Health care providers treating people living with HIV for cryptococcosis—a serious fungal disease that can affect the lungs and brain—should order tests to identify the microorganism causing the infection, according to a paper published September 1 via the online journal PLoS Pathogens. Though cryptococcosis is usually chalked up to the fungus Cryptococcus neoformans, it could be Cryptococcus gattii, a sibling species that could make a difference in treatment, clinical course and outcome.

Joseph Heitman, MD, PhD, senior author of the study and chair of the Department of Molecular Genetics and Microbiology at Duke University School of Medicine in North Carolina, and his colleagues discovered that in the Los Angeles area, more than 12 percent of people living with HIV/AIDS diagnosed with Crypotococcus were infected with C. gattii—much higher than earlier studies, which suggested that only about 1 percent have C. gattii.

The authors also pointed out that based on the fungal isolate samples taken from patients, those with C. gattii may experience resistance to the commonly used “azole” drugs that combat fungal infections. C. gatti may also be more likely to cause clusters of disease in the central nervous system that can be difficult to treat.

Because cryptococcal strains are responsible for more than 620,000 deaths annually and for one third of all AIDS deaths, this species distinction may be of public health importance. “There may be an unrecognized health burden in AIDS patients attributable to C. gattii rather than C. neoformans,” Heitman said in a Duke University Medical Center press release.

He added that while a simple test is all that is needed to distinguish the two strains, “few clinical microbiology labs or hospitals, even in developed countries, are equipped to distinguish C. neoformans from C. gattii.”

The authors note there isn’t any evidence of human-to-human transmission of C. gattii, but rather, through exposure to Cryptococcosis in the environment. For example, one person living with HIV from San Diego had an isolate that was traced back to a type of tree, which is a common place to find C. gattii, in Australia and elsewhere.

“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 traveling and evolving,” Heitman said.