[Effect of different drugs on Echinococcus multilocularis metacestodes in vitro ].

Objective: To test the effect of 6 drugs or combination on the in vitro cultured Echinococcus multilocularis (Em) metacestodes.

Methods: The drugs used included albendazole (ABZ), itraconazole (ITZ), ivermectin, miltefosine, nitazoxanide (NTZ), and rifampin. The Em metacestodes were cultured for 5 weeks and divided into 17 groups each with 120-140 cysts: ABZ groups (1 microg/ml and 10 microg/ml), ITZ group (0.7 mg/ml), ivermectin group (1.75 mg/ml), miltefosine groups(0.5 microg/ml, 2.5 microg/ml and 7.5 microg/ml), NTZ groups (0.1 microg/ml, 1 microg/ml and 10 microg/ml) and rifampin group (10 microg/ml); groups of NTZ combined with ABZ at respective concentration (10 microg/ml + 10 microg/ml, 10 microg/ml + 1 microg/ml, 1 microg/ml + 10 microg/ml, 1 Igg/ml + 1 microg/ml); and 2 groups of control: (1) experiment culture containing 40 microl of dimethyl sulfoxide (DMSO) per 20 ml and (2) blank culture medium. In the 6 weeks culture period, the drug effect on the Em cysts was observed. Drug combination groups were continually observed for 3 weeks, 3 months and 6 months after discontinuation of drugs. In order to determine the viability of metacestodes, the cysts were injected intraperitoneally into female BALB/c mice, and 8 weeks later, the mice were sacrificed for collecting the parasites.

Results: Ivermectin, miltefosine and rifampin showed no effect on metacestodes. Albendazole, itraconazole, nitazoxanide and albendazole combined with nitazoxanide all inhibited or killed the parasites in the in vitro culture system (P < 0.05). High dose of nitazoxanide (10 microg/ml) was more effective in the destroying parasites than others. No regrowth of cysts was observed in the 4 groups of combination treatment with nitazoxanide and albendazole continually cultured for 3 weeks, 3 months, or 6 months after drug discontinuation. In the in vivo viability test, no metacestodes were found in all mice in the nitazoxanide group (10 microg/ml) and 2 mice in albendazole group, but the parasites developed in all mice at 8 weeks after injection in other single drug groups. Also, no metacestodes from all the combination treatment groups were found re-developed in mice.

Conclusion: This investigation indicates certain inhibitory effect of itraconazole and nitazoxanide on Em cysts, and a combination of albendazole with nitazoxanide may enhance the parasitocidal effect.