GIARDIA-DUODENALIS - EXPOSURE TO METRONIDAZOLE INHIBITS COMPETITIVE INTERACTIONS BETWEEN ISOLATES OF THE PARASITE IN-VITRO

The competitive interactions of genetically distinct isolates of Giard ia duodenalis with different growth rates were studied in vitro. Elect rophoretic analysis of mixed cultures showed that competition between 2 cloned isolates occurs under normal in vitro culture conditions, wit h faster-growing isolates outcompeting those with slower growth rates. The addition of sublethal concentrations of metronidazole to clonal m ixtures in vitro prevented the competitive exclusion, which was seen i n normal culture. This apparently occurred because the drug reduced th e growth rate of the faster-growing but not the slower-growing clone.