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Year : 2004  |  Volume : 22  |  Issue : 3  |  Page : 188-190

Unusual morphological forms of cryptococcus neoformans in cerebrospinal fluid

Department of Clinical Microbiology and Medicine, Pondicherry Institute of Medical Sciences, Pondicherry - 605 006, India

Date of Submission01-Mar-2004
Date of Acceptance01-Apr-2004

Correspondence Address:
Department of Clinical Microbiology and Medicine, Pondicherry Institute of Medical Sciences, Pondicherry - 605 006, India

 ~ Abstract 

Cryptococcal meningitis is recognized as one of the AIDS defining conditions. It acts as a diagnostic marker for further investigations to establish the retroviral infection. Cryptococcus neoformans can be readily identified by its characteristic capsulated morphology. But rarely variations in morphology may be seen. We report a case of chronic meningitis in an AIDS patient whose cerebrospinal fluid (CSF) stained with India ink showed elliptical, peanut shaped and pseudomycelial large yeast cells with thick capsules. The organism was cultured and identified as Cryptococcus neoformans var neoformans. Unusual morphological forms may create diagnostic dilemma in the rapid diagnosis of cryptococcal meningitis.

How to cite this article:
Shashikala, Kanungo R, Srinivasan S, Mathew R, Kannan M. Unusual morphological forms of cryptococcus neoformans in cerebrospinal fluid. Indian J Med Microbiol 2004;22:188-90

How to cite this URL:
Shashikala, Kanungo R, Srinivasan S, Mathew R, Kannan M. Unusual morphological forms of cryptococcus neoformans in cerebrospinal fluid. Indian J Med Microbiol [serial online] 2004 [cited 2020 Oct 25];22:188-90. Available from:

Cryptococcal meningitis is one of the AIDS defining conditions. It is important to recognise the organism in clinical specimen for rapid diagnosis. Cryptococcus can be readily identified by its characteristic capsulated morphology. Rarely, variations in morphology may be seen. It may appear in various sizes and shapes with large thick capsule or even absence of capsules in some. It is not known, what factors influence the appearance of these unusual morphological forms in clinical material. We report a case of cryptococcal meningitis whose cerebrospinal fluid showed varied forms of the yeast.

 ~ Case Report Top

A 56 year old male was admitted to this hospital with fever, vomiting, headache and drowsiness for 7 days .He had been treated for tuberculosis one year back with a course of ATT for nine months. He also had history of bowel and urinary incontinence. On examination, patient had a temperature of 39C, heart rate 90/minute and blood pressure of 130/70 mm Hg. Respiratory and cardiovascular systems were normal. Abdomen was soft with normal bowel sound. The liver and spleen were not palpable. Central nervous system examination revealed altered sensorium, responding to oral commands only. He had neck stiffness, sluggish deep tendon reflexes and planter extensor on right side. Liver function tests were normal and haemogram was within normal limits. Other parameters included ESR-115 mm/hr, urea-23 mg%, and creatinine-0.9 mg%. CSF cell count showed lymphocyte predominance (98%) with glucose-28 mg/dL and protein-57 mg/dL. Fasting blood sugar was119 mg%. Computer aided tomography showed minimal hydrocephalus with dilated ventricles.

 ~ Microbiological investigations Top

Gram smear of CSF showed moderate number of lymphocytes with poorly stained round to oval yeast cells. India ink staining of CSF showed capsulated budding yeast cells of different forms [Figure - 1]a-f.
Some were round capsulated budding yeast cells. Others were oval, peanut shaped and leaf shaped. Capsules and cell walls were thickened in most of the forms. Size of the cells were larger than the normal size of 4-10m [Figure:2]. On Sabouraud dextrose agar, smooth, cream coloured, mucoid colonies were grown at 37C within 48 hours. India ink staining of culture suspension showed non-capsulated yeast cells smaller in size than that of CSF smear.
The organism was characterized by growth on eucalyptus agar,[1] production of urease enzyme at 37oC and effect of EDTA on urease activity.[2] Eucalyptus agar did not support the growth of the isolate and urease enzyme was produced at 37oC. This activity was not inhibited by exposure to EDTA. Based on these findings, the isolate was presumptively identified as Cryptococcus neoformans var neoformans. Culture of CSF for pyogenic organisms on standard media did not yield any bacterial growth. Bacterial cultures of blood and urine by standard bacteriological methods did not yield any organism.[3] Sputum smear was negative for acid fast bacilli. Endotracheal tube culture grew methicillin resistant Staphylococcus aureus   (MRSA). Serum was reactive for HIV 1 antibodies by ELISA (Span Diagnostics, Mumbai) and HIV TRI-DOT test (rapid immunoassay by J.Mitra & Co. Ltd., New Delhi).
The patient was admitted in the ICU. Injection ceftriaxone 2gm. IV twice daily, ATT and anti-cerebral edema measures were started. Within two weeks, the patient developed central cyanosis with cold peripheries. He also developed MRSA nosocomial pneumonitis which was treated with tablet linezolid 600mg twice daily and injection chloramphenicol 500mg four times a day. The patient was also started on intravenous injection of amphotericin B (0.7mg/kg/day) with oral fluconazole 200mg/day. Inspite of these measures, the patient succumbed to his illness.

 ~ Discussion Top

Cryptococcosis, an uncommon disease before the AIDS epidemic, has emerged as an important cause of illness and death in HIV infected persons. A dramatic increase of cryptococcal infections has been observed with the advent of the AIDS pandemic and since then HIV infections have accounted for more than 80% of the predisposing factors.[4] Consequently, diagnosis of cryptococcosis in patients with an unknown predisposition always suggests an evaluation for HIV infection. Extrapulmonary cryptococcosis in HIV infected individuals is pathognomonic for AIDS.[5] The prevalence of cryptococcal infections among AIDS patients varies from 2-10% in Western Europe and the United States and upto more than 15% in central Africa and South east Asia.[6]
Nearly 10-20% of patients succumb to infection in medically advanced countries while the mortality rate is more than 50% within two weeks of diagnosis in developing countries due to paucity of diagnostic facilities and high cost of treatment.[6]
Cryptococcus neoformans is a heterothallic encapsulated yeast. Microscopically the unicellular cells of the fungus are spherical to oval in shape. Individual cells are surrounded by a polysaccharide capsule. The diameter of the cell can vary from 2-5 m (capsule deficient) to 30-80 m in heavily encapsulated cells.[7] Recognition of variants in morphology of the organisms is important in laboratory confirmation of the disease. Characteristic morphology of C.neoformans does not pose any difficulty in recognizing the fungus. But unusual forms may be produced in clinical material which can give rise to diagnostic dilemma. Cruickshank et al have reported a case of primary cryptococcosis of lungs where giant cells of C.neoformans were seen in the pleural fluid. They demonstrated thick capsules.[8] Average size of the isolates was over 40 m and it was associated with enlargement of the cytoplasm, cell wall and capsule. However, upon culturing in artificial media, the organism reverted to a normal size. A rare morphology of hand mirror appearance in direct microscopic examination of both CSF and sputum from a patient with AIDS has been reported by Anandhi et al.[9] Present isolate also demonstrated features of large capsule, thick cell wall and variant shapes.
Large size of cell with thickening of the wall and increased melanin deposit have been demonstrated during the course of experimental infection in mice.[10] Morphological changes are potentially relevant to cryptococcal pathogenesis. New cellular forms arising from the changes stimulated by the growth may lead to altered antigenic epitopes resulting in difficulty by the host to mount immune response. Researchers hypothesise that the infection is dynamic with respect to yeast cell morphology and giant cell forms arise in tissue during the course of infection.[10] Evidence of whether these forms are more virulent than the others have not been documented. Further studies are required to determine whether the unusual forms of Cryptococcus neoformans in clinical material are more virulent and alter the course of infection in patients. 

 ~ References Top

1.Hazen KC, Howell SA. Candida, Cryptococcus and other yeasts of Medical Importance in Manual of Clinical Microbiology. Editors Murray PR, Baron EJ, Jorgensen JH, Faller MAP, Yolken RH. 8th edition, Vl2, ASM Press, Washington 2003.  Back to cited text no. 1    
2.Kwon-Chung KJ, Wickes BL, Booth JL, Vishniac HS, Bennett JE. Urease inhibition by EDTA in the two varieties of Cryptococcus neoformans. Infect Immun 1987;55(8):1751-1754.  Back to cited text no. 2    
3.Collee JG, Diguid JP, Fraser AG, et al. Mackie and McCartney Practical Medical Microbiology. 14th edition, Churchill Livingstone, Edinburgh 1996.  Back to cited text no. 3    
4.Dromer F, Mathoulin S, Dupont B, Laporte A. Epidemiology of cryptococcosis in France: a 9 year survey (1985-1993). Clin Infect Dis 1996;23(1):82-90.  Back to cited text no. 4    
5.Dismukes WE. Cryptococcal meningitis in AIDS. J Infect Dis 1998;157:624-628.  Back to cited text no. 5    
6.Hajjeh RA, Conn LA, Stephen DS, Baughman W, Hamill R, et al. Cryptococcosis: population based multistate active surveillance and risk factors in human immunodeficiency virus infected persons. J Infect Dis 1999;179:449-454.  Back to cited text no. 6    
7.Viviani MA, Tortorano AM, Ajello L. Clinical Mycology. Anaissie EJ, et al 1st Edn, Churchill Livingstone, Edinburgh. 2003.  Back to cited text no. 7    
8.Cruickshank JG, Cavill R, Jelbert M. Cryptococcus neoformans of unusual morphology. Appl Microbiol 1973;125(2):309-312.  Back to cited text no. 8    
9.Anandi V, Babu PG, John TJ. Infection due to Cryptococcus neoformans of unusual morphology in a patient with AIDS. Mycoses 1991;34:377-379.  Back to cited text no. 9    
10.Feldmesser M, Kressy, Casadevall. Dynamic changes in the morphology of Cryptococcus neoformans during murine pulmonary infection.  Back to cited text no. 10    
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2004 - Indian Journal of Medical Microbiology
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