several months after the injury, painless papules or nodules appear in the affected area progressing to scaly and verrucose plaques. Direct examinations of skin scrapings or histopathologic study demonstrates the typical muriform bodies. Microbiologic culture is necessary for the correct determination of the etiologic agent. Itraconazole is the treatment of choice, often in combination with surgery. Even so, results are often unsatisfactory as patients present late to medical services because of lack of funds and the fact that the disease usually affects the main family earner.

[Importance of the sporotrichosis asteroid body for the rapid diagnosis of sporotrichosis]

Eighty patients with cutaneous sporotrichosis were studied between 1985 and 1996. The investigation of asteroid bodies (AB) was done by direct microscopic slides examination of pus obtained from the lesions. Patients were divided into two groups: 32 consulting before 1989, and 48 consulting after 1990. In the first group, material was obtained as usual by simple digital pressure of the most productive lesion, and then wet preparation microscopic examination was performed. Fourteen patients with AB were found in this group (43.75%). In the second group the initial pus was discarded and new samples were taken more deeply, and examined up to five slides for each patient. The slides were carefully examined at light microscope. Fourty five patients with AB were detected in this group (93.75%). All eighty samples were cultured and all of them were positive for Sporothrix schenckii. The change of methodology to obtain the samples and the exhaustive observations, increased the possibility of AB detection. ABs are of great diagnostic value and might be of importance to initiate treatment before reporting culture.

Susceptibility of sequential Fonsecaea pedrosoi isolates from chromoblastomycosis patients to antifungal agents. Antimykotika-Empfindlichkeit von sequenziellen Fonsecaea pedrosoi-Isolaten von Chromoblastomykose-Patienten

Fourteen Fonsecaea pedrosoi isolates from six chromoblastomycosis patients were submitted to susceptibility testing. Some patients were undergoing treatment with itraconazole (ITZ) and/or cryosurgery with liquid nitrogen. The antifungal agents amphotericin B (AMB), ITZ, fluconazole (FCZ), ketoconazole (KCZ), 5-fluorocytosine (5-FC), and terbinafine (TBF) were tested. AMB and FCZ showed less activity for all isolates. The most active agents were KCZ and TBF. Sequentially isolates from four patients presented ITZ minimal inhibitory concentration (MIC) higher than the previous ones; for two of these patients, response to therapy with this agent was not observed. These results suggest development of microbiologic resistance to ITZ in four instances, two of them coinciding with lack of clinical response to this drug.

In vitro susceptibility of chromoblastomycosis and phaeohyphomycosis agents to antifungal drugs

The in vitro susceptibility of chromoblastomycosis and phaeohyphomycosis agents to antifungal drugs was appraised using the reference macrodilution method proposed by the National Committee for Clinical Laboratory Standards (NCCLS) for yeasts modified for filamentous fungi. The antifungal drugs amphotericin B, 5-fluorocytosine, itraconazole and fluconazole were tested against one environmental and 18 clinical isolates. This work amended the macrodilution methods proposed by NCCLS and suggests that a conidial suspension free of hyphae leads to a more reliable assay and provides for better reproducibility. The macrodilution method was performed with 10(4) conidia ml-1. The MIC values ranged from 1.0 to 16.0 micrograms ml-1 for amphotericin B and 3.12 to 25.0 micrograms ml-1 for 5-fluorocytosine. A MIC range of 0.06 to 1.95 micrograms ml-1 was determined for itraconazole while 2.0 to 64.0 micrograms ml-1 was detected for fluconazole.

A review of zygomycosis due to Basidiobolus ranarum

Zygomycosis due to Basidiobolus ranarum (entomophthoromycosis basidiobolae, subcutaneous zygomycosis, subcutaneous phycomycosis, basidiobolomycosis) is a granulomatous infection of the skin and subcutaneous tissues characterized by the formation of fluctuant firm and non-tender swellings, generally on the extremities, trunk and rarely other parts of the body. The causative agent is common in soil, decaying vegetable matter, and the gastrointestinal tracts of amphibians, reptiles, fish and bats. It is presumed that infection is acquired through exposure to B. ranarum following minor trauma to skin or insect bites. The disease usually occurs in children, less often in adolescents and rarely in adults. Males are much more frequently affected than females. Laboratory diagnosis is based on histopathology and culture. The typical histopathological feature is the presence of thin-walled, broad often aseptate hyphae or hyphal fragments with an eosinophilic sheath, frequently phagocytized within giant cells. Basidiobolus ranarum is known to produce several enzymes, e.g. lipase and protease that probably play roles in the pathogenesis of infections caused by this mould. An immunological test has been developed for specific diagnosis of the disease. Though potassium iodide (KI) has been the traditional drug employed in the treatment of infections by B. ranarum, several other drugs, viz amphotericin B, cotrimoxazole, ketoconazole, itraconazole and fluconazole have been successfully tried.

Nasal rhinosporidiosis in dogs: four cases from Europe and a review of the literature

This paper describes four cases of canine rhinosporidiosis which occurred in Italy in 1994 and 1995. Four dogs with a history of exposure to the muddy environment of rice fields, developed respiratory signs. Rhinoscopy revealed nasal polypoid lesions with a characteristic gross appearance due to the presence of multiple, tiny, white-yellowish spots representing sporangia filled with spores. In cytological samples obtained by brushing, many spores were present in an inflammatory background. Histologically, the polyps consisted of fibrovascular tissue embedding sporangia in different developmental stages, and free spores which elicited a severe pyogranulomatous inflammation. All the dogs were treated surgically and the condition did not recur in two cases during a year's follow-up and in the other two cases during two years.

Treatment of chromomycosis with terbinafine: preliminary results of an open pilot study

In an open trial, long courses (6-12 months) of terbinafine at a dosage of 500 mg/day were administered orally to 43 patients with a diagnosis of chromomycosis. Sixteen patients (37.2%) had previously relapsed after one or two courses of thiabendazole. A spectacular improvement in the lesions, including disappearance of bacterial superinfections and of associated oedema and elephantiasis, was observed as soon as 2-4 months after the beginning of treatment. The mean number of fungal cells in skin scrapings fell by about 70% in 4 months. Mycological cure, as judged by skin scrapings, was observed in 41.4, 74.1 and 82.5% of patients infected with Fonsecaea pedrosoi after 4, 8 and 12 months of therapy, respectively. For the first time with this disease, total cure was observed even in imidazole-refractory patients or chronic cases (47.2% with a lesion present for longer than 10 years). The efficacy of terbinafine in Cladosporium carrionii-infected patients seemed higher, as indicated by the examination at 4 months.