Antigiardial Drugs Research Articles

A radiometric assay for antigiardial drugs

Susceptibility of Giardia lamblia trophozoites to 3 antigiardial drugs was determined morphologically by 24h parasite counts and radiometrically by uptake of [ 3H]thymidine and by rapid 4h microassays of motility and viability. Growth of Giardia trophozoites in liquid culture correlated well with uptake of [ 3H]thymidine during a 72h period ( r = 0·91, P < 0·01). ED 50 and MIC for metronidazole, mepacrine and sodium fusidate were similar in both morphological and radiometric growth assays and, except for mepacrine, results were similar to previously reported drug efficacies obtained with more labour intensive methods. Motility and viability 4h microassays were insensitive and time-consuming and cannot be recommended for routine screening of antigiardial drugs. The radiometric growth assay is therefore a simple, objective measure of antigiardial drug activity which could be used to determine drug sensitivity profiles of clinical isolates or for screening new antigiardial drugs.

Heterogeneity in the responses of clones of Giardia intestinalis to anti-giardial drugs

Clones of two stocks of Giardia intestinalis have been tested by the [ 3H]thymidine uptake assay to determine their sensitivity to metronidazole, tinidazole, furazolidone and quinacrine. Each stock was not homogeneous with respect to drug sensitivity but was composed of different populations of organisms. Doubling times of lines derived from clones of a stock did not vary significantly. These findings may, in part, account for treatment failures in human giardiasis patients.