Penicillium marneffei LPCB Preparation: Introduction, Clinical Features, Lab Diagnosis and Treatment

Penicillium marneffei in LPCB mount

Penicillium marneffei in LPCB mount

Penicillium marneffei LPCB preparation is showing conidiophores that are hyaline, smooth-walled, and bear terminal verticils or whorls of 3-5 metulae, each bearing 3-5 phialides. The conidiophores are described as biverticillate or irregularly monoverticillate. Conidia are globose to subglobose, 2-3 µm in diameter, smooth-walled and are produced in basipetal succession from the phialides.

Penicillium marneffei exhibits thermal dimorphism by growing in living tissue or in the culture at 37°C as a yeast-like fungus, and in the culture at below 30°C as a mold. On SDA (without cycloheximide) at 25°C colonies are fast-growing, suedelike to downy, white with yellowish-green conidial heads. Colonies become grayish-pink to brown with age and produce a characteristic diffusible brownish-red to wine-red pigment

Penicilliosis 

Penicillium marneffei, the dimorphic fungus  causes the disease, which is an
emerging systemic mycosis in AIDS patients as well as other immunocompromised patients. P.  marneffei is endemic in Thailand, Northeastern India, southern China, Hong Kong, Vietnam, and Taiwan in AIDS patients. Bamboo rats and soil are considered the reservoir of the disease through the causative agent has never been isolated from soil except for near bamboo rat burrows. P. marneffei, after tuberculosis and cryptococcosis, is the third most common opportunistic infection in patients with AIDS in the South-East Asia Region and is therefore considered an AIDS-defining illness. People affected by penicilliosis usually have AIDS with low CD4 counts, typically <100/µl.

Clinical Features in Penicilliosis 

Various types of manifestations include:

  • pyrexia ( fever) of unknown origin (PUO), loss of weight, generalized
    lymphadenopathy, anemia
  • hepatomegaly with or without splenomegaly
  • pneumonitis: cough and dyspnea occur in about 50% of cases,
    sometimes with hemoptysis

Laboratory manual for the diagnosis of fungal opportunistic infections in HIV/AIDS patients

  • skin lesions – characteristic generalized papular eruptions, central
    umbilicated papules resembling those of molluscum contagiosum, or acne-like lesions and folliculitis over face, trunk,  and extremities
  • pharyngeal and palatal lesions also can be seen subcutaneous nodules may be seen
  • chest radiographic abnormalities typically manifest as diffuse reticulonodular infiltrates, and cavitations

 Laboratory Diagnosis of Penicillium marneffei

  1. Specimen: Bone marrow aspirate, blood, lymph node biopsy, skin biopsy,
    sputum, BAL, pleural fluid, liver biopsies, CSF, pharyngeal or palatal ulcer,
    scrapings, urine, stool, kidney biopsy, pericardium, stomach or intestinal
    specimens.
  2. Giemsa, Wright, GMS, or PAS stain shows characteristic intracellular (within neutrophils or tissue histiocytes) round to oval yeast-like cells, which may divide by cross wall formation. The cross wall formation can differentiate yeast cells of P. marneffei from those of Histoplasma capsulatum. Elongated sausage-shaped extracellular forms are also seen.
  3. Direct immunofluorescence test is the test of choice for specific diagnosis; this would be done at reference laboratories since it requires a fluorescent microscope.
  4. Definitive diagnosis is based on culture isolation, which has high sensitivity – bone marrow (100%), blood (76%), and skin biopsies (90%). Penicillium  marneffei exhibits thermal dimorphism by growing in living tissue or in the culture at 37°C as a yeast-like fungus, and in the culture at below 30°C as a mold.
  5. Several serological methods for the detection of antibodies or antigens are attempted and produce conflicting results, especially in AIDS patients. e.g. commercially available Pastorex Aspergillus i.e. Latex Agglutination test kit
  6. A specific PCR assay is under evaluation and might be useful as an alternative test for rapid diagnosis of Penicillium marneffei infection.

Treatment of Penicilliosis 

Useful anti-fungal drugs are-

  • Amphotericin B
  • Itraconazole
  • Voriconazole
  • Posaconazole

Further Readings

  1. Medical Mycology. Editors:  Emmons and Binford, 2nd ed 1970, Publisher Lea and Febiger, Philadelphia.
  2. Rippon’s JW: Medical Microbiology. The pathogenic fungi and the Pathogenic Actinomycetes. 3rd ed 1988 Publisher WB Saunder co, Philadelphia.
  3. A Textbook of Medical Mycology. Editor: Jagdish Chander.  Publication Mehata, India.
  4.  Practical Laboratory Mycology. Editors: Koneman E.W. and G.D. Roberts, 3rd ed 1985, Publisher Williams and Wilkins, Baltimore.
  5. https://mycology.adelaide.edu.au/descriptions/hyphomycetes/talaromyces/

 

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