1. Subcutaneous Mycoses
• These are chronic, localized infections of the skin and subcutaneous tissue
following the traumatic implantation of the aetiologic agent.
• The causative fungi are all soil saprophytes of regional epidemiology whose
ability to adapt to the tissue environment and elicit disease is extremely variable.
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3. Chromoblastomycosis
• A mycotic infection of the cutaneous and subcutaneous tissues characterized by the development in
tissue of dematiaceous (brown-pigmented), planate-dividing, rounded sclerotic bodies.
• Infections are caused by the traumatic implantation of fungal elements into the skin and are chronic,
slowly progressive and localized.
• Tissue proliferation usually occurs around the area of inoculation producing crusted, verrucose, wart-
like lesions.
• World-wide distribution but more common in bare footed populations living in tropical regions.
• Aetiological agents include various dematiaceous hyphomycetes associated with decaying vegetation or
soil, especially Phialophora verrucosa, Fonsecaea spp., and Cladophialophora carrionii.
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4. Clinical manifestations:
• Lesions of chromoblastomycosis are most often found on exposed parts of the body and usually start a small scaly papules or
nodules which are painless but may be itchy.
• Satellite lesions may gradually arise and as the disease develops rash-like areas enlarge and become raised irregular plaques that are
often scaly or verrucose.
• In long standing infections, lesions may become tumorous and even cauliflower-like in appearance.
• Other prominent features include epithelial hyperplasia, fibrosis and microabscess formation in the epidermis.
• Chromoblastomycosis must be distinguished from other cutaneous fungal infections such as blastomycosis, lobomycosis,
paracoccidioidomycosis and sporotrichosis.
• It may also mimic protothecosis, leishmaniasis, verrucose tuberculosis, certain leprous lesions and syphilis.
• Mycological and histopathological investigations are essential to confirm the diagnosis.
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5. Clinical manifestations:
Chromic verrucous Chromoblastomycosis of the hand due C.carrionii
Tissue hyperplasia forming a white verrucoid cutaneous lesion. In Australia, chromoblastomycosis due to C.
carrionii occurs mostly on the hands and arms of timber and cattle workers in humid tropical forests.
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6. Laboratory diagnosis:
• Clinical material:
• Skin scrapings and/or biopsy.
• Direct microscopy:
• (a) Skin scrapings should be examined using 10% KOH and Parker ink or
calcofluor white mounts;
• (b) Tissue sections should be stained using H&E, PAS digest, and Grocott's
methenamine silver (GMS).
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7. Laboratory diagnosis:
• Interpretation:
• The presence in tissue of brown pigmented, planate-dividing, rounded sclerotic bodies
from a patient with supporting clinical symptoms should be considered significant.
• Remember direct microscopy or histopathology does not offer a specific identification of
the causative agent.
• Note: direct microscopy of tissue is necessary to differentiate between
chromoblastomycosis and phaeohyphomycosis where the tissue morphology of the
causative organism is mycelial.
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9. Laboratory diagnosis:
• Culture:
• Clinical specimens should be inoculated onto primary isolation media, like
Sabouraud's dextrose agar.
• Interpretation:
• The dematiaceous hyphomycetes involved are well recognized as environmental
fungi, therefore a positive culture from a non-sterile specimen, such as sputum or
skin, needs to be supported by clinical history and direct microscopic evidence in
order to be considered significant.
• Culture identification is the only reliable means of distinguishing these fungi.
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11. Laboratory diagnosis…
• Serology:
• There are currently no commercially available serological procedures for the diagnosis of
chromoblastomycosis.
• Identification:
• Culture characteristics and microscopic morphology are important, especially conidial morphology,
the arrangement of conidia on the conidiogenous cell and the morphology of the conidiogenous
cell.
• Cellotape flag and/or slide culture preparations are recommended.
• Causative agents: Cladophialophora carrionii, Fonsecaea species complex, Phialophora
verrucosa
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12. Lobomycosis
• Lobomycosis is a chronic, localized, subepidermal infection characterized by the presence of
keloidal, verrucoid, nodular lesions or sometimes by vegetating crusty plaques and tumours.
• The lesions contain masses of spheroidal, yeast-like cells of Lacazia loboi.
• There is no systemic spread.
• The disease has been found in humans and dolphins and is restricted to the Amazon Valley in
Brasil.
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13. Clinical manifestations:
• The initial infection is thought to be caused by traumatic implantation such as an arthropod sting,
snake bite, sting-ray sting, or wound acquired while cutting vegetation.
• The lesions begin as small, hard nodules resembling keloids and may spread slowly in the dermis
and continue to develop over a period of many years.
• Older lesions become verrucoid and may ulcerate.
• The disease may be transferred to other areas of the skin by further trauma or autoinoculation.
• Thus the areas of involvement may become quite extensive.
• Lesions are usually found on the arms, legs, face or ears.
• 90% of cases are men, mostly in farmers and other high risk groups exposed to various harsh
conditions as well as aquatic habitats.
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15. Laboratory diagnosis:
• Clinical material:
• Tissue sample obtained by curettage or surgical biopsy.
• Direct microscopy:
• (a) Tissue can be macerated and mounted in 10% KOH and Parker ink or calcofluor white
mounts or
• (b) Tissue sections should be stained using PAS digest, Grocott's methenamine silver (GMS)
or Gram stains.
• Interpretation:
• The presence of chains of darkly pigmented, spheroidal, yeast-like organisms tentatively
referred to as Loboa loboi is typical for lobomycosis.
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16. Laboratory diagnosis:
GMS stained tissue specimen showing numerous darkly pigmented yeast-like cells, often in chains, 9-12 um in size.
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17. Laboratory diagnosis:
• Culture:
• The aetiologic agent known as Lacazia loboi remains to be cultured.
• Serology:
• There are currently no serological tests available.
• Identification:
• Clinical features, geographic location and microscopic morphology are
important.
• Causative agents: Lacazia loboi
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18. Mycetoma
• A mycotic infection of humans and animals caused by a number of different fungi and
actinomycetes characterized by draining sinuses, granules and tumefaction.
• The disease results from the traumatic implantation of the aetiologic agent and usually involves the
cutaneous and subcutaneous tissue, fascia and bone of the foot or hand.
• Sinuses discharge serosanguinous fluid containing the granules which vary in size, colour and
degree of hardness, depending on the aetiologic species, and are the hallmark of mycetoma.
• World-wide distribution but most common in bare-footed populations living in tropical or
subtropical regions.
• Aetiological agents include Madurella, Acremonium, Scedosporium, Exophiala, Leptosphaeria,
Curvularia, Fusarium, Aspergillus etc.
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19. Mycetoma
• Mycetoma is a chronic, suppurative infection of the subcutaneous tissue and
contiguous bone.
• The clinical features are fairly uniform, regardless of the organism involved.
• The feet are the most common site for infection and account for at least two-thirds
of cases.
• Other sites include the lower legs, hands, head, neck, chest, shoulder and arms.
• Most cases start out as a small hard painless nodule which over time begins to
soften on the surface and ulcerate to discharge a viscous, purulent fluid containing
grains.
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20. Mycetoma
• The infection slowly spreads to adjacent tissue, including bone, often causing
considerable deformity.
• Sinuses continue to discharge serosanguinous fluid containing the granules which
vary in size, colour and degree of hardness, depending on the aetiologic species.
• These grains are the hallmark of mycetoma.
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21. Mycotic mycetoma
• Mycetoma showing numerous draining
sinuses.
• There is destruction of bone, distortion of the
foot, and hyperplasia at the openings of the
sinus tracts.
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22. Laboratory diagnosis:
• Clinical material:
• Tissue biopsy or excised sinus, serosanguinous fluid containing the granules
which vary in size, colour and degree of hardness, depending on the aetiologic
species.
• Direct microscopy:
• Serosanguinous fluid containing the granules should be examined using either
10% KOH and Parker ink or calcofluor white mounts, and tissue sections
should be stained using H&E, PAS digest, and Grocott's methenamine silver
(GMS).
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23. Laboratory diagnosis…
• Interpretation:
• The presence of white to yellow or black pigmented grains, from a patient with
supporting clinical symptoms should be considered significant.
• Biopsy and evidence of tissue invasion is of particular importance. Remember
direct microscopy or histopathology does not offer a specific identification of
the causative agent.
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25. Laboratory diagnosis…
• Culture:
• Clinical specimens should be inoculated onto primary isolation media, like SDA.
• Serology:
• There are currently no commercially available serological procedures for the diagnosis of
mycetoma.
• Identification:
• Characteristic clinical, microscopic and culture features.
• Causative agents:
• Acremonium sp., Aspergillus nidulans, Trematosphaeria grisea, Madurella mycetomatis,
Scedosporium apiospermum.
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26. Phaeohyphomycosis
• A mycotic infection of humans and lower animals caused by a number of dematiaceous (brown-
pigmented) fungi where the tissue morphology of the causative organism is mycelial.
• This separates it from other clinical types of disease involving brown-pigmented fungi where the
tissue morphology of the organism is a grain (mycotic mycetoma) or sclerotic body
(chromoblastomycosis).
• The etiological agents include various dematiaceous hyphomycetes species of Exophiala,
Phialophora, Exserohilum, Cladophialophora, Verruconis, Aureobasidium, Cladosporium,
Curvularia and Alternaria.
• Ajello (1986) listed 71 species from 39 genera as causative agents of phaeohyphomycosis.
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27. Phaeohyphomycosis…
• Clinical manifestations:
• Clinical forms of phaeohyphomycosis range from localized superficial
infections of the stratum corneum (tinea nigra) to subcutaneous cysts
(phaeomycotic cyst) to invasion of the brain.
• Subcutaneous phaeohyphomycosis
• Paranasal sinus phaeohyphomycosis:
• Cerebral phaeohyphomycosis:
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28. Subcutaneous phaeohyphomycosis:
• Subcutaneous infections occur worldwide,
• Usually following the traumatic implantation of fungal elements from
contaminated soil, thorns or wood splinters.
• Exophiala jeanselmei and Wangiella dermatitidis are the most common agents
• Cystic lesions occur most often in adults.
• Occasionally, overlying verrucous lesions are formed, especially in the
immunosuppressed patient.
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30. Subcutaneous phaeohyphomycosis:
• Paranasal sinus phaeohyphomycosis:
• Sinusitis caused by dematiaceous fungi, especially species of Exserohilum, Curvularia and
Alternaria is increasingly being reported, especially in patients with a history of allergic
rhinitis or immunosuppression.
• Cerebral phaeohyphomycosis:
• is a rare infection, occurring mostly in immunosuppressed patients following the inhalation of
conidia.
• However, cerebral infections caused by Cladophialophora bantiana have been reported in a
number of patients without any obvious predisposing factors.
• This fungus is neurotropic and dissemination to sites other than the CNS is rare.
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31. Laboratory diagnosis:
• Clinical material:
• Skin scrapings and/or biopsy; sputum and bronchial washings; cerebrospinal fluid, pleural
fluid and blood; tissue biopsies from various visceral organs and indwelling catheter tips.
• Direct microscopy:
(a) Skin scrapings, sputum, bronchial washings and aspirates should be examined using 10%
KOH and Parker ink or calcofluor white mounts;
(b) Exudates and body fluids should be centrifuged and the sediment examined using either
10% KOH and Parker ink or calcofluor white mounts,
(c) Tissue sections should be stained using H&E, PAS digest, and Grocott's methenamine silver
(GMS)
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32. Laboratory diagnosis:
Figure: H&E stained section showing characteristic, brown-pigmented, septate hyphal elements of Exophiala
jeanselmei.
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Interpretation:
The presence of brown pigmented, branching septate hyphae in
any specimen, from a patient with supporting clinical symptoms
should be considered significant. Biopsy and evidence of tissue
invasion is of particular importance. Remember direct
microscopy or histopathology does not offer a specific
identification of the causative agent.
Note:
Direct microscopy of tissue is necessary to differentiate between
chromoblastomycosis which is characterized by the presence in
tissue of brown pigmented, planate-dividing, rounded sclerotic
bodies and phaeohyphomycosis where the tissue morphology of
the causative organism is mycelial.
33. Laboratory diagnosis:
• Culture: Clinical specimens should be inoculated onto primary isolation media, like SDA
• Interpretation:
• The dematiaceous hyphomycetes involved are well recognized as common environmental
airborne contaminants
• Therefore, a positive culture from a non-sterile specimen, such as sputum or skin, needs to be
supported by direct microscopic evidence in order to be considered significant.
• A supporting clinical history in patients with appropriate predisposing conditions, is also
helpful.
• Culture identification is the only reliable means of distinguishing these fungi.
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35. Rhinosporidiosis
• Rhinosporidium seeberi, first described by Malbran in 1892, is the causative agent of
Rhinosporidiosis, a chronic subcutaneous mycosis.
• The infection is characterized by formation of polypoid masses at nasal mucosa, conjunctiva,
genitalia, and rectum.
• Fish and aquatic insects are the natural reservoirs of R. seeberi.
• The taxonomic classification of R. seeberi has long been controversial so far and has been based
solely on morphological properties.
• Microscopically, R. seeberi produces spherules in infected tissue and these spherules are filled with
endospores.
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36. Rhinosporidiosis…
• Most interestingly, and complicating the issue, this microorganism cannot be
cultured in vitro on artificial media.
• Based on these findings, while some investigators classified it as an ascomycetous
fungus, others preferred the term "fungus-like".
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38. Sporotrichosis
• Sporotrichosis is primarily a chronic mycotic infection of the cutaneous or
subcutaneous tissues and adjacent lymphatics
• Characterized by nodular lesions which may suppurate and ulcerate.
• Infections are caused by the traumatic implantation of the fungus into the skin, or
very rarely, by inhalation into the lungs.
• Secondary spread to articular surfaces, bone and muscle is not infrequent, and the
infection may also occasionally involve the central nervous system, lungs or
genitourinary tract.
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39. Clinical manifestations:
• Fixed cutaneous sporotrichosis:
• Primary lesions develop at the site of implantation of the fungus, usually at
more exposed sites mainly the limbs, hands and fingers.
• Lesions often start out as a painless nodule which soon become palpable and
ulcerate often discharging a serous or purulent fluid.
• Importantly, lesions remain localized around the initial site of implantation
and do not spread along the lymphangitic channels.
• Isolates from these lesions usually grow well at 35C, but not at 37C.
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41. Lymphocutaneous sporotrichosis:
• Primary lesions develop at the site of implantation of the fungus
• secondary lesions also appear along the lymphangitic channels which follow the
same indolent course as the primary lesion
• start out as painless nodules which soon become palpable and ulcerate.
• No systemic symptoms are present.
• Isolates from these lesions usually grow well at both 35C and 37C.
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42. Lymphocutaneous sporotrichosis
Lymphocutaneous sporotrichosis showing typical elevated
subcutaneous nodules developing along the regional
lymphatics of the forearm.
Lymphocutaneous sporotrichosis showing more
advanced, ulcerating lesions developing along the lymph
system of the forearm.
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43. Pulmonary sporotrichosis:
• This is a rare entity usually caused by the inhalation of conidia but cases of
haematogenous dissemination have been reported.
• Symptoms are nonspecific and include cough, sputum production, fever,
weight loss and upper-lobe lesion.
• Haemoptysis may occur and it can be massive and fatal.
• The natural course of the lung lesion is gradual progression to death.
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44. Osteoarticular sporotrichosis:
• Most patients also have cutaneous lesions and present with stiffness and pain
in a large joint, usually the knee, elbow, ankle or wrist.
• Osteomyelitis seldom occurs without arthritis;
• the lesions usually confined to the long bones near affected joints.
• Other rare forms of sporotrichoisis include endophthalmitis, chorioretinitis and
meningitis.
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45. Laboratory diagnosis:
• Clinical material: A tissue biopsy is the best specimen.
• Direct microscopy: Tissue sections should be stained using PAS digest, Grocott's methenamine
silver (GMS) or Gram stain.
• Interpretation:
• Look for small narrow base budding yeast cells (2-5um).
• Note they are often present in very low numbers and may be difficult to find.
• PAS and GMS stains are essential.
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46. Laboratory diagnosis…
Section from a fixed cutaneous lesion showing round Periodic Acid-Schiff (PAS) positive budding yeast-like cells.
Sporothrix schenckii is a dimorphic fungus and this is the typical yeast-like form seen in tissue.
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47. Laboratory diagnosis…
• Culture:
• Clinical specimens should be inoculated onto primary isolation media, like SDA and BHI agar
supplemented with 5% sheep blood.
• Interpretation:
• A positive culture from a biopsy should be considered significant.
• Serology: Serological tests are of limited value in the diagnosis of Sporotrichosis.
• Identification:
• Hyphomycete characterized by thermal dimorphism and clusters of ovoid, denticulate conidia
produced sympodially on short conidiophores.
• Causative agents: Sporothrix schenckii complex.
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48. Zygomycosis
• The term zygomycosis describes in the broadest sense any infection due to a
member of the Zygomycetes.
• These are primitive, fast growing, terrestrial, largely saprophytic fungi with a
cosmopolitan distribution.
• To date, some 665 species have been described
• Infections in humans and animals are generally rare
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49. Zygomycosis …
Zygomycetes
Order Mucorales Order Entomophthorales
4/1/2023 49
• Acute
• Medically important genera include:
• Rhizopus, Lichtheimia, Rhizomucor, Mucor,
Cunninghamella, Saksenaea, Apophysomyces,
Cokeromyces and Mortierella
• Chronic
• Conidiobolus
• Basidiobolus
50. Clinical manifestations:
• Zygomycosis in the debilitated patient is the most acute and fulminate fungal
infection known.
• The disease typically involves the rhino-facial-cranial area, lungs,
gastrointestinal tract, skin, or less commonly other organ systems.
• It is often associated with acidotic diabetes, starvation, severe burns, IVD user,
and leukemia and lymphoma, immunosuppressive therapy, or the use of
cytotoxins and corticosteroids, therapy with desferrioxamine (an iron chelating
agent for the treatment of iron overload) and other major trauma.
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51. Clinical manifestations…
• The infecting fungi have a predilection for invading vessels of the arterial system,
• Causing embolization and subsequent necrosis of surrounding tissue.
• A rapid diagnosis is extremely important if management and therapy are to be
successful.
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52. Fungi causing Subcutaneous Zygomycosis
• Zygomycosis
• Order Mucorales
• Acute
• Order Entomophthorales
• Chronic
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53. Zygomycosis (Mucorales).
• Mucorales infections Definition:
• Angiotropic (blood vessel-invading)
• The most common genera causing disease are:
• Rhizopus
• Rhizomucor
• Mucor
• Absidia
• Fast growing non-septate molds
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54. Zygomycosis
• Geographical distribution & normal habitat
• World-wide
• Soil and decomposing organic matter
• Found in outdoor and indoor air
• Food and dust
• Clinical forms: The infection typically involves the:
• Rhino-facial-cranial area
• Lungs, gastrointestinal tract or skin
• Other parts can also be affected
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55. Risk factors
• The disease is associated with:
• Diabetic ketoacidosis
• Malnourished children
• Severely burned patients
• It is also seen in patients with
• Leukemia
• Lymphoma
• AIDS
• In patients using corticosteroids
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56. Laboratory diagnosis
• Specimens:
• Aspirated material from sinuses
• Sputum in pulmonary disease
• Biopsy material
• Management of mucormycosis
• The prognosis is bad
• Most cases of gastric and pelvic disease are diagnosed at autopsy
• Cases occurred in patients with pulmonary disease, leukemia, or with lymphomas, are usually fatal
• Control of the diabetes, aggressive surgical debridement of involved tissue, and high doses of
Amphotericin B are recommended
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57. Zygomycosis Order Entomophthorales
• Entomophthorales infections: Causes subcutaneous zygomycosis
• Known as Entomophthoromycosis
• Two genera are involved:
• Conidiobolus
• Basidiobolus
• Infections are:
• Chronic
• Slowly progressive
• Restricted to the subcutaneous tissue
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58. Entomophthoromycosis
• Not like Mucorales:
• No vascular invasion or infarction
• Chronic inflammatory response
• Basidiobolus infection
• Chronic inflammatory or granulomatous disease
• Subcutaneous tissue of the limbs, chest, back or buttocks
• Mostly in children (predominance in males)
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59. Entomophthoromycosis…
• Conidiobolus infection
• Chronic inflammatory or granulomatous disease
• Nasal submucosa
• Characterized by polyps or palpable subcutaneous masses
• Occur mainly in adult (80% of cases)
• Laboratory diagnosis
• Specimens:
• Aspirated material from sinuses
• Biopsy material
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60. Laboratory diagnosis
• The following steps are used for the both types of Zygomycosis:
• Microscopy: 10 or 20% KOH:
• Typically contain thick-walled aseptate hyphae
• Swollen cells (up to 50 um) and distorted hyphae may be present
• Culture: SDA without cycloheximide at 30°C
• Rapid growth
• A diagnosis can also be made by examining a biopsy for granuloma formation and the presence of
aseptate hyphae, eosinophils, neutrophils, and fibroblasts.
• Tissue for culture should be send in a dry sterile container, and biopsies should be fixed and send in
formal saline.
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63. Laboratory diagnosis
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Non-septate (coenocytic) hyphal strand characteristic of
the fungi belonging to the Zygomycetes
Wide, sparsely-septate hyphae and striated sporangiospores
64. Rhinocerebral zygomycosis:
• Predisposing factors include
• uncontrolled diabetes mellitus or acidosis,
• steroid induced hyperglycemia, especially in patients with leukemia and lymphoma,
• renal transplant and concomitant treatment with corticosteroids and azathioprine
• Infections usually begin in the paranasal sinuses following the inhalation of
sporangiospores and may involve the orbit, palate, face, nose or brain.
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65. Pulmonary zygomycosis:
• Predisposing conditions include
• haematological malignancies, lymphoma and leukemia, or
• severe neutropenia,
• treatment with cytotoxins and corticosteroids, d
• esferrioxamine therapy;
• diabetes and organ transplantation.
• Infections result by inhalation of sporangiospores into the bronchioles and alveoli
• Leading to pulmonary infraction and necrosis with cavitation
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66. Gastrointestinal zygomycosis:
• A rare entity, usually associated with severe malnutrition, particularly in children,
and gastrointestinal diseases which disrupt the integrity of the mucosa.
• Primary infections probable result following the ingestion of fungal elements and
usually present as necrotic ulcers.
• Cutaneous zygomycosis:
• Local traumatic implantation of fungal elements through the skin, especially in patients with
extensive burns, diabetes or steroid induced hyperglycemia and trauma.
• Lesions vary considerably in morphology but include plaques, pustules, ulcerations, deep
abscesses and ragged necrotic patches.
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68. Disseminated zygomycosis:
• May originate from any of the above, especially in severely debilitated patients
with haematological malignancies, burns, diabetes or uraemia.
• Central nervous system alone:
• Intravenous drug abuse.
• Traumatic implantation leading to brain abscess.
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69. Laboratory diagnosis:
• Clinical material:
• Skin scrapings from cutaneous lesions;
• Sputum and needle biopsies from pulmonary lesions;
• Nasal discharges, scrapings and aspirates from sinuses in patients with
rhinocerebral lesions; and
• Biopsy tissue from patients with gastrointestinal and/or disseminated disease
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72. Laboratory diagnosis…
• Culture:
• Inoculate specimens onto primary isolation media, like Sabouraud's dextrose agar.
• Most zygomycetes are sensitive to cycloheximide (actidione) and this agent should not be used in culture
media.
• Look for fast growing, white to grey or brownish, downy colonies.
• Interpretation:
• Despite being recognized as common laboratory contaminants, zygomycetes are infrequently isolated in the
clinical laboratory.
• Therefore, in patients with any of the above predisposing conditions, especially diabetes or immunosuppression
and/or clinical symptoms, the isolation of any zygomycete fungus should be regarded as potentially significant.
• In patients without predisposing conditions, the isolation of a zygomycete from a non-sterile site, such as skin
or sputum, must be interpreted with caution, especially in the absence of direct microscopy.
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73. Laboratory diagnosis…
• Serology: There are currently no commercially available serological procedures for the diagnosis of
zygomycosis.
• Some laboratories have developed ELISA tests for the detection of antibodies to Zygomycetes.
• Identification:
• Zygomycetes are usually fast growing fungi characterized by primitive coenocytic (mostly
aseptate) hyphae.
• Asexual spores include chlamydoconidia, conidia and sporangiospores contained in sporangia
borne on simple or branched sporangiophores.
• Sexual reproduction is isogamous producing a thick-walled sexual resting spore called a
zygospore.
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74. Laboratory diagnosis…
• Most isolates are heterothallic i.e. zygospores are absent, therefore identification is based primarily
on sporangial morphology.
• This includes the arrangement and number of sporangiospores, shape, colour, presence or absence
of columellae and apophyses, as well as the arrangement of the sporangiophores and the presence
or absence of rhizoids.
• Growth temperature studies (25,37,45℃) can also be helpful.
• Tease mounts are best, use a drop of 95% alcohol as a wetting agent to reduce air bubbles.
• Laboratory identification of some zygomycetous fungi, especially Apophysomyces elegans and
Saksenaea vasiformis may be difficult or delayed because of the mold's failure to sporulate on the
primary isolation media or on subsequent subculture onto potato dextrose agar.
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75. Infections caused by entomophthoraceous fungi:
• Zygomycosis due to entomophthoraceous fungi:
• Caused by species of two genera Basidiobolus and Conidiobolus.
• Infections are
• Chronic
• slowly progressive and
• restricted to the subcutaneous tissue
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76. Zygomycosis due to entomophthoraceous fungi
• Not like Mucorales: Mucormycosis
• No vascular invasion or infarction
• Produce chronic inflammatory response(often with eosinophils and Splendore-Hoeppli
phenomena around the hyphae)
• Basidiobolus infection
• Chronic inflammatory or granulomatous disease
• Subcutaneous tissue of the limbs, chest, back or buttocks
• Mostly in children (predominance in males)
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77. Zygomycosis caused by Basidiobolus ranarum:
• This is a chronic inflammatory or granulomatous disease generally restricted to the
subcutaneous tissue of the limbs, chest, back or buttocks,
• primarily occurring in children and with a predominance in males.
• Initially, lesions appear as subcutaneous nodules which develop into massive,
firm, indurated, painless swellings which are freely movable over the underlying
muscle, but are attached to the skin which may become hyperpigmented but not
ulcerated.
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78. Zygomycosis caused by Basidiobolus ranarum
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Infections Are:
• Chronic
• Slow progressive
• Restricted to the subcutaneous tissue
79. Zygomycosis caused by Conidiobolus sp.:
• A chronic inflammatory or granulomatous disease
• Typically restricted to the nasal submucosa
• Characterized by polyps or palpable restricted subcutaneous masses
• Clinical variants, including pulmonary and systemic infections have also been described.
• Human infections occur mainly in adults with a predominance in males (80% of cases).
• Most cases have been reported from the tropical rain forest areas of central and west and south and
central America.
• Infections usually begin with unilateral involvement of the nasal mucosa.
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80. Zygomycosis caused by Conidiobolus sp.:
Zygomycosis caused by Conidiobolus
4/1/2023 80
• Symptoms include nasal obstruction, drainage and sinus pain.
• Subcutaneous nodules develop in the nasal and perinasal
regions and progressive generalized facial swelling may occur.
• Infections also occur in horses usually producing extensive
nasal polyps and other animals.
• Conidiobolus coronatus is also a recognized pathogen of
termites, other insects and spiders.
81. Laboratory diagnosis
• Clinical material: Skin biopsy tissue.
• Direct microscopy:
• Tissue sections should be stained with H&E and GMS.
• Examine specimens for broad, infrequently septate, thin-walled hyphae, which
often show focal bulbous dilations and irregular branching.
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82. Laboratory diagnosis…
• H&E stained section of infected tissue
showing broad, infrequently septate,
hyphae surrounded by an eosinophilic
sheath [Splendore-Hoeppli phenomena],
typical of zygomycosis caused by
Basidiobolus ranarum.
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The taxonomy of R. seeberi was studied in more detail recently by molecular phylogenetic analysis.
Interestingly, the results of these studies revealed that the sequence of 18S SSU rDNA from the R. seeberi isolates of two infected humans, a dog, and a swan proved to be identical to each other and related to a group of fish parasites.
Of note, R. seeberi was placed within the DRIP clade (Dermatocystidium, rosette agent, Ichtyophonus, and Psorospermium) in 1996. DRIP clade was later renamed as the class Ichtyosporea in 1998, and most recently as the class Mesomycetozoea in 2002. The class Mesomycetozoea includes a heterogeneous group of microorganisms that are at the animal-fungal boundary and consists of two orders; Dermocystida and Ichthyophonida.
While the microorganisms included in the order Dermocystida are either pathogens of fish (Dermocystidium spp. and the rosette agent) or of mammals and birds (R. seeberi), those in the order of Ichthyophonida are either pathogens of fish or are saprophytic microorganisms. Thus, R. seeberi now appears as the only microorganism that is classified in the class Mesomycetozoea and is pathogenic to mammals and birds.
Future studies will hopefully provide more information about the morphological features and pathogenicity of R. seeberi.
Warning: zygomycetous fungi have primitive coenocytic hyphae that will often be damaged and become non-viable during the biopsy procedure (especially scrapings and aspirates), or by the chopping up or tissue grinding process in the laboratory. This is why zygomycetous fungi that are clearly visible in direct microscopic or histopathological mounts are often difficult to grow in culture from clinical specimens.
If on clinical and/or radiological evidence zygomycosis is suspected then try to avoid excessive tissue damage when collecting the specimen and in the laboratory gently tease the tissue apart and inoculate it directly onto the isolation media.
If you are not sure hold the specimen in saline or BHI broth until the results of the direct microscopy or frozen histology sections are known. If zygomycetous hyphae are present proceed as above, otherwise homogenised the specimen and plate out.
