Monday, October 04, 2010

Put Cryptococcus gattii on the radar screen

From MMWR:

Cryptococcus is a genus of fungi, of which two species, Cryptococcus neoformans and Cryptococcus gattii, cause nearly all human and animal cryptococcal infections. Whereas C. neoformans primarily affects persons infected with human immunodeficiency virus (HIV) worldwide, C. gattii primarily affects HIV-uninfected persons in tropical and subtropical regions (1). In December 2004, a case of human C. gattii infection was reported in Oregon, associated with an outbreak on Vancouver Island and in mainland British Columbia, Canada (2). A second C. gattii case was reported in Oregon in 2005, and 12 more cases were reported in 2006 and 2007. In 2008, in response to the emergence of C. gattii in the United States, CDC, state and local public health authorities, and the British Columbia Centre for Disease Control (BCCDC) formed the Cryptococcus gattii Public Health Working Group (1). States began collecting epidemiologic information on patients and sending isolates to CDC. By July 2010, a total of 60 human cases had been reported to CDC from four states (California, Idaho, Oregon, and Washington) in the Pacific Northwest. ..

Physicians should consider C. gattii as a possible etiology of a cryptococcal infection among persons living in or traveling to the Pacific Northwest or traveling to other C. gattii--endemic areas...

Among the 45 patients for whom outcome was known, nine (20%) died because of C. gattii infection and six (13%) died with C. gattii infection; two of the nine who died from C. gattii infection had no predisposing condition...

C. gattii is an emerging infection in the United States. C. gattii appears to differ from its sibling species, C. neoformans, both in its clinical aspects (e.g., less responsive to antifungal drugs and more likely to cause tumor-like lesions called cryptococcomas) and its ecologic niche (2,8). In addition, whereas the primary risk factor for C. neoformans cryptococcosis is severe immunosuppression (e.g., from HIV infection), risk factors for C. gattii infection in the United States appear to include both immunocompromise and exposure to specific regions of environmental fungal colonization (2,8).

So the important differences from C neoformans appear to be more pulmonary involvement as opposed to CNS (although it does cause CNS infection), a greater tendency to form cryptococcomas and less association with HIV infection. Many patients were known to be immunosuppressed but apparently some had no identifiable factors. These features---the increased pulmonary involvement, the less well defined association with immunosuppression and the geographic distribution make this infection look a bit more like an endemic fungus although that characterization may not be completely accurate.

Although the article indicates that C. gattii tends to be treatment resistant I could find very little in the literature, including UptoDate, that specifically addresses treatment of C gattii as opposed to C neoformans. Apparently the same agents are used although perhaps more heavily weighted towards ampho. Fluconazole is still advocated for consolidation therapy although reports of heteroresistance are concerning.

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