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Aspergillus terreus Resistant to Amphotericin B


NEW YORK (Reuters Health) Jul 25 - Aspergillus terreus is an emerging
fungal pathogen that is resistant to amphotericin B. The pathogenesis
and treatment of this lethal organism are reviewed in the July 15th
issue of the Journal of Infectious Diseases.

According to the multicenter team of authors, led by Dr. Thomas J.
Walsh of the National Cancer Institute in Bethesda, Maryland, most
cases of invasive pulmonary aspergillosis are caused by A. fumigatus.
Increasingly, however, amphotericin-resistant cases of pulmonary
aspergillosis caused by A. terreus are reported.

When the researchers ****yzed A. terreus, their results confirmed that
the organism is "resistant in vitro and in vivo to the fungicidal
effects of amphotericin B." They also discovered that amphotericin
resistance correlated with galactomannan antigenemia.

In rabbits with persistent neutropenia, A. terreus produced pulmonary
infarctions, angioinvasion, and thrombosis of pulmonary arteries and
veins. "Although A. terreus was less virulent than A. fumigatus in
vivo, this organism [could not be] eradicated from pulmonary tissue"
in the animals, the authors said.

The researchers did find, however, that "the antifungal triazoles,
posaconazole and itraconazole, exerted significantly more antifungal
activity [than amphotericin] in pulmonary aspergillosis due to A.
terreus." With administration of these agents, galactomannan
antigenemia resolved, residual fungal burden was reduced, and survival
was improved.

The authors point out that rapid differentiation of A. fumigatus and
A. terreus is important. "This study found in vivo formation of
aleurioconidia along the lateral walls of hyphal elements of A.
terreus," they report. "To our knowledge," they add, "A. terreus is
the only medically important species of Aspergillus that produces
aleurioconidia in vivo."

"Recognition of these aleurioconidia in clinical specimens, such as
bronchoalveolar lavage, fine need aspirates, or biopsies, may permit
a preliminary identification of A. terreus and the initiation of an
antifungal triazole," the authors suggest.

J Infect Dis 2003; 188:305-319.

http://www.medscape.com/viewarticle/459304?mpid=16717