Studies On In Vitro Assessment Of "drug Resistance" In Trypanosoma Vivax
Abstract
Six stocks of Trypanosoma vivax were investigated for their drug
sensitivity to isometamidium chloride and diminazene aceturate. It was
evaluated whether in vitro tests had the potential to distinguish between
drug-sensitive and drug-resistant stocks of T vivax. Four in vitro
tests were employed in drug sensitivity assessment: (1) Long Term
Viability Assay (20 days) with insect forms at 27 C, (2)
3H-Hypoxanthine Incorporation Test (48 hrs) with bloodstream forms at
340C, (3) Drug Incubation Infectivity Test (DIIT) with bloodstream
forms at 370C and (4) Drug Incubation Survival Test with bloodstream
forms at 340C. All tests were able to show an antitrypanosomal effect
of both, isometamidium chloride and diminazene aceturate on T vivax in
vitro. The antitrypanosomal effects were detected by rounding and death
of epimastigotes, inhibition of 3H-Hypoxanthine incorporation by
bloodstream forms, loss of infectivity to mice and reduction in the
number of survivors.
The Long Term Viability Assay and the Drug Incubation Survival
Test showed potential to distinguish between isometamidium
chloride-sensitive and isometamidium chloride-resistant stocks or clones .
of T vivax. Results on drug sensitivity of T vivax stocks obtained
with these tests correlated with results in cattle or mice. A
correlation between in vitro and in vivo results was not observed
regarding diminazene aceturate.
When cattle were infected with in vitro produced metacyclics,
resistance of bloodstream forms of T vivax stock CP 2171 was retained to
treatment with 0.5 and 1.0 mg/kg isometamidium chloride after continuous
in vitro propagation of epimastigotes for 30 months. The reduced
sensitivity of epimastigotes of CP 2171 to isometamidium in vitro was
similar in cultures initiated from these cattle compared with results
obtained in cultures initiated from cattle infected with the original
stabilate.
Citation
Master of . Science in Veterinary Pathology and Microbiology at the University of Nairobi, 1990Publisher
University of Nairobi, Department of Veterinary Pathology and Microbiology