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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 parallelled 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.

Disease Causative organisms  Incidence
Candidiasis  Candida, Debaryomyces, Kluyveromyces, Meyerozyma, Pichia, etc. Common
Cryptococcosis Cryptococcus spp. especially C. neoformans/C. gattii Rare/Common
Aspergillosis Aspergillus fumigatus complex, A. flavus, complex,
A. terreus complex etc.
Rare
Scedosporiosis
(Pseudallescheriasis)
Scedosporium and Lomentospora. Rare
Zygomycosis
(Mucormycosis)
Rhizopus, Mucor, Rhizomucor,
Lichtheimia etc.
Rare
Hyalohyphomycosis   Penicillium, Paecilomyces,
Beauveria, Fusarium, 
Scopulariopsis etc.
Rare
Phaeohyphomycosis  Cladophialophora, Exophiala, Bipolaris, Exserohilum etc. Rare

Mycoses Descriptions

  • 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.

    Clinical manifestations:

    1. Oropharyngeal candidiasis: including thrush, glossitis, stomatitis and angular cheilitis.

    Acute oral candidiasis is rarely seen in healthy adults but may occur in up to 5% of newborn infants and 10% of the elderly. However, it is often associated with severe immunological impairment due to diabetes mellitus, leukemia, lymphoma, malignancy, neutropenia and HIV infection where it presents as a predictor of clinical progression to AIDS. The use of broad-spectrum antibiotics, corticosteroids, cytotoxic drugs, and radiation therapy are also predisposing factors. Clinically, white plaques that resemble milk curd form on the buccal mucosa and less commonly on the tongue, gums, the palate or the pharynx. Symptoms may be absent or include burning or dryness of the mouth, loss of taste, and pain on swallowing.

    2. Cutaneous candidiasis: including intertrigo, diaper candidiasis, paronychia and onychomycosis.

    Intertriginous candidiasis is most commonly seen in the axillae, groin, inter- and sub-mammary folds, intergluteal folds, interdigital spaces, and umbilicus. Moisture, heat, friction and maceration of the skin are the principle predisposing factors in the normal patient, however obesity, diabetes mellitus, warm water immersion or occlusion of the skin and the use of broad-spectrum antibiotics are additional factors. Lesions consist of a moist, macular erythematous rash with typical satellite lesions present on the surrounding healthy skin.

    Diaper candidiasis is common in infants under unhygienic conditions of chronic moisture and local skin maceration associated with ammonitic irritation due to irregularly changed unclean diapers. Once again characteristic erythematous lesions with erosions and satellite pustules are produced, with prominent involvement of the skin folds and creases.

    Paronychia of the finger nails may develop in persons whose hands are subject to continuous wetting, especially with sugar solutions or contact with flour, that macerates the nail folds and cuticle. Lesions are characterized by the development of a painful, erythematous swelling about the affected nails. In chronic cases the infection may progress to cause onychomycosis with total detachment of the cuticle from the nail plate.

    Chronic Candida onychomycosis often causes complete destruction of nail tissue and is seen in patients with chronic mucocutaneous candidiasis or other underlying factors that affect either the hormonal or immunologic status of the host. These include diabetes mellitus, hypoparathyroidism, Addison's disease, dysfunction of the thyroid, malnutrition, malabsorption and various malignancies. The use of steroids, antibiotics and antimitotics may also be contributing factors.

    3. Vulvovaginal candidiasis and balanitis:

    Vulvovaginal candidiasis is a common condition in women, often associated with the use of broad-spectrum antibiotics, the third trimester of pregnancy, low vaginal pH and diabetes mellitus. Sexual activity and oral contraception may also be contributing factors and infections may extend to include the perineum, the vulva and the entire inguinal area. Chronic refractory vaginal candidiasis, associated with oral candidiasis, may also be a presentation of HIV infection or AIDS. Symptoms include intense vulval pruritus, burning, erythema and dyspareunia associated with a creamy white, curd-like discharge.

    In cases of balanitis, diabetes mellitus should be excluded and the sexual partner should be investigated for vulvovaginitis. The symptoms include erythema, pruritus and vesiculopustules on the glan penis or prepuce. Infections are more commonly seen in uncircumcised men and poor hygiene may also be a contributing factor.

    4. Chronic mucocutaneous candidiasis:

    Chronic mucocutaneous candidiasis is a form of persistent candidiasis, usually caused by C. albicans, of the skin, nails and mucous membranes that occurs in patients with various metabolic disturbances to cell-mediated immunity. These include defects in leukocyte function or endocrine disorders such as hypoparathyroidism, Addison's disease, hypothyroidism, diabetes, dysfunction of the thyroid and polyglandular autoimmune disease. The patients are usually children. Candida granuloma is a severe localized form which may occur with or without endocinopathy characterized by marked hyperkeratic granulomatous lesions.

    5. Neonatal and congenital candidiasis:

    Low birthweight and age, prolonged intravascular catheterization and the use of antibiotic drugs are the principle predisposing conditions for systemic candidiasis in neonates. Blood cultures are often positive and there is also a high incidence of meningitis. Renal complications due to fungus ball formation in the ureters or renal pelvis may also occur. Congenital candidiasis acquired in utero is usually confined to the skin in the form of a generalized erythematous vesicular rash, however intrauterine candidiasis may also result in abortion.

    6. Oesophageal candidiasis:

    Oesophageal candidiasis is frequently associated with AIDS and severe immunosuppression following treatment for leukemia or solid tumors. Concomitant oral candidiasis is often present. Oesophagitis may also lead to septicemia and disseminated candidiasis. Symptoms include burning pain in the substernal area, dysphagia, nausea and vomiting. The clinical diagnosis relies on radiological and endoscopic findings, which usually shows white mucosal plaques with erythema resembling those seen in oral candidiasis. Herpes simplex or cytomegalovirus (CMV) infection may also be present and the clinical diagnosis may need to be confirmed by histopathology and culture.

    7. Gastrointestinal candidiasis:

    Patients with acute leukemia or other hematological malignancies may have numerous ulcerations of the stomach and less commonly the duodenum and intestine. Perforation can lead to peritonitis and hematogenous spread to the liver, spleen and other organs. Colonization and invasion of the stomach or intestinal mucosa is often accompanied by the excretion of large numbers of yeasts which may be detected in stools.

    8. Pulmonary candidiasis:

    Pulmonary candidiasis can be acquired by either hematogenous dissemination causing a diffuse pneumonia or by bronchial extension in patients with oropharyngeal candidiasis. Aspiration of yeasts from the oral cavity has also been reported in infants. Pulmonary candidiasis is difficult to diagnose due to non-specific radiological and culture findings and most patients, especially those with granulocytopenia, present at autopsy. The presence of yeasts in alveolar lavage or sputum specimens is not specific and blood cultures may also be negative. Unfortunately, only histopathology can provide a definitive diagnosis and this is not always possible in patients with coagulation problems.

    9. Peritonitis:

    Candida peritonitis can result from colonization of indwelling catheters used for peritoneal dialysis (CAPD) or gastrointestinal perforation due to ulcers, diverticular colitis, surgery or intra-abdominal neoplasm. Symptoms include fever, abdominal pain, tenderness and a cloudy peritoneal dialysate containing greater than 100 leukocytes/mm3Candida peritonitis usually remains localized to the abdominal cavity unless patients are severely immunosuppressed.

    10. Urinary tract candidiasis:

    Transient asymptomatic candiduria may occur during antibiotic or corticosteroid treatment which promotes the growth of Candida, throughout the gastrointestinal and genital tracts, and most lower urinary tract infections result from local spread of yeasts from these sites. This condition is most common in women. Candida cystitis or bladder colonization may be caused by prolonged catheterization with concomitant antibiotic treatment, diabetes and glycosuria, anatomical uropathy, previous bladder endoscopy or surgery, diabetic neurogenic bladder, chronic outlet obstruction from prostatic hypertrophy, or pelvic irradiation for cervical cancer.

    Renal candidiasis (pyelonephritis) is usually the result of either an ascending infection or more frequently, hematogenous dissemination from another organ focus. Symptoms include fever, rigors, lumbar pain and abdominal pain. The development of a fungus ball in the renal pelvis, although rare may complicate the infection. Predisposing factors for this include constriction of the urinary tract, localized papillary necrosis, urethral or bladder catheters and diabetes. Even though, up to 80% of patients with disseminated candidiasis also have renal infection and associated candiduria, urine cultures alone are not a reliable method for diagnosis of disseminated infection.

    The practical problem in a patient with candiduria is to distinguish between colonization and/or contamination and infection. Therefore, it is important to determine whether renal function is present or whether infection is confined to the bladder. Mycological findings are usually inconclusive which makes the clinical parameters important. The following criteria are suggestive of renal infection; the isolation of yeasts in urine specimens obtained by suprapubic aspiration, positive blood cultures and a positive immunodiffusion precipitin test result or serological conversion in a patient with iatrogenic predisposing factors and/or an underlying illness.

    It should be noted that many clinicians do not recommend suprapubic aspirates as they are invasive and require additional expertise, especially in immunocompromised patients. Laboratories are also advised on the need to report the isolation of any yeasts from urine specimens obtained from high risk immunosuppressed patients.

    11. Meningitis:

    Candida meningitis is a rare entity, predominantly seen in low birthweight neonates with septicemia and in patients with hematological malignancies, complicated neurosurgery or intracerebral prosthetic devices such as ventriculoperitoneal shunts. Symptoms include a feverish meningeal irritation. Diagnosis in the neonate requires a high index of suspicion by the clinician to the possibility of meningitis as a sequel to septicemia. The detection of Candida cells in smears and its isolation from CSF is often difficult.

    12. Hepatic and hepatosplenic candidiasis:

    Hepatosplenic candidiasis occurs in patients with severe neutropenia, usually acute leukemia. Symptoms include fever, hepatosplenomegaly and increased blood concentrations of alkaline phosphatases. Histopathology shows diffuse hepatic and/or splenic necrotic lesions or abscesses containing small numbers of pseudohyphae. However, blood and biopsy cultures are usually culture negative. A definitive diagnosis is often difficult due to the inability to adequately biopsy these patients.

    13. Endocarditis, myocarditis and pericarditis:

    Endocarditis is the most common form of cardiac candidiasis. Pre-existing valvular disease with concomitant intravenous catheterization and antibiotic treatment, intravenous drug abuse, heart surgery and valve prosthesis are the most common predisposing factors. Clinical symptoms include fever, murmur, congestive heart failure, anemia and splenomegaly. Blood cultures are often positive and echocardiology and serology for the detection of Candida antibodies (immunodiffusion precipitin tests) are other useful diagnostic procedures. Myocardial abscesses, arterial emboli and purulent pericarditis are additional rare complications of Candida septicemia or surgery.

    14. Candidemia (Candida septicemia) and disseminated candidiasis:

    Candidemia has been defined as the presence of yeasts in the blood with or without visceral involvement. Hematogenous dissemination may then occur to one or more other organ systems with the formation of numerous microabscesses. Candida species have been reported to cause up to 15% of cases of septicemia seen in hospital patients.

    Predisposing factors include intravenous catheters, use of antibacterial drugs, urinary catheters, surgical procedures, corticosteroid therapy, neutropenia, severe burns, parental nutrition, and chemotherapy induced impairment of oropharyngeal or gastrointestinal mucosa. A characteristic presentation is antibiotic resistant fevers in the neutropenic patient with tachycardia and dyspnea. Hypotension is also common and skin lesions may also occur.

    When yeasts are isolated from blood or from tissue biopsies a diagnosis is straightforward, however this is not often the case. Blood cultures often remain negative even in patients dying from proven disseminated candidiasis, especially in the granulocytopenic patient. If at all possible, suspected foci should be aspirated, including articular, peritoneal, CSF, or even vitreal specimens; and liver and/or lung biopsies should also be performed. However histopathology is more often not a viable option because biopsies are contraindicated due to the patients underlying illness. Finally, the detection of yeasts from more accessible no-sterile sites, like urine, is too common to be of diagnostic value. In this situation, of clinically suspected unproven disseminated candidiasis, only cutaneous and/or ocular lesions can rapidly confirm the diagnosis. Specific, reliable serological tests are still not generally available. Empiric antifungal treatment is usually initiated in these cases.

    15. Ocular candidiasis:

    Candida endophthalmitis is often associated with candidemia, indwelling catheters or drug abuse, however it is rare in patients with severe neutropenia. Lesions are often localized near the macula and patients complain of cloudy vision. Exogenous Candida endophthalmitis is rare, but cases have been reported following ocular trauma or surgery. Similarly, conjunctival and corneal infections have also been recorded following trauma.

    16. Osteoarticular candidiasis:

    Arthritis may be a late sequel of candidemia in neonates or neutropenic patients. Prosthetic or rheumatoid joints are also prone to infection by Candida either by hematogenous spread or direct inoculation during surgery or intra-articular corticosteroid injection. The knee is the main site involved with pain on weight bearing or on full extension. The diagnosis depends on the isolation of yeasts from joint fluid obtained by needle aspiration or from synovial biopsies.

    17. Other forms of candidiasis:

    As candidiasis is an iatrogenic, nosocomial infection which is usually endogenous in origin many other clinical manifestations may occur, especially in the debilitated patient. For example, the reported cutaneous, ocular and arthritic manifestations reported in heroin addicts; fever, rash and myalgia associated with leukemia patients; Candida cholecystitis; Candida prostatitis; pancreatic abscesses; epiglottitis and osteomyelitis, to name a few.

    Summary of clinical groups and/or predisposing factors for invasive candidiasis.

    Neutropenia (especially >7 days).
    Hematological malignancy.
    Solid tumor malignancy.
    Postsurgical intensive care patients.
    Prolonged intravenous catheterization.
    Broad-spectrum or multiple antibiotic therapy.
    Diabetes mellitis.
    Parental nutrition.
    Severe burns.
    Neonates.
    Corticosteroid therapy.
    Intravenous drug abuse.

    Laboratory diagnosis:

    1. 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.

    2. Direct Microscopy: 
    (a) Skin and nails 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 and/or gram stained smears; (c) Tissue sections should be stained using PAS digest, Grocott's methenamine silver (GMS) or Gram stain. Note Candida may be missed in H&E stained sections. Examine specimens for the presence of small, round to oval, thin-walled, clusters of budding yeast cells (blastoconidia) and branching pseudohyphae. Candida pseudohyphae may be difficult to distinguish from Aspergillus hyphae when blastoconidia are not observed as often happens in liver biopsies.

    Interpretation: 
    As a rule, a positive direct microscopy from a sterile site, especially a tissue biopsy, should be considered significant, even if the laboratory is unable to culture the yeast. Further, the demonstration of pseudohyphae in scrapings or smears from cutaneous, oral, esophageal and vaginal lesions should be considered significant, provided the clinical manifestations support the diagnosis. However, the finding of just budding yeast cells in such material is of little diagnostic importance. Note, pseudohyphae will not be observed in smears when C. glabrata is involved and the diagnosis will require additional supporting evidence. Direct microscopy of sterile body fluids, such as CSF, vitreous humor, joint fluid and peritoneal fluid is relatively insensitive and positive culture will usually be required to make a diagnosis.

    3. Culture:
     
    Colonies are typically white to cream colored with a smooth, glabrous to waxy surface.

    Interpretation: 
    A positive culture from blood, or other sterile body fluid, or tissue biopsy should be considered significant. Lysis centrifugation is currently the most sensitive method for the isolation of Candida from blood. However, positive culture from non-sterile specimens such as sputum, bronchial lavage, esophageal brushings, urine, stool, and surgical drains are of little diagnostic value. Similarly, culture of skin or mucous membrane lesions without supporting evidence from direct microscopy is not diagnostic. Candida species are commonly isolated from the mouth, vagina, anus, and less often, moist skin surfaces of normal individuals who do not have candidiasis.

    4. Serology: 
    Various serological procedures have been devised to detect the presence of Candida antibodies, ranging from immunodiffusion to more sensitive tests such as counter immunoelectrophoresis (CIE), enzyme-linked immunosorbent assay (ELISA), and radioimmunoassay (RIA). However, these are often negative in the immunocompromised patient, especially at the beginning of an infection. The production of four or more precipitin lines in CIE tests has been reported to be diagnostic of candidiasis in the predisposed patient .

    Tests for circulating antigen by immunological or non-immunological means have also been developed. Of the non-immunological techniques, use of gas liquid chromography (GLC) to detect mannose derivatives of the cell wall or a metabolic by-product, D-arabinitol, have proved the most useful. The detection of antigen by immunological methods such as ELISA or RIA have been used, however for the small laboratory latex agglutination tests for glycoprotien antigen have proved to be the most useful, although variable results have been reported.

    It must be stressed that the interpretation of serological tests for Candida, especially in the neutropenic patient, is often difficult and must be correlated with other diagnostic methods. False-negatives and false-positive results do occur. Hopwood and Evans (1991) provide an excellent review of the current serological methods available.

    5. Identification: 
    The genus Candida is characterized by globose to elongate yeast-like cells or blastoconidia that reproduce by multilateral budding. Most Candida species are also characterized by the presence of well developed pseudohyphae, however this characteristic may be absent, especially in those species formally included in the genus Torulopsis. Arthroconidia, ballistoconidia and colony pigmentation are always absent. Within the genus Candida, fermentation, nitrate assimilation and inositol assimilation may be present or absent, however, all inositol positive strains produce pseudohyphae.

    Causative agents:

    Candida albicans 
    Candida catenulata 
    Candida dubliniensis 
    Candida glabrata complex
    Candida haemulonii 
    Candida inconspicua 
    Candida parapsilosis complex
    Candida rugosa 
    Candida tropicalis
    Clavispora lusitaniae (formerly Candida lusitaniae) 
    Cyberlindnera fabianii (formerly Candida fabianii) 
    Debaryomyces hansenii (formerly Candida famata) 
    Kluyveromyces marxianus (formerly Candida kefyr)
    Meyerozyma guilliermondii (formerly Candida guilliermondii)
    Pichia kudriavzevii (formerly Candida krusei) 
    Pichia norvegensis (formerly Candida norvegensis) 
    Torulaspora delbrueckii (formerly Candida colliculosa) 
    Wickerhamomyces anomalus (formerly Candida pelliculosa) 
    Yarrowia lipolytica (formerly Candida lipolytica)

    Management: see treatment guidelines section.

    AmFurther reading:
    Ajello L and R.J. Hay. 1997. Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections. 9th Edition, Arnold London.
    Barnett et al. 1990. Yeasts characteristics and identification. Cambridge University Press, New York. Computerised identification key also available.
    Chandler FW., W. Kaplan and L. Ajello. 1980. A colour atlas and textbook of the histopathology of mycotic diseases. Wolfe Medical Publications Ltd. London.
    Elewski BE. 1992. Cutaneous fungal infections. Topics in dermatology. Igaku-Shoin, New York and Tokyo.
    Ellis, D.H., D, Marriott and T. Sorrell. Candidial and Cryptococcal infections. An interactive CD-ROM, Pfizer Australia.
    Kreger-van Rij. 1996. [4th edition due out any time] The yeasts a taxonomic study. Elsevier Science Publishes B.V. Amsterdam.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Odds, F.C. 1988. Candida and candidosis. 2nd Ed. Bailliere Tindall, London.
    Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.
    Warnock DW and MD Richardson. 1991. Fungal infection in the compromised patient. 2nd edition. John Wiley & Sons

  • Cryptococcosis

    Cryptococcosis is 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. Although C. neoformans and C. gattii are regarded as the principle pathogenic species, Cryptococcus albidus and C. laurentii have on occasion also been implicated in human infection.

    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. 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. Human disease is endemic in Australia, Papua New Guinea, parts of Africa, the Mediterranean region, India, south-east Asia, Mexico, Brazil, Paraguay and Southern California.

    1. 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.

    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.


    2. 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.

    Cryptococcoma is a rare entity, characterized by localized, solid, tumor-like masses, usually found in the cerebral hemispheres or cerebellum, or more rarely in the spinal cord. Symptoms are consistent with an expanding intracranial mass and include headache, drowsiness, nausea, vomiting, mental changes, slurred speech, double vision, unsteadiness of gait, coma, paralysis and hemiparesis. These symptoms may mimic cerebral neoplasm which may delay a true diagnosis.


    3. 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.

    In patients with AIDS, skin manifestations represent the second most common site of disseminated cryptococcosis. Lesions often occur on the head and neck and may present as papules, nodules, plaques, ulcers, abscesses, cutaneous ulcerated plaques, herpetiform lesions, lesions simulating both molluscum contagiosum and Kaposi's sarcoma. Anal ulceration may also occur.

    4. 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.

    5. 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.

    6. 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.

    Laboratory Diagnosis:

    1. Clinical material: 
    Cerebrospinal fluid (CSF), biopsy tissue, sputum, bronchial washings, pus, blood and urine.

    2. 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.

    3. 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 Cryptococcus albidus or C. laurentii, should also be interpreted with caution as these species are infrequent pathogens and once again, additional supporting clinical and microscopic evidence is necessary.

    4. 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.

    5. 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.

    6. Causative agents:
    Cryptococcus albidus, Cryptococcus laurentii, Cryptococcus neoformans, Cryptococcus gattii.
     
    Further reading:
    Ajello L and R.J. Hay. 1997. Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections. 9th Edition, Arnold London.
    Ellis, D.H. and T.J. Pfeiffer. 1992. The ecology of Cryptococcus neoformans. Eur. J. Epidemiol. 8:3
    Ellis, D.H., D, Marriott and T. Sorrell. Candidial and Cryptococcal infections. An interactive CD-ROM , Pfizer Australia.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.
    Warnock DW and MD Richardson. 1991. Fungal infection in the compromised patient. 2nd edition. John Wiley & Sons.

  • Aspergillosis

    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) colonisation without extension in preformed cavities and debilitated tissues; (4) invasive, inflammatory, granulomatous, narcotising 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.

    Clinical Manifestations:

    1. Pulmonary Aspergillosis: including allergic, aspergilloma and invasive aspergillosis.
    The clinical manifestations of pulmonary aspergillosis are many, ranging from harmless saprophytic colonisation 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. 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 colonisation 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 roentenogram.

    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 narcotising bronchopneumonia. The typical patient is granulocytopenic 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.

    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.

    2. 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.

    3. 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.

    4. 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.

    Laboratory Diagnosis:

    1. Clinical material: 
    Sputum, bronchial washings and tracheal aspirates from patients with pulmonary disease and tissue biopsies from patients with disseminated disease.

    2. 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.

    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.

    3. 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 recognised as common environmental airborne contaminants, therefore a positive culture from a non-sterile specimen, such as sputum, is not proof of infection. However, 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.

    4. 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.


    5. 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.

    6. Causative agents:
    Aspergillus spp. Aspergillus flavus complex, Aspergillus fumigatus complex, Aspergillus nidulans complex, Aspergillus niger complex, Aspergillus terreux complex.

    Further reading:
    Chandler FW., W. Kaplan and L. Ajello. 1980. A colour atlas and textbook of the histopathology of mycotic diseases. Wolfe Medical Publications Ltd. London.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.
    Warnock DW and MD Richardson. 1991. Fungal infection in the compromised patient. 2nd edition. John Wiley & Sons.

  • Scedosporiosis (Pseudallescheriasis)

    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:

    1. 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.

    2. 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.

    Laboratory Diagnosis:

    1. Clinical material: 
    Sputum, bronchial washings and tracheal aspirates from patients with pulmonary disease and tissue biopsies from patients with subcutaneous and disseminated disease.

    2. 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 boydii and Scedosporium 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.

    3. 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.

    4. 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.

    5. 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.

    6. Causative agents:
    Scedosporium apiospermum, Scedosporiun aurantiacum, Scedosporium boydii, Lomentospora prolificans.

    Further reading:
    Ajello L and R.J. Hay. 1997. Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections. 9th Edition, Arnold London.
    Gilgado, F., J. Cano, J. Gene and J. Guarro. 2005. Molecular phylogeny of the Pseudallescheria boydii species complex: proposal of two new species.   J. Clin. Microbiol. 43:4930-4942.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.
    Warnock DW and MD Richardson. 1991. Fungal infection in the compromised patient. 2nd edition. John Wiley & Sons.

  • 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 orders and genera include:

    1. Mucorales and Mortierellales, causing subcutaneous and systemic zygomycosis (Mucormycosis) - Rhizopus, Lichtheimia, Rhizomucor, Mucor, Cunninghamella, Saksenaea, Apophysomyces, Cokeromyces and Mortierella.

    2. Entomophthorales, causing subcutaneous zygomycosis (Entomophthoromycosis) - Conidiobolus and Basidiobolus.

    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, intravenous drug abuse, and other diseases such as 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. 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.


    1. 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.

    2. Pulmonary zygomycosis:
    Predisposing conditions include haematological malignancies, lymphoma and leukemia, or severe neutropenia, treatment with cytotoxins and corticosteroids, desferrioxamine therapy; diabetes and organ transplantation. Infections result by inhalation of sporangiospores into the bronchioles and alveoli, leading to pulmonary infraction and necrosis with cavitation.

    3. 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.

    4. 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.

    5. Disseminated zygomycosis: 
    May originate from any of the above, especially in severely debilitated patients with haematological malignancies, burns, diabetes or uraemia.

    6. Central Nervous System alone: 
    Intravenous drug abuse. Traumatic implantation leading to brain abscess.

    Laboratory Diagnosis:

    1. 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.

    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.

    2. Direct Microscopy:
    (a) Scrapings, sputum and exudates should be examined using 10% KOH & Parker ink or Calcofluor mounts; and (b) 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.

    Interpretation:
    As a rule, a positive direct microscopy, especially from a sterile site, should be considered significant, even if the laboratory is unable to culture the fungus.

    3. 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 recognised 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. Obviously, 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.

    4. Serology: 
    There are currently no commercially available serological procedures for the diagnosis of zygomycosis. Although some laboratories have developed ELISA tests for the detection of antibodies to Zygomycetes.

    5. Identification: 
    Zygomycetes are usually fast growing fungi characterised 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.

    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 (25,37,45C) 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 mould's failure to sporulate on the primary isolation media or on subsequent subculture onto potato dextrose agar. Sporulation may be stimulated by the use of nutrient deficient media, like cornmeal-glucose-sucrose-yeast extract agar, Czapek Dox agar, or by using the agar block method on water agar.

    6. Causative agents:
    Lichtheimia corymbifera, Apophysomyces elegans, Cunninghamella bertholletiae, Mortierella wolfii, Mucor sp., Rhizomucor pusillus, Rhizopus arrhizus, Rhizopus sp., Saksenaea vasiformis.

    Further reading:
    Ellis, DH.  2005.  Systemic Zygomycetes – Mucormycosis.  Chapter 33. In Topley and Wilson’s Microbiology and Microbial Infections: Medical Mycology, 10th edition, Hodder Arnold London. pp 659-686.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.

    Infections caused by entomophthoraceous fungi:

    Zygomycosis due to entomophthoraceous fungi:
    This is caused by species of two genera Basidiobolus and Conidiobolus. Infections are chronic, slowly progressive and generally restricted to the subcutaneous tissue in otherwise healthy individuals. Other characteristics that separate these infections from those caused by mucoraceous fungi are a lack of vascular invasion or infarction and the production of a prolific chronic inflammatory response, often with eosinophils and Splendore-Hoeppli phenomena around the hyphae.

    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.

    Zygomycosis caused by Conidiobolus sp.:
    This is a chronic inflammatory or granulomatous disease that is typically restricted to the nasal submucosa and characterised 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. Symptoms include nasal obstruction, drainage and sinus pain. Subcutaneous nodules develop in the nasal and perinasal regions and progressive generalised facial swelling may occur. Infections also occur in horses usually producing extensive nasal polyps and other animals. Conidiobolus coronatus is also a recognised pathogen of termites, other insects and spiders.

    Laboratory Diagnosis:

    1. Clinical Material: 
    Skin biopsy tissue.

    2. 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.

    Further reading:
    Ellis, DH.  2005.  Subcutaneous Zygomycetes – Subcutaneous zygomycosis.  Chapter 17. In Topley and Wilson’s Microbiology and Microbial Infections: Medical Mycology, 10th edition, Hodder Arnold London pp 347-355.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.

  • 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:

    1. 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.

    2. 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.

    3. 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.

    4. Serology: 
    There are currently no commercially available serological procedures for the diagnosis of any of the infections classified under the term hyalohyphomycosis.

    5. 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.

    6. Causative agents:
    Acremonium sp., Beauveria sp., Fusarium sp., Paecilomyces sp., Penicillium sp., Scopulariopsis sp. etc.

    Further reading:
    Ajello L and R.J. Hay. 1997. Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections. 9th Edition, Arnold London.
    Booth, C. 1977. Fusarium: laboratory guide to the identification of the major species. Commonwealth Mycological Institute, Kew, Surrey, England.
    Burgess, L.W., and C.M. Liddell. 1983. Laboratory manual for Fusarium research. Fusarium Research Laboratory, Department of Plant Pathology and Agricultural Entomology. The University of Sydney, Australia.
    Domsch, Gams and Anderson. 1980. Compendium of soil fungi Volume 1. Academic Press.
    Hoog de GS and J Guarro. 1994. Atlas of Clinical Fungi from Centraalbureau voor Schimmelcultures, Baarn, The Netherlands. CBS publications may be ordered from Tinke van den-Berg-Visser, Centraalbureau voor Schimmelcultures, PO Box 273, 3740 AG Baarn, The Netherlands FAX + 31 2154 16142.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
    Warnock DW and MD Richardson. 1991. Fungal infection in the compromised patient. 2nd edition. John Wiley & Sons.

  • 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.

    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.

    1. 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 and cystic lesions occur most often in adults. Occasionally, overlying verrucous lesions are formed, especially in the immunosuppressed patient.


    2. Paranasal sinus phaeohyphomycosis:

    Sinusitis caused by dematiaceous fungi, especially species of Bipolaris, Exserohilum, Curvularia and Alternaria is increasingly being reported, especially in patients with a history of allergic rhinitis or immunosuppression.

    3. Cerebral phaeohyphomycosis:

    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.

    Laboratory Diagnosis:

    1. 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.

    2. 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).

    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.

    3. Culture: 
    Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar.

    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.

    4. Serology: 
    There are currently no commercially available serological procedures for the diagnosis of any of the infections classified under the term phaeohyphomycosis.

    5. 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.

    6. Causative agents:
    Alternaria sp., Aureobasidium pullulans, Bipolaris sp., Cladophialophora bantiana, Verruconis gallopava, Curvularia sp., Exophiala sp., Exserohilum sp., Phialophora verrucosa. 

    Further reading:
    Ajello L and R.J. Hay. 1997. Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections. 9th Edition, Arnold London.
    Ellis MB. 1971 and 1976. Dematiaceous Hyphomycetes and More Dematiaceous Hyphomycetes. International Mycological Institute.
    Hoog de GS et al. 1977. The black yeasts and allied hyphomycetes. Studies in Mycology N0. 15 from Centraalbureau voor Schimmelcultures, Baarn, The Netherlands. CBS publications may be ordered from Tinke van den-Berg-Visser, Centraalbureau voor Schimmelcultures, PO Box 273, 3740 AG Baarn, The Netherlands FAX + 31 2154 16142.
    Hoog de GS and J Guarro. 1994. Atlas of Clinical Fungi from Centraalbureau voor Schimmelcultures, Baarn, The Netherlands. CBS publications may be ordered from Tinke van den-Berg-Visser, Centraalbureau voor Schimmelcultures, PO Box 273, 3740 AG Baarn, The Netherlands FAX + 31 2154 16142.
    Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
    McGinnis MR. 1980. Laboratory handbook of medical mycology. Academic Press [this is out of print but a copy would be a valuable acquisition].
    Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
    Rippon JW. 1988. Medical Mycology WB Saunders Co.
    Warnock DW and MD Richardson. 1991. Fungal infection in the compromised patient. 2nd edition. John Wiley & Sons.

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