A Study to Investigate the Safety and Efficacy of Fidaxomicin (Oral Suspension or Tablets) and Vancomycin (Oral Liquid or Capsules) in Pediatric Subjects With Clostridium Difficile-associated Diarrhea (CDAD)

Inclusion Criteria:

- Subject is diagnosed with CDAD according to local diagnostic criteria. As a minimum
there must be positive detection, within 72 hours prior to randomization, of either
toxin A and/or toxin B in stool or positive detection of toxigenic C. difficile in
stool and:

- Subject from Birth to < 2 years: watery diarrhea in the 24 hours prior to
screening.

- Subject ≥ 2 years to < 18 years: ≥ 3 unformed bowel movements in the 24 hours
prior to screening.

- Male and female subjects aged from birth to < 18 years: Note that in the United
States of America subjects can only be included if aged ≥ 6 months to < 18 years.

- For subjects < 5 years: Negative rotavirus test.

- Female subject of childbearing potential:

- must have a negative urine pregnancy test at Screening, and

- must abstain from sexual activity for the duration of the study, or

- must use two forms of birth control (at least one of which must be a barrier
method) starting at Screening and throughout the study period and for 28 days
after the final study drug administration.

- Female subject must not be breastfeeding at Screening or during the study period, and
for 28 days after the final study drug administration.

- Female subject must not donate ova starting at Screening and throughout the study
period, and for 28 days after the final study drug administration.

- Subject agrees not to participate in another interventional study while in the study
(with the exception of studies as described in exclusion criteria below).

Exclusion Criteria:

- Concurrent use of metronidazole, oral vancomycin or any other antibiotic treatments
for CDAD. If the investigator feels the clinical imperative is to begin treatment
before knowing the laboratory result for toxigenic C. difficile, up to four doses but
no more than 24 hours of treatment with metronidazole, oral vancomycin or any other
effective treatment for CDAD are allowed.

- Subject has pseudomembranous colitis, fulminant colitis, toxic megacolon or ileus.

- Subject has a history of inflammatory bowel disease (e.g., ulcerative colitis or
Crohn's disease etc.).

- Subject has diarrhea caused by an agent other than C. difficile (e.g. infections,
infestations, drugs etc.).

- Subject has known hypersensitivity to fidaxomicin, vancomycin or their excipients or
to teicoplanin.

- Subject has received an investigational therapy within 28 days, prior to Screening,
with the exception of studies with primary treatment for cancer without novel
Investigational Medicinal Product (IMP) and which do not affect the assessment of
diarrhea.