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PSEUDALLESCHERIA BOYDII BRAINABSCESS IN AN IMMUNOCOMPROMISED HOST

Lina Deodhar*, Priya Miskeen*, Al Kirpalani**,Jinni Jagose**, Shubhu Sarkar**
*Departments of Microbiology and **Nephrology Bombay Hospital Institute of Medical Sciences, Mumbai.

Pseudallescheria boydii (P. boydii) is commonly listed as an aetiological agent of mycetoma but can cause infections elsewhere in immunocompromized hosts. A male patient 41 year old, who underwent renal transplant surgery, developed brain abscess six months after the surgery. P. boydii was isolated from the aspirate of the brain. Till 1990, only 20 cases of brain lesions caused by this fungus have been reported in world literature. Therefore this case has been reported.

The common diseases of the central nervous system (CNS) include meningitis and space occupying lesion (SOL) of the brain. The latter may present as a granuloma, an abscess or a tumour. A brain abscess is formed, when there is localized collection of pus, in a cavity formed by the breakdown of the tissue, in the brain. [1] The aetiological agents of brain abscess include bacteria, fungi and parasites. Amongst the fungi, aspergillus and candida species and Cryptococcus neoformans are the common causative agents of brain abscess. Pseudallescheria boydii (P. boydii) is listed as the aetiologic agent of mycetoma but can cause infections elsewhere in immunocompromised hosts. We are reporting a case of P. boydii brain abscess in a patient who had undergone renal transplant surgery.

CASE REPORT

A male patient aged 41 years, was admitted in the hospital in May 1999 with the history of headache and convulsions lasting for one minute followed by unconsciousness for 3-4 minutes. Patient had undergone renal transplant surgery in December 1998. Patient was receiving immunosuppressant drugs and also AKT treatment for suspected tubercular meningitis. On admission, patient was febrile. His blood culture was sterile and malarial parasites were not detected in blood smears. However, MRI showed "changes in left frontal lobe of the brain suggestive of an infective granuloma". A frontal burrhole was done and pinkish jellylike fluid was aspirated and sent for routine cultural examination. A second sample was received after a gap of ten days. Patient was put on amphotericin-B; however he expired within four days after the second burrhole operation. The cause of death was given as "cardio-respiratory arrest with fungal brain abscess with chronic renal failure."

Microbiological findings

In both the samples, no bacteria were grown. The first sample showed a white fluffy colony on blood agar on fourth day and therefore a fungal aetiology was suspected. In the repeat sample, KOH wet mount showed hyaline, septate hyphae. Culturing on sabouraudís dextrose agar medium with chloramphenicol revealed fluffy whitish growth of the fungus and the reverse of the growth showed brownish black colour after 10 days. (Photograph 1 and 2). KOH wet mount of the colony revealed single celled conidia borne singly on short conidophores which were attached to the mycelium. The colony characteristics and the microscopical appearance was suggestive of Pseudallescheria boydii (P. boydii).

DISCUSSION

P. boydii rarely affects the CNS and till 1990 only 20 cases of brain lesions caused by this fungus have been reported in the world literature. [2] The predisposing factors in such patients are immunosuppression associated with lymphoma, systemic lupus, subacute glomerulonephritis, diabetes mellitus or renal transplant. In the present case, patient had undergone renal transplant operation and was also taking immunosuppressive drugs.

 Pseudallescheri boydii - fluffy  white colonies on Sabouraud’s medium
Fig 1
Pseudallescheri boydii - fluffy white colonies on Sabouraudís medium


P. boydii
is a natural inhabitant of soil, manure and polluted water. [2] Route of infection to CNS is aspiration of the fungus to the lungs producing pulmonary infection and then leading to dissemination of the fungus to the brain. Alternatively, this fungus can gain entry through fracture in the skull or paranasal sinuses.

Pseudallescheriasis resembles aspergillosis both clinically and pathologically. [3] There are no rapid diagnostic techniques for identifying the hyphae as P. boydii and there are no specific tests available for the detection of antigen or antibody. [3]

P. boydii infection of the CNS carries a high mortality. Out of 20 cases described in world literature only four patients have survived.

Antifungal therapy for P. boydii is complicated because most strains are resistant to amphotericin-B. Therefore the drug of choice is miconazole or ketoconazole.

 Pseudallescheria boydii brownish black colour on reverse side of the medium
Fig 2
Pseudallescheria boydii brownish black colour on reverse side of the medium


REFERENCES

  1. Forbes BA, Sahm DF, Weissfeld AS (editors). "Bailey and Scotts Diagnostic Microbiology" Tenth edition, publishers Mosby. 1998; 65 : 936, 334.
  2. Kreshaw P, Freeman R, Templeton D, et al. "Pseudallescheria boydii infection of the central nervous system". Arch Neurol 1990; 47 : 468-72.
  3. Mandell GL, Bennett JE, Dolin R (editors). "Mandell, Douglas and Bennettís Principles and practice of Infectious Diseases". Fourth edition. Publishers Churchill Livingstone. 1995; 2 (249) : 2390.

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