Evaluation of the Immune Response to Clostridium Difficile in Adults With Clostridium Difficile Infection (CDI)

Patients with an initial episode of CDI will be followed up for CDI recurrence or sustained
clinical response. The subjects will be allocated into 2 groups at the study end:

- Recurrence Group: Subjects who experience recurrence of CDI after clinical response to
antibiotic treatment to treat the initial CDI episode.

- Sustained response Group: Subjects who do not experience recurrence of CDI after
clinical response to the antibiotic treatment to treat the initial CDI episode.

This protocol has been amended twice to improve recruitment of subjects in the study.

Inclusion Criteria:

- Subjects who the investigator believes that they can and will comply with the
requirements of the protocol or/ and subjects who can receive assistance from his/
her legally acceptable representative (LAR) or a designate who can and will comply
with the requirements of the protocol.

- A male or female aged 18 years or older at the time of enrolment.

- Written informed consent obtained from the subject/ LAR of the subject.

- A reasonable prognosis of survival during the study period as judged by the
investigator.

- Outpatients, emergency room and/ or hospitalized subjects diagnosed with CDI for
which the symptoms started maximum 14 days prior to study enrolment.

- Subjects who receive or plan to receive antibiotic treatment to treat the CDI
episode.

Exclusion Criteria:

- Concurrently participating or planning to participate in another clinical study, at
any time during the study period, in which the subject has been or will be exposed to
an investigational or a non-investigational product.

- Previous CDI episode within the previous 6 months before study enrolment (except for
up to ~25% of the subjects).

- Chronic diarrheal illness such as, but not limited to, ulcerative colitis or Crohn's
disease.

- Planned surgery for CDI within 24 hours after study entry.

- Previous vaccination against Clostridium difficile.

- Having received a Clostridium difficile monoclonal antibody product(s) within the
previous 3 months or planned administration during the study period.

- Administration of immunoglobulins within the previous 3 months or planned
administration during the study period.

- Subject having any other condition that, in the opinion of the investigator, would
jeopardize the safety or rights of the subject participating in the study, would make
it unlikely for the subject to complete the study, or would confound the results of
the study.

- Chronic administration (defined as more than 14 days in total) of immunosuppressants
or other immune-modifying drugs within the previous 6 months.

- Any confirmed or suspected immunosuppressive or immunodeficient condition, based on
medical history.

- Family history of congenital or hereditary immunodeficiency.

- Major congenital defects.