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  those 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 culture at 37°C as a yeast-like fungus, and in culture at below 30°C as a mould. 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 brownishred to wine-red pigment

Penicilliosis marneffei

Penicillium marneffei, the dimorphic fungus  causes the disease, which is an
emerging systemic mycosis in AIDS patients as well as other  immunocompromized 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 though the  causative agent has never been isolated from soil except 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 

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 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 cell of P. marneffei from those of Histoplasma capsulatum. Elongated sausageshaped extracellular forms are also seen.
  3. Direct immuno-fluorescence 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 a high sensitivity – bone marrow (100%), blood (76%) and skin biopsies (90%). Penicillium  marneffei exhibits thermal dimorphism by growing in living tissue or in culture at 37°C as a yeast-like fungus, and in culture at below 30°C as a mold.
  5. Several serological methods for 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 

Useful anti-fungal drugs are-

  • Amphotericin B
  • Itraconazole
  • Voriconazole
  • Posaconazole

Reference

  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 Text Book of Medical Mycology. Editor: Jagdish Chandar.  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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