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Reduced accumulation of isometamidium by drug-resistant Trypanosoma congolense

Published online by Cambridge University Press:  06 April 2009

I. A. Sutherland ,
A. S. Peregrine ,
J. D. Lonsdale-Eccles  and
P. H. Holmes
I. A. Sutherland
Affiliation:
University of Glasgow Veterinary School, Bearsden Road, Glasgow G61 1QH, UK
A. S. Peregrine
Affiliation:
International Laboratory for Research on Animal Diseases(ILRAD), P. O. Box 30709, Nairobi, Kenya
J. D. Lonsdale-Eccles
Affiliation:
International Laboratory for Research on Animal Diseases(ILRAD), P. O. Box 30709, Nairobi, Kenya
P. H. Holmes
Affiliation:
University of Glasgow Veterinary School, Bearsden Road, Glasgow G61 1QH, UK
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Abstract

The accumulation of the trypanocide isometamidium chloride (Samorin®, RMB Animal Health Ltd, UK) by a range of clones of Trypanosoma congolense with varying sensitivity to the drug, was measured by methods based on the fluorescence of isometamidium. Fluorescence microscopy and flow cytometry showed a reduction in drug accumulation by resistant clones. Fluorescence spectrophotometry demonstrated an inverse correlation between the intensity of cell-associated fluorescence and the level of resistance of the clones expressed in vivo. The addition of the metabolic inhibitor SHAM/glycerol to the incubation medium resulted in a reduction of this apparent difference in drug accumulation between the clones; those clones which were sensitive to isometamidium showed a reduction in fluorescence while a percentage increase in fluorescence was observed as clones became more resistant to the trypanocide. These observations may be of value for the in vitro detection of resistant T. congolense populations and may also be used to estimate the mean level of resistance in a given sample. The results also imply that decreased accumulation of isometamidium by drug-resistant clones of the parasite may be responsible for the reduction in sensitivity.

Keywords

Trypanosoma congolenseisometamidium chloridechemo-resistancedrug accumulation
Type
Research Article
Information
Parasitology , Volume 103 , Issue 2 , October 1991 , pp. 245 - 251
Copyright
Copyright © Cambridge University Press 1991

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