Q2:
D. Her infection is refractory to a single-dose therapy.

Occasionally, patient will fail to respond to metronidazole therapy 2g orally (once). Since this dose of metronidazole makes most people nauseated, some may vomit after taken this treatment. This could be one cause of failed or inadequate treated. An alternative is to give metronidazole 500mg twice a day for 7 days in this situation. Remember that patients taking metronidazole must refrain from using any alcohol, since the combination of this antibiotic and alcohol will predictably induce vomiting.