Q: 28 year old female with 22 weeks of gestation is admitted to ICU with dehydration secondary to severe diarrhea. Patient has massive leucocytosis with abdominal pain. Patient was recently treated with antibiotics as out-patient  for her community acquired pneumonia. You want to cover her against C.diff. colitis. What would be the preferred agent?

Answer: Oral Vancomycin

Oral vancomycin is preferred over oral metronidazole for severe C.Diff. colitis anyway. Metronidazole has the potential to cause birth defects so during gestation oral vancomycin is preferred over metronidazole.

Reference:

Surawicz, Christina M; Brandt, Lawrence J; Binion, David G; Ananthakrishnan, Ashwin N; Curry, Scott R; Gilligan, Peter H; McFarland, Lynne V; Mellow, Mark et al. (26 February 2013). "Guidelines for Diagnosis, Treatment, and Prevention of Clostridium difficile Infections". The American Journal of Gastroenterology 108 (4): 478–498