Deep or systemic mycoses can be subdivided into

• Cosmopolitan deep mycoses, such as aspergillosis, candidosis and cryptococcosis. They are caused by fungi that occur worldwide.
• Exotic deep mycoses, including coccidioidomycosis and histoplasmosis and infection with Penicillium marneffei, the pathogens of which have a limited geographical distribution.

The genus Aspergillus is recognised by its typical asexual sporulation. The very numerous spores occur in chains from bottle-shaped elements (phialides) which are grouped on the swollen endings of erect hyphae. Of the approximately 180 known species, 5-6 are pathogenic, of which A. fumigatus and A. flavus occur the most frequently. Aspergillus are widespread moulds, but their growth is generally on the substrate and physical factors. Consequently, A. fumigatus, a thermotolerant species (optimum about 43°C), is extensively present in compost (it is not unusual to isolate 300,000 CFUs/g from leaf mould). In this way these moulds are sources of allergy or infection for some patients, but the previously described epidemics of fatal aspergillosis in hospital were all caused by demolition and construction work!

This colonisation (!) is characterised by the development of a free and mobile fungal mass, the fungal ball, in a residual lung cavity (80% post-tuberculosis). This mass consists of interwoven hyphae. The most typical symptom is haemoptysis, which can sometimes be profuse.

With or without other deep foci, this is usually a fatal opportunistic infection in certain risk groups such as patients with neutropenia. In the same patients extrapulmonary dispersion appears to be more frequent. Pulmonary aspergillosis is also found in AIDS patients. Not all patients with invasive pulmonary aspergillosis have immune disorders.

In non-invasive sinusitis, azoles or polyenes can be used for rinsing. Co-administration of itraconazole is recommended in the event of predisposing factors or in the case of invasive sinusitis. The severity of haemoptysis in aspergilloma will determine whether or not to operate. According to some authors, embolisation of the arteries that arise to vascularise the colonised cavity yields favourable results. Alternatives are intracavitary instillations of itraconazole or oral treatment with itraconazole.

In all forms of invasive aspergillosis, intervention should be as rapid and effective as possible. Treatment consists of IV amphotericin B, or oral itraconazole for the less serious cases.

• Amphotericin B: 0.8-1.5 mg/kg/day for at least 2 weeks
• Itraconazole: 600-800 mg/day for 3-4 days, then 400 mg/day for a few (1-26) months.
• Echinocandin

Complete prevention of aerogenic contact with Aspergillus is utopian. That does not however detract from the fact that sources of infection rich in spores such as plants and soil should be banned from the sick-room. In intensive care units, regular screening for airborne moulds is advised. There are various forms of apparatus for quantifying moulds in the air. It should be realised that elimination of moulds from a room is only possible with the use of a laminar flow unit.

Preventive treatment should be instituted for certain categories of risk patients e.g. a patient with neutropenia and fever which does not respond to 4-6 days of antibiotic therapy has a 20% chance of having a deep mycosis with Aspergillus (or Candida) and should be treated with ampho B until the time that neutrophil numbers are restored to normal levels.

As in other deep mycoses, the host’s resistance plays an important role in the pathogenesis. Deep candidoses occur only in predisposed patients. Local or general predisposing factors are initially responsible for the increased colonisation of the mouth and intestine, and subsequently for possible invasion and spread. In animals and even in humans it has been clearly demonstrated that if large quantities of yeast cells are given orally, they are subsequently found in the blood. This physiological passage from the intestine is known as persorption. It is highly probable that persorption and not an exogenous infection, is at the origin of most cases of deep candidosis.

The majority of systemic candidioses are caused by C. albicans. Other species are C. parapsilosis, C. tropicalis, C. krusei, C. guilliermondii, C. kefyr, C. lusitaniae, C. zeylanoides and C. glabrata. The aetiology varies between patients.

The localisations and the symptoms in deep candidosis are markedly patient-related. Allowance must be made for this patient-candidosis inter-relationship when interpreting serological tests or evaluating treatment with antifungal agents.

Oesophagitis and colitis develop when Candida multiply in the digestive tract as a consequence of a disturbance of the intestinal flora following antibiotic administration. Pulmonary candidosis may be the consequence of haematogenous spread in risk patients and sometimes of direct colonisation via the airways. In systemic deep candidosis there are practically always localisations in the kidneys, as well as in the eyes and elsewhere.

Skin lesions are sometimes an early sign of systemic candidosis.

Chronic disseminated candidosis, with the formation of several small abscesses in the liver and spleen and sometimes in the kidneys, is a clinical condition that occurs predominantly in leukaemia patients after a long period of neutropenia. Endocarditis due to Candida can occur after bacterial endocarditis or after heart surgery (valve prosthesis). Meningitis due to Candida is sometimes found in premature infants. A particular clinical presentation has been described since the 1980s in heroin users: formation of pustular and nodular lesions principally on the hairy skin of the head (which disappear after about 4 weeks and result in alopecia) and in the beard area. In about 50% of cases they are followed a few weeks/months later by ocular lesions (chorioretinitis/vitritis) and osteo-articular and cardiac localisations.

As C. albicans is present in the mouth and the intestine of all people, direct examination - presence of yeast cells and yeast threads – is of much greater value than culture. In this last case, a quantitative growth assessment should be made (e.g. in faeces ³ 10⁶ CFU/g). The isolation of Candida from normally sterile samples (such as cerebrospinal fluid) is always significant. In some patients the diagnosis is made histologically. The detection of antibodies to Candida is only of value if titres can be compared before and during the infection. The detection of certain metabolites and in particular of specific antigens is of greater diagnostic value. However, the sensitivity and the specificity of the available tests are the subject of discussion.

In various forms of deep candidosis, the blood cultures can sometimes remain negative. On the other hand, a single positive blood culture is not without significance. In some patients, unifocal candidosis is found weeks/months after "transient" candidaemia (osteomyelitis, sometimes kidney abscess and even endocarditis).

The choice of antifungal agent, azole or amphotericin B, is dependent on the type of patient, the species and the severity of the infection. Thus, C. krusei is usually resistant to fluconazole and C. lusitaniae to amphotericin B.

IDSA (Inf. Dis. Soc. Amer.) working group

*Species is known

• Amphotericin B 0.6 mg/kg/day or
• Fluconazole 6 mg/kg/day
• depending on the severity of the infection.

• Amphotericin B (>0.7 mg/kg/day) or
• Fluconazole (12 mg/kg/day)
• depending on the severity of the infection.

Treatment is continued for 2 weeks after the last positive blood culture and/or the disappearance of the symptoms. In patients who show an improvement, it is possible to switch from amphotericin B to fluconazole.

• Amphotericin B (>0.7 mg/kg/day)
• Fluconazole (>6 mg/kg/day)
• depending on the stability of the patient’s condition.

This is a mycosis caused by an exosaprophytic yeast, Cryptococcus neoformans. There are two varieties, C. neoformans var. neoformans and C. neoformans var. gattii, which are distinguished on the basis of serological, morphological, physiological and epidemiological characteristics. The variety neoformans is cosmopolitan and is often isolated from the environment, particularly from pigeon droppings. The variety gattii is exclusively tropical and to date has never been isolated from bird droppings. Both have been shown to grow on trunks of tropical trees such as Eucalyptus. This wood probably represents the natural biotope of both varieties.

Cryptococcosis occurs only exceptionally in people with normal resistance. The majority of cases occur in patients with impaired cell immunity.

Cryptococcosis is a frequent infection in AIDS patients, particularly in Central Africa, in some regions of South America and in Southeast Asia (20-25% of AIDS patients). This high prevalence, as has recently been demonstrated, is probably the consequence of frequent contact with the variety neoformans in the environment (even in houses).

The great majority of cases (>99%) are caused by the variety neoformans and not by the (sub)tropical variety gattii.

The portal of entry is the airways, but pure pulmonary cryptococcosis is observed only exceptionally. Pulmonary localisations are usually found in systemic cryptococcosis. From the lungs, dissemination can occur to the central nervous system with the occurrence of chronic meningitis.

In patients with severe abnormalities of cellular immunity such as AIDS patients, there is often dissemination to multiple foci, including the prostate. Primary cutaneous cryptococcosis (the skin as the portal of entry) is extremely rare. In most cases, infection of the skin should be considered as secondary. If it is primary there are no circulating antigens present and usually serotype D is involved.

If cryptococcal meningitis is suspected, the cerebrospinal fluid can be centrifuged and a drop of the sediment mixed with diluted India ink (1 part ink/1 part water). The thick mucopolysaccharide capsule then becomes clearly visible. For culture, Sabouraud is used without actidione. There are special media (Niger or Guizotia abyssinica) on which C. neoformans forms brown colonies.

There are now a number of reliable commercial kits (agglutination and latex tests) for the detection of C. neoformans antigens in cerebrospinal fluid and serum. This examination has both a diagnostic and a prognostic value. Titres fall at the beginning of therapy. For histological examination, mucicarmine is preferred, which stains the capsule, in combination with silver impregnation (Gomori-Grocott), which stains the yeast wall.

• Ampho B (0.5-0.8 mg/kg/day) IV followed by fluconazole 400 mg/day for 8-10 weeks

or

• Ampho B (0.3 mg/kg/day) IV + 5-fluorocytosine (37.5 mg/kg 4x/day PO for 6 weeks)

or

• Fluconazole (400 mg/d) IV or orally for 8 weeks (mild infection)

• Ampho B (0.5-0.8 mg/kg/day) IV + 5-fluorocytosine (37.5 mg/kg 4x/day) orally until no more fever and negative culture of cerebrospinal fluid (6 weeks), thereafter fluconazole 200 mg/day orally.

or

• Fluconazole (400 mg/day) PO for 8-10 weeks (mild infection)

• Ampho B (0.7-1.0 mg/kg/day) IV + ?5-FC (25 mg/kg 4x/day) (5-FC is toxic to AIDS patients) orally until stabilisation (2 weeks), then fluconazole 400 mg/day PO for 10 weeks, thereafter 200 mg/day lifelong.

The exosaprophytic moulds that cause exotic deep mycoses have the lungs as their portal of entry. They are dimorphic, i.e. they occur in two forms. In the environment they are filamentous, while in vivo they exhibit another morphology that of yeasts. These moulds are capable of causing disease in patients without predisposing factors. The severity of the condition varies according to the inoculum and the patient’s immune status. In patients without predisposing factors dissemination is rare and associated with a very large inoculum. In risk patients (AIDS), however, dissemination always occurs, even if only a small number of spores are inhaled. Dissemination leads to the secondary form in which numerous deep foci are possible and cutaneous lesions are also often observed.

The laboratory diagnosis is based on the specific morphology which the pathogen exhibits in vivo and on the culture of the saprophytic phase. Manipulation of the cultures is dangerous! There are reliable serological tests which are of diagnostic and prognostic value. For therapy, as an alternative to amphotericin B, use is increasingly, and successfully, being made of the azoles (itraconazole), particularly for the secondary chronic forms or relapse prevention (cf. cryptococcosis).

This mycosis occurs primarily in the southeast of the USA, but is not exclusively North American. Native cases also occur in South America, Africa and Asia. Apart from a handfull of Romanian and Italian cases those found in Europe have been imported.

The causative agent, Histoplasma capsulatum var. capsulatum, is an exosaprophytic mould that is isolated in the USA from various biotopes such as chicken manure, soil under starling roosts, seagull breeding sites and bat guano in caves (cave disease or speleologist’s disease).

The filamentous phase is found in the environment or in culture at 25°C, characterised by round spores with a thick wall, surrounded by protrusions (chlamydospores) and small round spores with a smooth wall. In vivo, in the parasitic phase, small, ovoid yeasts of 3-4 µm are found in the cells of the RES (histiocytes, monocytes).

'The syphilis of the fungus world’, meaning that histoplasmosis is one of the "Great Imitators". Histoplasmosis has been described as an illustration of the large variety of clinical forms.

In most cases, after contact with a low dose, an asymptomatic infection (99%) is seen or a self-limiting flu syndrome occurs (1%).

At high inocula or with temporary suppression of immunity an acute pulmonary disease can occur. After recovery calcifications in the lung and lymph nodes are seen in 1/3 of cases after 1-2 years.

A chronic mild form is described in adults in the event of a temporary suppression of cellular immunity. This involves an endogenous re-activation, as in ex-colonial soldiers, 10-20 years after they have returned from Africa, South America or Asia, or a re-infection in people still living in endemic areas. Oropharyngeal and nasal lesions and lesions of the vocal chords closely resembling malignant cells (nodules, ulcerations) and which may be associated with dysphagia and dysphonia are seen. In 50% of cases the adrenal glands are also involved. Systemic histoplasmosis is described in AIDS patients, sometimes with very severe cutaneous and mucosal lesions, as well as a possible cerebral involvement (meningitis). It results in a systemic granulomatous disease, with preferential lesions on lips and in the adrenals.

The diagnosis of histoplasmosis is made by direct examination of the parasitic phase (yeast) in sputum, bone marrow or blood. Histoplasma can also be found in histological preparations in RES cells. The intradermal reaction with histoplasmin is of no diagnostic value. The serological tests (immunodiffusion and complement fixation) are based on the detection of specific antibodies and recently on the detection of specific antigens (RIA). Both variants of H. capsulatum are level 3 pathogens and should only be cultured in a laboratory with the appropriate security clearance.

African histoplasmosis is geographically confined to Central Africa. Although it is established that the pathogen is also an exosaprophytic mould, the natural biotope remains unknown.

In the parasitic phase, H. capsulatum var. duboisii exhibits large, round spores of 10-15 µm. In the saprophytic phase, the two varieties are morphologically indistinguishable.

Patients with this chronic mycosis always exhibit polymorphous cutaneous lesions, bone and lymph node involvement and ultimately random deep localisations. When the disease follows an acute course (e.g. in AIDS patients), the yeast cells remain small and the infection is usually ascribed mistakenly to the variety capsulatum. In experimental infections also, cells exceeding the variety capsulatum in size are found only after a long time.

This mycosis only occurs in Southeast Asia and is usually associated with suppression of cellular immunity. The pathogen P. marneffei was first isolated from bamboo rats in Vietnam and has since been found in patients with a disseminated, often fatal mycosis. The disease is an AIDS indicator.

Penicillium marneffei is a dimorphic mould. It is the only Penicillium species that can cause invasive disease. In the saprophytic phase it is a common Penicillium which produces a red pigment that diffuses in agar. In the parasitic phase, intrahistiocytic and intramacrophagic elements are found which divide by fission and not by bud formation.

The portal of entry is the lung and the infection spreads rapidly or otherwise via the RES. In AIDS patients, fever, marked weight loss, hepatosplenomegaly and often also cutaneous lesions are seen. DD with cryptococcosis, histoplasmosis.

The diagnosis of this mycosis is based on direct examination of sputum, BAL, bone marrow and material from skin lesions or on histological examination, where the intrahistiocytic elements can be observed. P. marneffei can be cultured but the manipulation should be performed in a level 2 laboratory. Reliable serological tests are being developed.

The disease is endemic in the wilderness areas of the southwest of the United States. In addition, foci have been described in Central and South America. Despite the pathogenicity of all Coccidioides immitis strains, it is estimated that only 0.2% of cases showed symptoms of deep localisations and/or skin granulomas in the period before 1990. Since then the number of cases has steadily increased, not only because of the AIDS epidemic, but also as a result of earthquakes and sandstorms (disturbance of soil structure).

Coccidioides immitis is a dimorphic mould found in its filamentous phase in soil. The pathogenic spores are easily dispersed from dry ground or material. In vivo (parasitic phase) no yeasts are found, but instead spherules, large, spherical elements of 20-80 µm diameter. These spherules contain numerous endospores.

60% of those infected exhibit no symptoms or only minor respiratory disorders. These people are coccidioidin-positive. Approximately 40% go on to develop lower respiratory tract infections after 1-3 weeks, sometimes with erythema nodosum or erythema multiforme. The fungus can be spontaneously eliminated but it is preferable to administer azoles. About 5% of patients retain cavities and nodules in their lungs. Exceptionally in people with a normal immune system –but in 100% of AIDS patients- an extrapulmonary form is found with meningitis and bone involvement.

Spherules are found on direct or histological examination. The culture is relatively atypical and should only be performed in a level 3 laboratory. The coccidioidin skin test can be used for people who suffer a primary infection but anergy is possible in progressive disease. Spherulin is supposedly more sensitive. No cross-reactions have been described. There are other serological tests (latex agglutination, immunodiffusion, complement fixation, ELISA) for the detection of antibodies.

Paracoccidioidomycosis or South American blastomycosis occurs in discrete foci in Latin America. It is thought that the fungus (Paracoccidioides brasiliensis) exists in the soil as a mold, with infections happening through the inhalation of conidia (spores). These spores convert into yeasts in the lungs and are then thought to spread to other sites haematogeneously and via the lymphatics. Most primary infections are self-limiting. The organism has the ability to remain dormant in the human host for long periods. It can cause clinical disease at a later time if host defences would become impaired (e.g. depression of cell mediated immune responses). Overt infection results in a progressive mycosis with lesions of the skin, mucous membranes (especially mouth, lips and nose) and internal organs. Long asymptomatic periods enable patients to travel far from endemic areas before developing clinical problems. Lesions in the face, naso- and oropharynx resemble espundia (mucocutaneous leishmaniasis), lupus vulgaris (skin tuberculosis) and syphilis. Papules will ulcerate and enlarge both peripherally and deeper into the subcutaneous tissue. A hard hyperkeratotic border may surround a deep ulcerating crater on the skin. Extensive coalescent ulcerations may eventually result in the destruction of the uvula, epiglottis and vocal cords. Eating and drinking become difficult and painfull. Lymphatic infections lead to painless enlargement of cervical, supraclavicular and/or axillary nodes. Draining sinuses may form. Visceral lesions in liver, spleen and lymph nodes can lead to abdominal pain, hepatosplenomegaly and low-grade fever. Pulmonary involvement occasionally leads to mild symptoms, including cough and sputum production, although the radiograph of the chest can show dramatic involvement of the lungs. Infections tend to be very chronic, but not fatal. Diagnosis relies on demonstration of the yeasts in tissue/secretions. The yeasts are usually abundantly present in the bases and edges of slowly expanding ulcera. In tissue specimens, the yeasts are rather large (15 µm) with multiple buds, thereby resembling the steering wheel of a boat. Gomori staining of biopsies is useful. Serology by immunodiffusion is positive in ± 98% of cases. Azoles such as itraconazole are usually very effective as treatment. Amphotericin B can be used if there is no success with oral itraconazole. Sulfonamides can be used, but have only moderate activity and should be administered for very long periods.

The term mucormycosis (Lat. mucor = mold) is applied to opportunistic infections caused by the genera Rhizopus, Rhizomucor, Mucor, Absidia and Cunninghamella, but also species belonging to Apophysomyces and Saksanaea are occasionally responsable. The genus Mortierella is of doubtful pathogenicity. Of the Rhizopus species, the most common agent is Rhizopus arrhizus (Rhizopus oryzae). Rhizopus and Rhizomucor species are ubiquitous, appearing on decaying vegetation, dung and foods with high sugar content. Predisposing conditions include diabetic ketoacidosis, chronic renal failure and treatment with cytotoxic drugs and steroids. Long-term treatment with deferoxamine is a risk factor for mucormycosis of sinuses or lungs. Widely disseminated disease can occur in people with very low resistance, e.g. after aggressive chemotherapy and deep neutropenia. Invasive disease of the sinuses, orbits and lungs can occur. Low-grade fever, dull sinus pain, nasal congestion and bloody discharge from the nose occur. Chemosis and proptosis follow. The diagnosis should be considered in acidotic diabetic patients with necrotic lesions of the nose/sinuses (turbinates!) or with recent cranial nerve abnormalities, especially oculomotor, trochlear or abducens paralysis (diploplia!). Meningeal invasion and infiltration into the frontal lobe can ensue in these patients. A midline lesion on the hard palate can occur. Invasion of the lung resembles a severe bacterial or mycobacterial pneumonia. Biopsy with culture is required for diagnosis and species identification. Cultures can be negative however, since non-septate hyphae are more fragile than septate organisms. Rhizopus oryzae is the most frequent infectious agent reported, followed by R. microsporus var. rhizopodiformis, Absidia corymbifera and Rhizomucor pusillus. These four species account for more than 80% of culture-proven cases of zygomycosis. The fungi appear in tissues as broad, nonseptate hyphae of uneven diameter (diameter ranging from 6 to 50 µm). Treatment is based on administration of amphotericin B (classic or liposomal forms). Azoles are of no value in the treatment of mucormycosis. Control of the diabetes is essential. Surgical removal of necrotic tissue (debridement) should not be delayed. There is a high mortality and survival for more than two weeks is unusual.

Blastomycosis -also known as North American blastomycosis or Gilchrist's disease- occurs in a geographically limited area of the south central and midwestern USA, upstate New York and southern Canada. A few cases have been described from Africa, the Middle East, India and Mexico. The fungus occurs in soil enriched with animal excreta and moist, acid, decaying organic material. Infection follows the inhalation of conidia (asexual spores) of Blastomyces dermatitidis. Both man and dogs can be infected. The spores will convert into yeasts, which will invade the lungs and occasionally spread haematogeneously to several organs, especially skin, bone or urogenital system. Pulmonary infection can be asymptomatic. Genital involvement such as chronic epididymitis, mimicks tuberculosis. Cough, low to moderate fever, dyspnoea and chest pain, purulent/bloody sputum, pleural fluid, weight loss and prostatration occur in symptomatic patients. Radiological studies usually reveal pulmonary infiltrates and enlarged hilar lymph nodes. Progressive pulmonary blastomycosis resembles tuberculosis or a neoplasm. Raised single or multiple verrucous cutaneous lesions that tend to have an abrupt downward sloping red-purplish border are usually present in disseminated blastomycosis. The border extends slowly, leaving a central atrophic scar. Those skin lesions can resemble skin cancer. Bones such as ribs and vertebrae are frequently affected (25-75%). Lesions appear both destructive and proliferative on radiography. Central nervous system lesions are uncommon. Acute self-limiting blastomycosis is rarely diagnosed. The organism is found in clinical specimens as a thick, double-walled cell, 5-20 µm in diameter, sometimes even reaching 30 µm. Some yeast cells have a single bud. Definite identification is via culture but detection of the above mentioned yeast cells in pus, sputum or urine is very suggestive. Gomori's methenamine silver stain and PAS staining are useful for biopsies. Serology is not really useful. Untreated disseminated blastomycosis is usually progressive and can be fatal. Itraconazole (200-400 mg/day) is used as a first-choice treatment. If no improvement occurs, one can give 800 mg itraconazole per day or switch over to IV amphotericin B. Follow-up in order to identify a relaps should continue for several years.

Infections with Scedosporium prolificans, a fungus closely related to P. boydii, can cause infections in joints, bones, or soft tissue, usually following trauma. These infections are best treated with surgical debridement. Infections in immunosuppressed persons can be fatal.

As well as being a common contaminant and a plant pathogen, Fusarium sp. may cause various infections in humans. Existence of Fusarium in hospital water distribution systems may result in disseminated fusariosis in immunosuppressed patients. Fusarium which exist in soil of potted plants in hospitals constitute a hazardous mycotic reservoir for nosocomial fusariosis. Localised as well as disseminated infections occur. Widespread infections are only encountered in patients with severe immunosuppression, such as haematological malignancy and deep neutropenia. Fever and myalgia is followed by skin lesions in 65% of cases. The -usually multiple- skin lesions resemble progressive ecthyma gangrenosum and tend to appear on arms and legs. A portal of entry is usually not apparent. Fusarium species are occasionally responsible for endocarditis. Other manifestations are keratitis, endophthalmitis, otitis media, onychomycosis, infections of burns, mycetoma, sinusitis, cystitis, pulmonary infections, peritonitis in peritoneal dialysis patients, central venous catheter infections and septic arthritis. The diagnosis is based on cultures and mycological identification. Amphotericin B is the treatment of choice, but Fusarium sp. are among the most drug-resistant fungi. Fusarium solani tends to be most resistant of all and tends to be the most virulent organism in this genus. Granulocyte and GM-CSF transfusions concommitant to amphotericin B therapy may be life-saving in some immunosuppressed patients with disseminated fusariosis. Posaconazole holds promise as a treatment, but further data are needed. Topical natamycin is used for treatment of Fusarium keratitis.