3. Opportunistic Systemic Mycoses
• These are fungal infections of the body which occur almost exclusively in
debilitated patients whose normal defence mechanisms are impaired.
• The organisms involved are cosmopolitan fungi which have a very low inherent
virulence.
• The increased incidence of these infections and the diversity of fungi causing
them, has paralleled the emergence of AIDS, more aggressive cancer and post-
transplantation chemotherapy and the use of antibiotics, cytotoxins,
immunosuppressives, corticosteroids and other macro disruptive procedures that
result in lowered resistance of the host.
4. Opportunistic Systemic Mycoses
Disease Causative organisms Incidence
Aspergillosis
Aspergillus fumigatus complex, A. flavus, complex, A.
terreus complex etc.
Common
Candidiasis
Candida, Debaryomyces, Kluyveromyces, Meyerozyma,
Pichia, etc.
Common
Cryptococcosis Cryptococcus spp. especially C. neoformans and C. gattii. Uncommon
Hyalohyphomycosis
Penicillium, Paecilomyces, Beauveria,
Fusarium, Scopulariopsis etc.
Rare
Phaeohyphomycosis Cladophialophora, Exophiala, Bipolaris, Exserohilum etc. Uncommon
Scedosporiosis
(Pseudallescheriasis)
Scedosporium and Lomentospora. Rare
Zygomycosis
(Mucormycosis)
Rhizopus, Mucor, Rhizomucor, Lichtheimia etc. Rare
5. Opportunistic Systemic Mycoses
• Aspergillosis is a spectrum of diseases of humans and animals caused by members
of the genus Aspergillus.
• These include
• 1. mycotoxicosis due to ingestion of contaminated foods;
• 2. allergy and sequelae to the presence of conidia or transient growth of the
organism in body orifices;
• 3. colonization without extension in preformed cavities and debilitated tissues;
6. Opportunistic Systemic Mycoses
• 4. invasive, inflammatory, granulomatous, narcotizing disease of lungs, and
other organs; and rarely
• 5. systemic and fatal disseminated disease.
• The type of disease and severity depends upon the physiologic state of the host and the
species of Aspergillus involved.
• The etiological agents are cosmopolitan and include Aspergillus fumigatus complex, A.
flavus complex, A. niger complex, A. nidulans and A. terreus complex.
7. Clinical manifestations…
• Pulmonary aspergillosis: including allergic, aspergilloma and invasive aspergillosis.
• The clinical manifestations of pulmonary aspergillosis are many, ranging from harmless
saprophytic colonization to acute invasive disease.
• Allergic aspergillosis is a continuum of clinical entities ranging from extrinsic asthma to extrinsic
allergic alveolitis to allergic bronchopulmonary aspergillosis (hypersensitivity pneumonitis) caused by
the inhalation of Aspergillus conidia.
• Features include asthma, intermittent or persistent pulmonary infiltrates, peripheral eosinophilia,
positive skin test to Aspergillus antigenic extracts, positive immunodiffusion precipitin tests for
antibody to Aspergillus, elevated total IgE, and elevated specific IgE against Aspergillus.
8. Clinical manifestations…
• Plug expectoration and a history of chronic bronchitis are also common.
• Symptoms may be mild and without sequelae, but recurrent episodes frequently progress
to bronchiectasis and fibrosis.
• Non-invasive aspergillosis or aspergilloma (fungus ball), is caused by the saprophytic
colonization of pre-formed cavities, usually secondary to tuberculosis or sarcoidosis.
• Features often include hemoptysis with blood stained sputum, positive immunodiffusion
precipitin tests for antibody to Aspergillus, and elevated specific IgE against Aspergillus.
• However, many cases are asymptomatic and are usually found by routine chest x-ray.
9. Acute invasive pulmonary aspergillosis.
• Predisposing factors include prolonged neutropenia, especially in leukemia
patients or in bone marrow transplant recipients, corticosteroid therapy,
cytotoxic chemotherapy and to a lesser extent patients with AIDS or chronic
granulomatous disease.
• Clinical symptoms may mimic acute bacterial pneumonia and include fever,
cough, pleuritic pain, with hemorrhagic infarction or a narcotizing
bronchopneumonia.
• The typical patient is granulocytopenia and receiving broad-spectrum antibiotics
for unexplained fever.
• Radiological features may be non-specific and tests for serum antibody precipitins
are also usually negative.
• Clinical recognition is essential as this is the most common form of aspergillosis in
the immunosuppressed patient.
10. • Chronic narcotising aspergillosis is an indolent, slowly progressive,
"semi-invasive" form of infection seen in mildly immunosuppressed
patients, especially those with a previous history of lung disease.
• Diabetes mellitus, sarcoidosis and treatment with low-dose
glucocorticoids may be other predisposing factors.
• Common symptoms include fever, cough and sputum production;
positive serum antibody precipitins may also be detected.
12. Disseminated aspergillosis:
• Hematogenous dissemination to other visceral organs may occur, especially in patients
with severe immunosuppression or intravenous drug addiction.
• Abscesses may occur in the brain (cerebral aspergillosis), kidney (renal aspergillosis),
heart, (endocarditis, myocarditis), bone (osteomyelitis), and gastrointestinal tract.
• Ocular lesions (mycotic keratitis, endophthalmitis and orbital aspergilloma) may also
occur, either as a result of dissemination or following local trauma or surgery.
• Aspergillosis of the paranasal sinuses:
• Two types of paranasal sinus aspergillosis are generally recognised. (1) A non-invasive
"aspergilloma" form, primarily seen in non-immunosuppressed individuals. Predisposing factors
include a history of chronic sinusitis and poorly draining sinuses with excessive mucus. (2) An
invasive form, usually seen in the immunosuppressed patient. This form has a similar clinical
setting to that seen in rhinocerebral zygomycosis; and symptoms include fever, rhinitis and signs of
invasion into the orbit.
• .
13. Cutaneous aspergillosis:
• Cutaneous aspergillosis is a rare manifestation that is usually a result of
dissemination from primary pulmonary infection in the immunosuppressed
patient.
• However, cases of primary cutaneous aspergillosis also occur, usually as a result
of trauma or colonisation.
• Lesions manifest as erythematous papules or macules with progressive central
necrosis
14. Laboratory diagnosis:
• Clinical material:
• Sputum, bronchial washings and tracheal aspirates from patients with pulmonary
disease and tissue biopsies from patients with disseminated disease.
• Direct microscopy:
a) Sputum, washings and aspirates make wet mounts in either 10% KOH & Parker
ink or Calcofluor and/or Gram stained smears;
b) Tissue sections should be stained with H&E, GMS and PAS digest.
• Note: Aspergillus hyphae may be missed in H&E stained sections.
• Examine specimens for dichotomously branched, septate hyphae.
17. Laboratory diagnosis…
• Interpretation:
• The presence of hyaline, branching septate hyphae, consistent with Aspergillus
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.
18. Laboratory diagnosis…
• Culture:
• Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar.
• Colonies are fast growing and may be white, yellow, yellow-brown, brown to black or green in colour.
• Interpretation:
• Aspergillus species are well recognized as common environmental airborne contaminants,
• Therefore, a positive culture from a non-sterile specimen, such as sputum, is not proof of infection.
• The detection of Aspergillus (especially A. fumigatus and A. flavus) in sputum cultures, from patients with
appropriate predisposing conditions, is likely to be of diagnostic importance and empiric antifungal therapy
should be considered.
• Unfortunately, patients with invasive pulmonary aspergillosis, often have negative sputum cultures making a
lung biopsy a prerequisite for a definitive diagnosis.
20. Laboratory diagnosis…
• Serology:
• Immunodiffusion tests for the detection of antibodies to Aspergillus species have proven to be of value in the diagnosis of
allergic, aspergilloma, and invasive aspergillosis.
• However, they should never be used alone, and must be correlated with other clinical and diagnostic data.
• Several antigen tests for the detection of Aspergillus from blood, urine and CFS are now available.
• The (1→3)- β-D- glucan test detects a wide variety of fungal pathogens including Aspergillus, Candida, Fusarium,
Trichosporon and several commercial kits (FungiTec G, Fungitell) are available.
• However the most widely used system is the Aspergillus galactomannan ELISA test (Platelia® Aspergillus ELISA kit).
• The Aspergillus galactomannan (GM) test has a reported specificity of 89-93%; sensitivity of 61-71%; NPV of 95-98%;
PPV of 26-53% (Meta-analysis 27 studies Pfeiffer et al. CID 2006).
• However as galactomannan is rapidly eliminated from blood - serial screening twice weekly for optimal diagnosis is
recommended.
22. Laboratory diagnosis…
• Identification:
• Aspergillus colonies are usually fast growing, white, yellow, yellow-brown, brown to black or
shades of green, and they mostly consist of a dense felt of erect conidiophores.
• Conidiophores terminate in a vesicle covered with either a single palisade-like layer of
phialides (uniseriate) or a layer of subtending cells (metulae) which bear small whorls of
phialides (the so-called biseriate structure).
• The vesicle, phialides, metulae (if present) and conidia form the conidial head. Conidia are
one-celled, smooth- or rough-walled, hyaline or pigmented and are basocatenate, forming long
dry chains which may be divergent (radiate) or aggregated in compact columns (columnar).
• Some species may produce Hülle cells or sclerotia.
24. Candidiasis
• Candidiasis is a primary or secondary mycotic infection caused by members of the genus Candida and other
related genera.
• The clinical manifestations may be acute, subacute or chronic to episodic.
• Involvement may be localized to the mouth, throat, skin, scalp, vagina, fingers, nails, bronchi, lungs, or the
gastrointestinal tract, or become systemic as in septicemia, endocarditis and meningitis.
• In healthy individuals, Candida infections are usually due to impaired epithelial barrier functions and occur in
all age groups, but are most common in the newborn and the elderly.
• They usually remain superficial and respond readily to treatment.
• Systemic candidiasis is usually seen in patients with cell-mediated immune deficiency, and those receiving
aggressive cancer treatment, immunosuppression, or transplantation therapy.
25. Cryptococcosis
• a chronic, subacute to acute pulmonary, systemic or meningitic disease,
• initiated by the inhalation of infectious propagules (basidiospores and/or desiccated
yeast cells) from the environment.
• Primary pulmonary infections have no diagnostic symptoms and are usually subclinical.
• On dissemination, the fungus usually shows a predilection for the central nervous system,
• However , skin, bones and other visceral organs may also become involved.
26. Cryptococcosis …
• Cryptococcus neoformans and C. gattii are the principle pathogenic species.
• Naganishia albida (formerly Cryptococcus albidus) and Patiliotrema laurentii
(formely Cryptococcus laurentii) have on occasion also been implicated in human
infection.
27. Clinical manifestations:
• Cryptococcus is an encapsulated basidiomycete yeast-like fungus with a predilection for the
respiratory and nervous system of humans and animals.
• Two species, C. neoformans and C. gattii are distinguishable biochemically and by molecular
techniques.
• In humans, C. neoformans affects immunocompromised hosts predominantly and is the
commonest cause of fungal meningitis;
• worldwide, 7-10% of patients with AIDS are affected.
• AIDS associated cryptococcosis accounts for 50% of all cryptococcal infections reported annually
and usually occurs in HIV patients when their CD4 lymphocyte count is below 200/mm3.
28. Clinical manifestations…
• Meningitis is the predominant clinical presentation with fever and headache as the most common
symptoms.
• Secondary cutaneous infections occur in up to 15% of patients with disseminated cryptococcosis
and often indicate a poor prognosis.
• Lesions usually begin as small papules that subsequently ulcerate, but may also present as
abscesses, erythematous nodules, or cellulitis.
• This variety is found worldwide.
• In contrast, the distribution of cryptococcosis due to Cryptococcus gattii is geographically
restricted, non-immunocompromised hosts are usually affected, large mass lesions in lung and/or
brain (cryptococcomas) are characteristic and morbidity from neurological disease is high.
29. Pulmonary cryptococcosis:
• Asymptomatic carriage of Cryptococcus has been reported from the respiratory tract, especially
sputum and from skin in healthy people as a result of normal environmental exposure.
• In addition, patients with chronic lung disease, such as bronchitis and bronchiectasis, may also
have asymptomatic colonization, with Cryptococcus being isolated from their sputum over many
years.
• Subclinical cryptococcosis may result of environmental exposure, normal individuals may
experience a self-limiting pneumonia with accompanying sensitization.
• Most primary infections of this type have no diagnostic symptoms and are usually discovered only
by routine chest x-ray. When present, symptoms include cough, low-grade fever and pleuritic pain.
30. Pulmonary cryptococcosis:
• Invasive pulmonary cryptococcosis may occur
• in some patients when primary infections may not readily resolve in some patients,
• leading to a more chronic pneumonia progressing slowly over several years.
• Patients may become pyrexic and have an accompanying cough, however
many pulmonary lesions are often asymptomatic, especially when chronic
granulomas are formed.
• Chronic pulmonary cryptococcosis also increases the risk of dissemination
to the central nervous system.
32. Central nervous system
• Dissemination to the brain and meninges is the most common clinical manifestation of cryptococcosis and includes
meningitis, meningoencephalitis or expanding cryptococcoma.
• Meningitis is the most common clinical form, accounting for up to 85% of the total number of cases, however the clinical
signs are rarely dramatic.
• Symptoms usually develop slowly over several months, and initially include headache, followed by drowsiness, dizziness,
irritability, confusion, nausea, vomiting, neck stiffness and focal neurological defects, such as ataxia.
• Diminishing visual acuity and coma may also occur in later stages of the infection.
• Acute onset cases may also occur, especially in patients with widespread disease, and these patients may deteriorate rapidly
and die in a matter of weeks.
• Meningoencephalitis due to invasion of the cerebral cortex, brain stem and cerebellum is an uncommon, rapid fulminate
infection, often leading to coma and death within a short time.
• Symptoms include slow response to treatment and signs of cerebral edema or hydrocephalitis, especially papilledema.
34. Cutaneous cryptococcosis:
• Primary cutaneous cryptococcosis in the form of ulcerated lesions or cellulitis
occasionally occurs, especially in immunosuppressed patients.
• These lesions may resolve spontaneously or with systemic antifungal treatment.
• However, all patients with skin lesions should be monitored carefully for possible
dissemination to the central nervous system.
• Secondary cutaneous infections occur in up to 15% of patients with disseminated
cryptococcosis and often indicate a poor prognosis.
• Lesions usually begin as small papules that subsequently ulcerate, but may also
present as abscesses, erythematous nodules, or cellulitis.
35.
36. • Cryptococcosis of bone:
• Osseous cryptococcosis occurs in up to 10% of disseminated cases and may involve bony
prominences, cranial bones and vertebrae.
• The lesions are lytic without periosteal reaction and symptoms of dull pain on movement are
reported.
• Occasional cases of arthritis have also been reported, mostly involving the knee joint.
• Ocular cryptococcosis:
• Ocular manifestations of cryptococcosis most commonly include papilledema and optic
atrophy, due to raised intracranial pressure. Other ocular signs of cryptococcosis are
uncommon and usually occur as a result of dissemination.
• Other forms of cryptococcosis:
• Cryptococcus neoformans is often isolated from urine of patients with disseminated infection.
• Occasionally, signs of pyelonephritis or prostatitis may be observed.
• Other rare forms of cryptococcosis include adrenal cortical lesions, endocarditis, hepatitis,
sinusitis, and localized oesophageal lesions.
37. • Laboratory diagnosis:
• Clinical material:
• Cerebrospinal fluid (CSF), biopsy tissue, sputum, bronchial washings, pus, blood and urine.
• Direct microscopy:
• (a) For exudates and body fluids make a thin wet film under a coverslip using India ink to demonstrate
encapsulated yeast cells. Sputum and pus may need to be digested with 10% KOH prior to India ink staining.
(b) For tissue sections use PAS digest, GMS and H&E, mucicarmine stain is also useful to demonstrate the
polysaccharide capsule. Examine for globose to ovoid, budding yeast cells surrounded by wide gelatinous
capsules. Note, non-encapsulated variants, although rare, may also occur.
• Interpretation:
• The demonstration of encapsulated yeast cells in CSF, biopsy tissue, blood or urine should be considered
significant, even in the absence of clinical symptoms. Positive sputum specimens should be considered
potentially significant, even though Cryptococcus may also occur in respiratory secretions as a saprophyte.
Basically, all patients with a positive microscopy for cryptococci, from any site should be investigated for
disseminated disease, especially by culture and antigen detection.
38.
39.
40.
41. • Culture:
• Inoculate specimens onto primary isolation media, like Sabouraud's dextrose
agar. Look for translucent, smooth gelatinous colonies, later becoming very
mucoid and cream in color.
• Interpretation:
• The isolation of C. neoformans or C. gattii from any site should be considered
significant and patients without clinical symptoms should be thoroughly
investigated for disseminated disease. Positive culture of CSF is definitive.
However, positive culture of respiratory secretions, especially in patients without
clinical symptoms, needs to be interpreted with some caution, until additional
supporting evidence is available. Isolation of Naganishia albida (Cryptococcus
albidus) or Papiliotrema laurentii (Cryptococcus laurentii), should also be
interpreted with caution as these species are infrequent pathogens and once
again, additional supporting clinical and microscopic evidence is necessary.
42. • Identification:
• The genus Cryptococcus is characterized by globose to elongate yeast-like cells or
blastoconidia that reproduce by multilateral budding. Pseudohyphae are absent
or rudimentary. On solid media the cultures are generally mucoid or slimy in
appearance. Red, orange or yellow carotenoid pigments may be produced, but
young colonies of most species are usually non-pigmented, and are cream in
color. Most strains have encapsulated cells with the extent of capsule formation
depending on the medium. Under certain conditions of growth the capsule may
contain starch-like compounds which are released into the medium by many
strains. Within the genus Cryptococcus, fermentation of sugars is negative,
assimilation of nitrate is variable and assimilation of inositol is positive. The genus
Cryptococcus is similar to the genus Rhodotorula. The distinctive difference
between the two is the assimilation of inositol, which is positive in Cryptococcus.
• Causative agents: Cryptococcus neoformans and Cryptococcus gattii.
43.
44. • Serology:
• It should be noted that the detection of cryptococcal capsular
polysaccharide antigen in spinal fluid is now the method of choice for
diagnosing patients with cryptococcal meningitis. In AIDS patients,
cryptococcal antigen can be detected in the serum in nearly 100% of
cases. However, in non-AIDS patients antigen detection in serum is
less sensitive with only about 60% of patients with cryptococcosis
reported as being positive. Note, serum specimens should be
pretreated with pronase to enhance detection of antigen and avoid
false negative results.
45.
46. Hyalohyphomycosis
• A mycotic infection of man or animals caused by a number of hyaline (non-dematiaceous) hyphomycetes where the tissue morphology of the causative organism is mycelial. This separates it from phaeohyphomycosis
where the causative agents are brown-pigmented fungi. Hyalohyphomycosis is a general term used to group together infections caused by unusual hyaline fungal pathogens that are not agents of otherwise-named
infections; such as Aspergillosis. Etiological agents include species of Penicillium, Paecilomyces, Acremonium, Beauveria, Fusarium and Scopulariopsis.
• Clinical manifestations:
• The clinical manifestations of hyalohyphomycosis are many ranging from harmless saprophytic colonization to acute invasive disease. Predisposing factors include prolonged neutropenia, especially in leukemia
patients or in bone marrow transplant recipients, corticosteroid therapy, cytotoxic chemotherapy and to a lesser extent patients with AIDS. The typical patient is granulocytopenic and receiving broad-spectrum
antibiotics for unexplained fever.
• Laboratory diagnosis:
• Clinical material:
• Skin and nail scrapings; urine, sputum and bronchial washings; cerebrospinal fluid, pleural fluid and blood; tissue biopsies from various visceral organs and indwelling catheter tips.
• Direct microscopy:
• (a) Skin and nail scrapings, sputum, 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 PAS digest, Grocott's methenamine silver (GMS) or Gram stains. Note hyphal elements are often
difficult to detect in H&E stained sections.
• Interpretation: The presence of hyaline, branching septate hyphae, similar to Aspergillus 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.
47. • Culture:
• Clinical specimens should be inoculated onto primary isolation media, like
Sabouraud's dextrose agar.
• Interpretation:
• The hyaline 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.
48. Culture of Chrysosporium [left] and Fusarium [right] showing
typical colony colour for a hyaline hyphomycete ie any colour
except brown, olivaceous black or black.
49. • Serology:
• There are currently no commercially available serological procedures for the
diagnosis of any of the infections classified under the term hyalohyphomycosis.
• 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.
• Causative agents:
• Acremonium sp., Beauveria sp., Fusarium sp., Paecilomyces sp., Penicillium sp.,
Scopulariopsis sp. etc.
50. 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 especially
species of Exophiala, Phialophora, Bipolaris, Exserohilum,
Cladophialophora, Verruconis, Aureobasidium, Cladosporium,
Curvularia and Alternaria. Ajello (1986) listed 71 species from 39
genera as causative agents of phaeohyphomycosis.
51. Scedosporosis (Pseudallesheriasis)
• Scedosporium and Lomentospora infection
• A spectrum of disease similar in terms of variety and severity to those caused by Aspergillus. The vast majority of infections are
mycetomas, the remainder include infections of the eye, ear, central nervous system, internal organs and more commonly the
lungs. Infections result from either inhalation of air-borne conidia or by the traumatic implantation of fungal elements due to a
penetrating injury. The etiological agents are Scedosporium apiospermum,Scedosporium aurantiacum, Scedosporium boydii and
Lomentospora prolificans.
• Clinical manifestations:
• Scedosporium apiospermum, Scedosporium boydii and Scedosporium aurantiacum infections:
• Non-invasive colonization of the external ear and pulmonary colonization in patients with poorly draining bronchi or paranasal
sinuses and "fungus ball" formation in pre-formed cavities are similar to those seen in Aspergillus.
• Invasive infections in normal patients are usually caused by traumatic implantation. Mycetoma, where the fungus exists in tissue
as resistant microcolonies or grains is the most common infection in the normal patient. This is followed by penetrating joint
injuries, especially to the knee, resulting in arthritis and osteomyelitis. Other manifestations include mycotic keratitis and non-
mycetoma like cutaneous and subcutaneous infections.
• Invasive infections have also been reported in patients receiving treatment with corticosteroids and immunosuppressive therapy
for organ transplantation, leukemia, lymphoma, systemic lupus erythematous or Crohn's disease. Infections include invasive
sinusitis, pneumonia, arthritis with osteomyelitis, cutaneous and subcutaneous granulomata, meningitis, brain abscesses,
endophthalmitis, and disseminated systemic disease.
52. • Lomentospora prolificans infections:
• The spectrum of clinical manifestations are similar to that described above
for Scedosporium. Disseminated disease has been reported in
immunosuppressed patients especially those with prolonged neutropenia
and post-transplantation therapy. Colonization of the external ear,
paranasal sinuses and lung, including "fungus ball" have been reported.
Cases of onychomycosis and mycotic keratitis have also been documented.
However, localized invasive infections, especially septic arthritis and
osteomyelitis following penetrating injuries to joints, are now an emerging
clinical problem, accounting for 80% of the reported cases. Culture
identification is important, because this fungus is often resistant to
antifungal therapy and treatment may require surgical intervention.
53. Laboratory diagnosis:
• Clinical material:
• Sputum, bronchial washings and tracheal aspirates from patients with pulmonary disease and tissue biopsies from patients with subcutaneous and disseminated disease.
• Direct microscopy:
• (a) Sputum, washings and aspirates make wet mounts in either 10% KOH & Parker ink or Calcofluor and/or Gram stained smears; (b) Tissue sections should be stained with H&E,
GMS and PAS digest. Note hyphal elements of Scedosporium species and Lomentospora prolificans are indistinguishable from those of Aspergillus hyphae and may be missed in
H&E stained sections. Examine specimens for branched, septate hyphae.
• Interpretation:
• The presence of 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 culture is necessary for a specific identification of the causative agent.
• Culture:
• Colonies are fast growing and are greyish-white, to olive-grey to black with a suede-like to downy surface texture.
• Interpretation:
• S. apiospermum, S. boydii, S. aurantiacum and L. prolificans are common soil fungi, 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 positive culture from a biopsy or aspirated material from a sterile site should be considered
significant. Culture identification is the only reliable means of distinguishing these fungi from Aspergillus species.
54. • Serology:
• As in cases of aspergillosis immunodiffusion tests have become valuable in the
diagnosis of pseudallescheriasis. However, at present reagents are not
commercially available and antigenic extracts have to be made in the laboratory.
• 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, in this case an annellide.
• Causative agents:
• Scedosporium apiospermum, Scedosporiun aurantiacum, Scedosporium boydii,
Lomentospora prolificans.
55. Zygomycosis(Mucormycosis)
• 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 although
infections in humans and animals are generally rare. Medically
important genera causing systemic zygomycosis (Mucormycosis)
Rhizopus, Lichtheimia, Rhizomucor, Mucor, Cunninghamella,
Saksenaea, Apophysomyces, Cokeromyces and Mortierella.
57. • Histopathology: Haematoxylin and eosin (H&E) stained section of tissue
showing broad septate hyphae surrounded by an eosinophilic sheath
(Splendore-Hoeppli phenomenon) typical of Entomophthoromycosis. Note
there are two major histological differences between subcutaneous
zygomycosis caused by Basidiobolus and Conidiobolus
(Entomophthoromycosis) and zygomycosis caused by members of the
Mucorales (mucormycosis). Firstly, in Entomophthoromycosis the hyphae
are surrounded by an eosinophilic sheath and there is a lack of vascular
invasion, which is so characteristic of infections caused by the Mucorales.
Secondly, the hyphal elements of Mucorales are sparsely septate in tissue,
whereas frequent septation is seen in tissue hyphae of Basidiobolus or
Conidiobolus.
58.
59. • Culture: Basidiobolus ranarum on Sabouraud's dextrose agar after 17
days incubation at 26C showing a flat, yellowish-grey, glabrous,
radially folded colony covered by a fine, powdery, white surface
mycelium.
• Note the satellite colonies formed by germinating conidia ejected
from the primary colony.
60.
61. • Microscopy: Microscopic morphology of Basidiobolus ranarum showing globose, one-
celled conidia that are forcibly discharged from a sporophore.
• The sporophore has a distinct swollen area just below the spore that actively participates
in the discharge of the spore.
• Comments: Basidiobolus ranarum is commonly present in decaying fruit and vegetable
matter, and as a commensal in the intestinal tract of frogs, toads and lizards. It has been
reported from tropical regions of Africa and Asia including India, Indonesia and Australia.
