Unexpectedly high rate of multiple strains in fungal infection

[Guest guest]

Public release date: 19-May-2010

Contact: Jim Sliwa

jsliwa@...

202-942-9297

American Society for Microbiology

http://www.eurekalert.org/pub_releases/2010-05/asfm-uhr051910.php

Unexpectedly high rate of multiple strains in fungal infection

New research shows that nearly 1 in 5 cases of infection with the potentially

deadly fungus Cryptococcus neoformans are caused by not one but multiple strains

of the pathogen. Researchers from the Institut Pasteur and the University of

Minnesota Medical School report their findings today in the inaugural issue of

mBio™, the first online, open-access journal published by the American Society

for Microbiology.

" Koch's postulates are criteria establishing a causal relationship between a

microbe and a disease that lead to the assumption that the disease is caused by

a single strain or its evolved forms, " says Françoise Dromer of the Institut

Pasteur, an author of the study. " Using molecular analysis of unpurified

isolates, we demonstrated that mixed infections in humans are more common than

previously thought, occurring in almost 20 percent of patients diagnosed with

cryptococcosis. "

C. neoformans is a life-threatening fungal pathogen that is responsible for an

estimated 1 million cases of meningoencephalitis. It affects up to 30 percent of

HIV-infected patients in sub-Saharan Africa and Southeast Asia and despite

adequate treatment is still fatal in almost 20 percent of cases.

Cryptococcosis is usually considered to represent the reactivation of a dormant

infection. A single isolate of C. neoformans has been thought to be responsible

for the disease, but isolation of numerous different strains at the same

geographic site suggested infection with multiple stains was possible. Only

anecdotal reports of mixed infections have been published to date.

The researchers analyzed clinical cultures collected during a prospective study

on cryptococcosis. Using molecular analysis of unpurified isolates they

uncovered an unexpectedly high frequency (almost 20 percent) of mixed

infections. They further demonstrated that these mixed infections could result

from infestation by multiple strains acquired from the environment and that the

strains were also evolving during infection.

" The concept of one strain/one infection does not hold true for C neoformans and

may apply to other environmentally acquired fungal pathogens. The possibility of

mixed and/or evolving infections should be taken into account when developing

therapeutic strategies against these pathogens, " says Dromer.

###

mBio™ is a new open access online journal published by the American Society for

Microbiology to make microbiology research broadly accessible. The focus of the

journal is on rapid publication of cutting-edge research spanning the entire

spectrum of microbiology and related fields. The inaugural issue launches

Tuesday, May 18 and can be found online at http://mbio.asm.org .

The American Society for Microbiology, headquartered in Washington, D.C., is the

largest single life science association, with 40,000 members worldwide. Its

members work in educational, research, industrial, and government settings on

issues such as the environment, the prevention and treatment of infectious

diseases, laboratory and diagnostic medicine, and food and water safety. The

ASM's mission is to gain a better understanding of basic life processes and to

promote the application of this knowledge for improved health and economic and

environmental well-being.