LETTER TO EDITOR
Year : 2010 | Volume
: 53 | Issue : 4 | Page : 855--856
Prevalence of Cryptococcus gattii causing meningitis in a tertiary neurocare center from south India: A pilot study
S Nagarathna1, HB Veena Kumari1, N Arvind1, A Divyalakshmi1, A Chandramuki1, P Satishchandra2, V Ravi3,
1 Department of Neuromicrobiology, National Institute of Mental Health and Neuro Sciences, Bangalore, India
2 Department of Neurology, National Institute of Mental Health and Neuro Sciences, Bangalore, India
3 Department of Neurovirology, National Institute of Mental Health and Neuro Sciences, Bangalore, India
Department of Neuromicrobiology, NIMHANS, Hosur Road, Bangalore - 560 029
|How to cite this article:|
Nagarathna S, Veena Kumari H B, Arvind N, Divyalakshmi A, Chandramuki A, Satishchandra P, Ravi V. Prevalence of Cryptococcus gattii causing meningitis in a tertiary neurocare center from south India: A pilot study.Indian J Pathol Microbiol 2010;53:855-856
|How to cite this URL:|
Nagarathna S, Veena Kumari H B, Arvind N, Divyalakshmi A, Chandramuki A, Satishchandra P, Ravi V. Prevalence of Cryptococcus gattii causing meningitis in a tertiary neurocare center from south India: A pilot study. Indian J Pathol Microbiol [serial online] 2010 [cited 2021 Jun 15 ];53:855-856
Available from: https://www.ijpmonline.org/text.asp?2010/53/4/855/72001
Cryptococcosis is a systemic mycosis with predilection for central nervous system, caused by Cryptococcus neoformans, with three distinct varieties - Cryptococcus neoformans var grubii (serotype A), C. neoformans var gattii (serotypes B and C), and C. neoformans var neoformans (serotype D). The biological and genetic differences of var gattii are so substantial that it has been recognized as a separate species, C. gattii.  The varieties grubii and neoformans are found worldwide, mainly affecting immunocompromised patients, causing acute meningitis or meningoencephalitis. On the contrary, C. gattii is aggressive, predominantly infecting immunocompetent persons, causing intracranial mass lesions (cryptococcomas), also causing meningitis in immunocompromised.  C.gattii has been traditionally restricted to tropical and subtropical countries. However, the recent outbreak in temperate climates has raised strong possibilities of broader distribution, emphasizing on continuous surveillance.  Identification of C.gattii is also important, as it is relatively refractory to prolonged course of treatment besides the sequelae.
With this background, we aimed to identify and assess the rate of C. neoformans varieties, especially C.gattii, causing meningitis in relation to HIV status.
The study material comprised of 418 cryptococcus isolates grown on Sabourauds dextrose agar (SDA), from cerebrospinal fluid (CSF) of 418 clinically suspected cases of Cryptococcal meningitis, for a period 6 years 4 months (76 months) in a large tertiary care neurocenter of South India. The nonpathogenic and pathogenic strains were differentiated from each other on the ability of the latter to produce melanin on caffeic acid agar medium, urease production and growth at 37°C. These isolates were further characterized on the exclusive ability of C. gattii to utilize l-canavanine and assimilate glycine as the sole carbon source, on an improved diagnostic l-canavanine glycine bromothymol blue (CGB) agar.  The HIV status of the patients was assessed, as per the guidelines of the National AIDS Control Organisation (NACO, New Delhi, India).
The age-range was 10-80 years in the affected group, of which 80% (335) were males with young adults being predominant. Of 418 isolates, 12 (2.8%) were var gattii and 406 (97.2%) were either var neoformans/grubii. HIV status was available in 358 (85.6%) cases and 338 (94.4%) were seropositive and 20 (5.6%) seronegative. Of the seropositives, 331 (98%) were var neoformans/grubii and 7 (2%) were C. gattii. Of the 20 seronegative cases, 16 were var neoformans/grubii and 4 (20%) were C. gattii.
Globally, all cases of Cryptococcosis in AIDS patients are due to var grubii, followed by var neoformans. In the geographical areas endemic to C.gattii, AIDS patients are infected almost exclusively with the variety grubi.  But the recent outbreak of C.gattii infection on Vancouver island in Canada indicated a striking change in the distribution. 
There are few reports of C. gattii being isolated from clinical as well as environmental sources from North and South India, suggesting the widespread reservoir of this fungus. In India, first case of C.gattii infection in an AIDS patient was reported by Abraham et al.  Padhey et al.  reported three cases of C.gattii meningitis. Marriott et al.  recorded five cases of cryptococcal meningitis of the seven HIV patients infected with C.gattii.
Our observations highlight the fact that the rate of C.gattii in this part of the country is low (2.8%) in comparision to a study from South Africa, which has reported 2.4% and that C.gattii can cause meningitis in immunocompromised individuals as well.
In this pilot study, we have attempted to biochemically differentiate C.gattii from other varieties. However, it is essential to perform molecular studies to confirm and establish incidence of the varieties. Further studies are needed to investigate the possible coexistence of HIV with different serotypes and genotypes of C. neoformans varieties and their clinical outcome.
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