[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.