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Cryptococcus gattii emerging in HIV/AIDS population
Byrnes EJ 3rd. PLoS Pathog. 2011;doi:10.1371/journal.ppat.1002205.
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Cryptococcus gattii may be more common than previously thought and has caused a significant number of infections in the HIV/AIDS population.
For the study, C. gattii infections reported among patients with AIDS in Los Angeles County were compared with C. gattii infections currently causing an outbreak in the Pacific Northwest.
“This outbreak began in 1999 on Vancouver Island in both patients and animals, and has since spread to the Canadian mainland and into the US in Washington, Oregon and, possibly now, northern California,” Joseph Heitman, MD, PhD, chair of the department of molecular genetics and microbiology at Duke University Medical Center, told Infectious Disease News. “We were concerned that the cases in southern California might also have been a result of the isolates causing the more northern outbreak.”
Microbiological, genetic and genomic analyses of isolates indicated that 93% of isolates infecting HIV/AIDS patients in Los Angeles County were of VGIII molecular type and not the VGII molecular type causing the outbreak in the Pacific Northwest.
Heitman and colleagues said the VGIII type infecting HIV/AIDS patients showed decreased levels of virulence vs. the Pacific Northwest VGII type.
“The importance of this study is in documenting that AIDS patients are at risk for infection by a distinct form of a common pathogenic fungus,” Heitman said. “Not only are they at risk for infection by C. neoformans, which causes up to one-third of all AIDS-related deaths, but they are also at risk for infection by C. gattii. In this context, an important distinction is that C. gattii is more commonly associated with infections in patients without immunosuppression or with diseases that may compromise immunity other than AIDS.”
The researchers said these findings suggest a significant burden of C. gattii may be unrecognized, “with potential prognostic and therapeutic implications. These results signify the need to classify pathogenic Cryptococcus cases and highlight possible host differences among the C. gattii molecular types influencing infection of immunocompetent (VGI/VGII) vs. immunocompromised (VGIII/VGIV) hosts.” – by Ashley DeNyse
Disclosure: The research was supported by NIH/NIAID.
The HIV epidemic continues to inform and change the practice of infectious diseases. Infections once considered rare become common in those whose HIV infection has compromised their immune status; lessons learned there can help us understand diseases in the more general population. Fungal infections represent a major disease burden in the HIV-infected population world-wide. Meningitis caused by cryptococci is especially common in Africa. In the US, cryptococcal meningitis is now uncommon except in those with extremely low CD4 cell counts - typically persons never treated with antiretroviral therapy. While almost all cases here are with cryptococcus neoformans, reports have increasingly surfaced of infection with the other major species - cryptococcus gatti. The authors of this article performed detailed analysis of a number of cryptococcal isolates from a California cohort and found a number of cases of a variant of C. gatti (VGIII) distinct from a previously reported outbreak in the Pacific Northwest. Further sub-typing identified molecular details of C. gatti that might predict the severity of associated human disease. The prevalence of molecular subtypes of cryptococcal organisms varies regionally depending on climate and the soil and vegetation in which it resides. Better characterization using the molecular techniques described in this paper might allow better prediction of the specific variants expected in immune compromised patients and possibly how they are clinically affected and managed.
– Paul A. Volberding, MD
Infectious Diseases News Chief Medical Editor
Disclosure: Dr. Volberding reports no relevant financial disclosures.
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