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06-09-2011 | General practice | Article

Cryptococcus infections misdiagnosed in many HIV or AIDS patients

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MedWire News: Research suggests that many patients with HIV or AIDs who are diagnosed with cryptococcosis are assumed to be infected with Cryptococcus neoformans, when many are actually infected with Cryptococcus gattii.

This could mean that treatment of these patients is not being optimized, as treatment for C. gattii may be more complex than that for C. neoformans, including the potential risk for azole drug resistance and formation of cryptococcomas in the central nervous system that are difficult to treat and can result in abscesses.

Joseph Heitman (Duke University, Durham, North Carolina, USA) and colleagues investigated the prevalence of C. gattii as opposed to the related C. neoformans in HIV/AIDS patients with cryptococcosis.

They compared isolates from Californian patients with those from a global collection.

Through molecular testing of fungal DNA, the team found that 12% or more of HIV/AIDS patients in the Los Angeles area of California who were diagnosed with cryptococcosis had C. gattii infection, a much higher figure than the previously suggested estimate of around 1%.

"There may be an unrecognized health burden in AIDS patients attributable to C. gattii rather than C. neoformans," said Heitman.

The investigators stress the importance of this finding as over a million patients are infected with life-threatening cryptococcosis every year, which causes a third of all deaths related to AIDS.

Heitman explained that while it is fairly simple to distinguish between the two strains using a simple test, "few clinical microbiology labs or hospitals, even in developed countries, are equipped to distinguish C. neoformans from C. gattii."

The researchers believe that the increase in C. gattii infection is likely to be linked to environmental exposure rather than human-to-human transmission, for example one US patient had an isolate of the fungus that was traced back to a tree.

"This study clearly illustrates that AIDS patients in certain areas of the world might be infected by two different cryptococcal species," said John Perfect, also from Duke University Medical Center.

"Although the outcome of infection in comparison between the two species remains uncertain, this study shows that we need to carefully control for potential differences and study them further."

Heitman concluded: "Based on the prevalence we found, it makes sense to pursue further clinical studies, not just to find out the species, but also the molecular type, so we can learn all we can about how this pathogen is travelling and evolving."

By Helen Albert

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