Isolate resistance of Blastocystis hominis to metronidazole

Isolates of Blastocystis hominis from infected immigrant workers from Indon esia, Bangladesh and infected individuals from Singapore and Malaysia were assessed for growth pattern and degree of resistance to different concentra tions of metronidazole. Viability of the cells was assessed using eosin-bri lliant cresyl blue which stained viable cells green and nonviable cells red ;The Bangladeshi and Singaporean isolates were non-viable even at the lowes t concentration of metronidazole at 0.01 mg/ml. The parasites of the Malays ian isolate were resistant to a concentration of 0.01 mg/ml, whereas 40% of the initial inoculum of parasires from the Indonesian isolate at day one w ere still viable in cultures with 1.0 mg/ml metronidazole. The study shows: chat isolates of B. hominis of different geographical origin have differen t levels of resistance to metronidazole. The search for more effective drug s to eliminate the parasite appears inevitable, especially since surviving parasites from metronidazol cultures show greater ability to multiply in su bcultures than controls.