Improvement in isolation and axenic growth of Giardia intestinalis strains

Twenty fresh Giardia intestinalis strains were isolated by inoculation of trophozoites obtained by in vitro excystation procedure or by duodenal aspiration. The strains were continuously cultivated in TP-S-1 or bile-supplemented BI-S-33 media without antibiotics. No correlation was found between the ease of isolation and axenization of Giardia strains and the source of material for inoculum preparation (faeces v. duodenal fluid and symptomatic patients v. asymptomatic cyst passers). Panmede and Trypticase used in TP-S-1 and TYI-S-33 media vary in their ability to support the growth of particular strains. Of the five sera used in TP-S-1 medium no variations were associated with bovine and calf serum. The bile-supplemented BI-S-33 medium supported the growth more consistently than did the TP-S-1 and TYI-S-33 media; depending on the strain, the mean number of trophozoites at 120 hours was 1.1 X 10(6) to 1.8 X 10(6), and the generation times were 8.1 to 16.6 hours.