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Antimicrobial Agents and Chemotherapy, 02 1997, 379-384, Vol 41, No. 2
MT Cushion, F Chen and N Kloepfer
A series of over 60 agents representing several different classes of
compounds were evaluated for their effects on the ATP pools of Pneumocystis
carinii populations derived from immunosuppressed rats. A cytotoxicity
assay based on an ATP-driven bioluminescent reaction was used to determine
the concentration of agent which decreased the P. carinii ATP pools by 50%
versus untreated controls (IC50). A ranking system based on the IC50 value
was devised for comparison of relative responses among the compounds
evaluated in the cytotoxic assay and for comparison to in vivo efficacy.
With few exceptions, there was a strong correlation between results from
the ATP assay and the performance of the compound in vivo. Antibiotics,
with the exception of trimethoprim- sulfamethoxazole (TMP-SMX), were
ineffective at reducing the ATP pools and were not active clinically or in
the rat model of P. carinii pneumonia. Likewise, other agents not expected
to be effective, e.g., antiviral compounds, did not show activity. Standard
anti-P. carinii compounds, e.g., TMP-SMX, pentamidine, and dapsone,
dramatically reduced ATP levels. Analogs of the quinone and topoisomerase
inhibitor groups were shown to reduce ATP concentrations and hold promise
for further in vivo investigation. The cytotoxicity assay provides a rapid
assessment of response, does not rely on replicating organisms, and should
be useful for assessment of structure-function relationships.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
A cytotoxicity assay for evaluation of candidate anti-Pneumocystis carinii agents
Department of Internal Medicine, University of Cincinnati College of Medicine, Ohio 45267-0560, USA. cushiomt@ucbeh.san.uc.edu
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