Hypothesis: the antibody directed against certain antigens of Clostridium difficile would be predict the Clostridium difficile infection.

This study evaluates the weight of immunity by studying patients with Clostridium difficile infection versus controls (each patient is associated with two controls : diarrheal control without Clostridium difficile, and non-diarrheal control with or without Clostridium difficile). Recurrence and the kinetics of immune response following infection Clostridium difficile are studied by following the patients during three months.

There are also building biological samples collections clinically documented: sera, stool and strains.

CASES :

Inclusion criteria of the cases :

• Hospitalized patients with clinical signs of Clostridium Difficile Infection and specific detection in stools of Clostridium Difficile toxins or/and isolating in stools and by digestive biopsy a strain producer of Clostridium Difficile toxins.
• Patients for which a serum prior to the episode of Clostridium Difficile Infection, ideally as far as possible of the episode, but at least 6 days before the day of diagnosis (D0) will be available.
• Patients for which consent has been signed or by their legal representative by default.
• Patients for whom is found Clostridium Difficile Infection in their file surgical and those for whom Clostridium Difficile Infection is the reason for admission will be included in the study but will be subject of a separate analysis, and their witnesses.

Exclusion criteria of the cases :

• Eligible patients for whom Clostridium Difficile Infection has been strongly suspected clinically but for which no microbiological confirmation will have been obtained.
• Eligible patients for whom no previous serum will have been recovered according to the criteria and conditions. The availability of a serum corresponding to the patient's admission is optional and can not be an exclusion criteria.
• Eligible patients (or their legal representatives) who are opposed to the use of their samples, the achieving samples and/or the longitudinal follow-up.
• Eligible patients who underwent plasmapheresis or treated with monoclonal antibodies to toxin A and B or immunoglobulins during the year preceding the episode of Clostridium Difficile Infection.
• Eligible patients but already included in the study for a recent infection with Clostridium Difficile or transferred to a second health facility for the same episode of Clostridium Difficile Infection.
• Eligible patients whose physicians responsible for the management refused participation in the study.
• Protected persons: pregnant women and children under the age of 18.

Secondarily be excluded the following cases:

• Patients for whom no sample has been achieved or retained by the laboratory of Medical Biology who participated in the diagnosis and monitoring of the patient.
• Hospitalized patients at the time of Clostridium Difficile Infection suspicion and diagnostic sample but released or transferred before rendering necessary microbiological results at baseline (J0 or J3).
• Matched control in a case excluded will be excluded.

NON-DIARRHEAL CONTROL : Eligible patients are those who do not have diarrhea at the time of recruitment.

To ensure that exposure to risks similar for cases and controls (hospitalization, usually care epidemic period, ...) will be recruited eligible patients according to the following criteria:

• Within a maximum period of six months after the inclusion of cases.
• Hospitalized in the same hospitalization service type as the case.
• With a duration of prior hospitalization at least as long as the time between admission and the corresponding case J0,
• Matched on sex and three age categories (18-40, 41-60 and> 60 years).

The inclusion of these controls depends on the one hand signing an informed consent for participation in the study and secondly the lack clinical signs suggestive of Clostridium Difficile Infection at the time of inclusion and known history of Clostridium Difficile Infection in their medical records (one no-diarrheal control hospitalized (ND) for one case).