Clostridium difficile un nouvel agent zoonotique émergeant? Mise en evidence du potentiel de transmission à l'homme de souches épidemiques de Clostridium difficile par la consommation des denrées alimentaires

Clostridium difficile is a spore-forming anaerobic bacterium recognised as a major human pathogen responsible for pseudomembranous colitis and nosocomial-antibiotic associated diarrhea. Traditionally, hospitals were considered the main reservoirs for infection. However, in the last years the incidence, deaths, complications and costs of C. difficile infection (CDI) have been rising, not only in healthcare facilities, but also within the community. In the community, it has been detected in a growing number of CDI cases in previously healthy individuals without antimicrobial exposure, hospital stay or any other classical risk factors. Furthermore, the disease has been repeatedly described in younger patients, including children. Some hypotheses have been proposed to explain this peak of community cases, the most obvious being that nowadays more attention is given to CDI surveillance. In the last years, diarrhea due to C. difficile disease might have gone undiagnosed, and in many cases went unreported, particularly in the community. Since 2004, severe outbreaks of CDI have been documented increasingly in the United States, Canada and in Europe. These outbreaks have been associated with the emergence of a novel strain, known as PCR-ribotype 027, characterised by higher than usual levels of toxins A and B production, and the presence of a third toxin named CDT or binary toxin. This strain type is also characterised by its resistance to both erythromycin and fluoroquinolones (i.e. moxifloxacin, gatifloxacin and levofloxacin). However, according to the latest hospital surveillance studies in Europe, since 2010 there is a decrease in the incidence rates of PCR-ribotype 027 while other PCR-ribotypes, including PCR-ribotypes 014, 020, 001, 002, 078 and 015 are increasing. Person to person contact is one source proposed for the spread in the community, occurring after visiting hospitalised patients or residents in long-term care facilities. Employees of these health-care settings can also carry spores and contaminate their entourage. The second hypothesis is contamination from the environment, following visits to a potentially contaminated place, such as hospitals or nursing homes. The two most important potential sources of CDI in the community, which have been demonstrated by investigations in the last decade are animals and foods. While C. difficile is also known as enteric pathogen in some food producing and companion animal species, there are several reports describing the presence of the bacterium in the intestinal contents of apparently healthy animals. Moreover, data published recently suggests animals as an important source of human CDI, which can spread disease through environmental contamination, direct or indirect contact, or food contamination, including carcass and meat contamination at slaughter or in the case of crops, through the use of organic animal manure. By definition, zoonoses are infectious diseases that can be transmitted directly or indirectly between animals and humans, through direct contact or close proximity with infected animals, or through the environment. Foodborne zoonotic pathogens are transmitted via the consumption of contaminated food or drink water. The first description of C. difficile in domestic animals and their environments dates from 1974 and possible foodborne transmission was reported for the first time in 1982. However, nowadays the importance of C. difficile as zoonotic disease remains largely unknown. The "One Health" concept is a worldwide strategy, which recognises that the health of humans and animals is connected and also depends on the environment. The present dissertation is a 5 year national study that has investigated the presence of C. difficile in animals and food, from “farm-totable”. The study was also extended to humans resident in a nursing home and in two hospitals in Belgium and in Spain. The characterisation of the isolates obtained has ultimately allowed comparison of the PCR-ribotype distribution in the different European hospitals, as well as with the PCR-ribotype distribution found in animals and foods. This work explores how C. difficile spreads among human patients, animals, foods and the environment to better understand the potential of the bacterium as a zoonotic or foodborne infectious agent.

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