Abstract :
[en] 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.