C.Difficile Observational Study

Inclusion Criteria: 1. Male or female participants ≥ 18 years of age at the time of signing the informed consent 2. Participants in the Monitoring and Discard Stool cohorts with an active treated CDI, defined as meeting all of the following: * Prior to or at diagnosis of C. difficile, either diarrhea, defined as ≥ 3 unformed stools in a 24 hour period, with the stool being measured as Types 5, 6, 7 on the Bristol Stool Scale or evidence of megacolon, or severe ileus. * A positive local stool test results for toxigenic C difficile collected before entry to the study or evidence of pseudomembranes demonstrated by endoscopy or histopathology. For the Monitoring Cohort - positive test result immediately prior to start of or during SOC treatment. For the Discard Stool Cohort - no more than 7 days prior to entry to the study. * Stool test positive for only GDH or PCR and negative for toxin, provided there is observed clinical improvement noted by the Investigator within 5 days of start of SOC treatment, characterized by a reduction in diarrhea , in the the judgement of the Investigator * Receiving SOC therapy for the treatment of CDI at the time of enrollment. 3. Able to complete all study assessments, and to understand and comply with study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative, or equivalent representative as locally defined) based on the assessment of the PI 4. Able to complete the Follow-up period through Day 42 based on the assessment of the PI. 5. If able, signed and dated written informed consent prior to any study specific procedures, including screening evaluations for participants who consent to participate in the Monitoring cohort. Ensure that participants who are considered by the Investigator clinically unable to consent at screening and who are entered into the study by the consent of a legally acceptable representative show evidence of assent, as applicable in accordance with local regulations. 6. Signed and dated written information consent prior to collection and testing of stool samples for participants in the Discard Stool cohort Exclusion Criteria: 1. Employees of AstraZeneca, clinical study site, or any other individuals directly involved with the conduct of the study, or immediate family members of such individuals. Employees of the clinical site or immediate families of these individuals not directly involved in the clinical study will be permitted to participate. 2. Deprived of freedom by an administrative or court order, or in emergency setting, or hospitalized involuntarily 3. Absence of suitable venous access for serum sampling