“…A few strains with the designation 'decreased sensitivity' to metronidazole were isolated from Danish patients in whom treatment had failed (Nielsen, 1973), but the overall susceptibility of these strains did not differ from the normal distribution found by us and by others in a series of patients with T. vaginalis (0degaard, 1962;Schropl and Rockl, 1963). In view of these findings we are inclined to rule out in vitro resistance to metronidazole (or tinidazole) as the cause of the therapeutic failures which may be encountered.…”