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Antimicrobial Agents and Chemotherapy, December 2000, p. 3302-3305, Vol. 44, No. 12
Division of Infectious Diseases,
Department of Medicine, Santa Clara Valley Medical Center, and
California Institute for Medical Research, San
Jose,1 and Stanford University School of
Medicine, Stanford,2 California
Received 24 April 2000/Returned for modification 19 June
2000/Accepted 28 August 2000
There have been several reports that the activity of echinocandin
antifungal agents is not affected or decreased in the presence of
human sera. It is known that these drugs are bound >80% in animal and
human sera. The activity of the echinocandin caspofungin (MK-0991), a
1,3-
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Influence of Human Sera on the In Vitro Activity of the
Echinocandin Caspofungin (MK-0991) against Aspergillus
fumigatus
-D-glucan synthase inhibitor, against
Aspergillus fumigatus with and without human sera was
studied. Conidia of A. fumigatus in microtest plate wells
formed germlings after overnight culture in RPMI 1640. Caspofungin was
then added with or without serum, and the germlings were incubated at
37°C for 24 h. Human serum (5%) in RPMI 1640 alone did not
significantly inhibit the growth of A. fumigatus in vitro.
Caspofungin in RPMI 1640 exhibited dose-dependent inhibition, with
concentrations of 0.1 and 0.05 µg/ml inhibiting 24.9% +/
10.4%
and 11.7% +/
3.6%, respectively (n = 10;
P < 0.01). The addition of 5% human serum to
caspofungin at 0.1 or 0.05 µg/ml increased the
inhibition to 78.6% +/
5.8% or 58.3% +/
19.2%,
respectively (n = 10; P < 0.01 versus controls and versus the drug without serum). Lower
concentrations of serum also potentiated drug activity. The effect of
human sera was further seen when using caspofungin that had lost
activity (e.g., by storage) against A. fumigatus at
0.1 µg/ml. Inactive caspofungin alone demonstrated no
significant inhibition of hyphal growth, whereas the addition of 5%
human serum to the inactive drug showed 83% +/
16.5% inhibition
(n = 5; P < 0.01). The restoration
of activity of caspofungin was seen at concentrations as low as 0.05%
human serum. In contrast to prior reports, this study suggests
that human serum acts synergistically with caspofungin to enhance its inhibitory activity in vitro against A. fumigatus.
*
Corresponding author. Mailing address: Division of
Infectious Diseases, Department of Medicine, Santa Clara Valley Medical Center, 751 S. Bascom Ave., San Jose, CA 95128-2699. Phone: (408) 885-4307. Fax: (408) 885-4306. E-mail:
chiller{at}leland.stanford.edu.
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