Prevalence of Clostridium difficle (C. diff) in Connecticut Swine farms
There is a growing concern over the antibiotic-induced emergence of bacteria such as Clostridium difficle in livestock and its implication for public health. C. difficle (C. diff) is the main cause of antibiotic induced diarrhea acquired in hospital settings. Recently, infection has not only been seen in individuals with no hospital contact – referred to as Community acquired Clostridium difficle associated diarrhea (CA-CDAD) – but infections have also increased in severity. This study proposes to determine if the farm environment is a potential source of infection by looking at colonization rates for C. diff in CT swine industry. This involves collecting and testing animal fecal materials on 20 breeding farms, and comparing strains isolated to human strains circulating in the region.
This study is currently in its first quarter (Sept-Dec); it has been successfully incorporated into an existing study looking at MRSA on pig farms. The CT Department of Public Health has agreed to include fecal sampling in its annual testing protocol. All necessary Yale human and animal review board approvals have been obtained. In November, the lab clearance for C.diff culture and isolation was granted by the Yale Environmental Safety office. Survey instruments, sampling and lab protocol, have been drafted and will be tested by Jan 2011. A lab willing to conduct molecular typing has been identified. Twenty farms that participated in MRSA study are willing to participate in this study. Annual testing of CT breeding swine farms usually begins in early spring (Feb) and ends in summer (July). Thus, sample collection for this study will be done within this same period.
Study Objective 1. To determine the prevalence of C.difficle in CT swine breeding farms two main components must be fulfilled: farm sampling and laboratory analysis. These areas are addressed below.
A. Farm sampling: As noted earlier, an ongoing study on MRSA in CT pig farms funded by 2 year NIH training grant have been expanded to include this study. The CT Department of Public Health is mandated to test all breeding farms for brucellosis annually, and the student currently accompanies the state inspectors on their farm visits with farmers` prior consent. Under the existing study nasal swabs have been collected from pigs; for C. diff, sampling, this has been expanded to include pig fecal collection. The second phase for MRSA testing begins Feb 2011.
B. Laboratory Analysis: Also to achieve objective 1, established analysis will be conducted to isolate C. difficle from samples collected on farm. A BL2 lab is available at the Yale School of Public Health for this project; this lab is currently being used for the MRSA study, and it has been approved for the isolation of C. difficle. Due to the labor and cost involved in culturing C.diff, a real time PCR assay is being developed to detect C. diff toxins (TcdA and TcdB) in pig feces. If toxins are present positive samples will then be cultured and further molecular testing will be done. A lab technician with competency in both microbiology and molecular methods is currently being recruited on a part times basis to assist in developing this assay.
Study Objective 2. Using established molecular methods, compare the strain of C. difficle in farms to existing strains circulating in the human population in the region and also porcine isolates in other regions of the country so as to give a broader picture on the disease burden.
To enable such comparison, PCR will be used to determine the strain of any and all farm isolates. Of specific interest is to determine the presence of PCR ribotypes 027 and 078, which have been linked to both animal and human CA-CDAD outbreaks and are known to be hyper-virulent. Established PCR ribotype protocols have been published and will be used to type farm isolates.
Also Pulse-Field Gel Electrophoresis (PFGE) is the gold standard used in the US to type C. diff so this method will be employed. PFGE is already being used in typing MRSA; this protocol has been expanded to include C.diff. As mentioned earlier the lab processing the MRSA isolates has agreed to type C.difficle. Thus, C.diff positive isolates will be sent to the participating lab for PFGE typing.
Study Objective 3. Conduct a Knowledge, Attitude and Belief (KAB) survey regarding bio-safety practices.
As part of the MRSA study, the student is working with UConn swine veterinarian at the University of Connecticut (UCONN) and an occupational health group at Yale with an interest in farmers` health. In consultation with these experts and a statistician (as advised by the grant reviewers) a questionnaire is being developed looking at bio-safety practices on farm. This questionnaire is currently being piloted on a sample of farmers.
- -This study is in its first quarter; all necessary approvals have been obtained. -Study has been successfully incorporated into existing MRSA study. -All 20 farms have been identified for sampling and fieldwork will begin in early spring. -A lab technician has been identified with over 10 years of experience and is currently being recruited. -All study protocols has been drafted. -Three farms have agreed to be used to test sampling and lab protocols.
Impacts and Contributions/Outcomes
Impacts and Contributions/Outcomes
In 2006 CDC published a study using data collected from CT physicians showing that a quarter of patients presenting with gastroenteritis symptoms were otherwise healthy individuals with no known risk factors, thereby signifying infection sources within the community. Thus, this study proposes to determine if the farm environment is a potential source of infection by looking at colonization rates for C. diff in CT swine industry. This involves collecting and testing animal fecal materials on 20 breeding farms, and comparing strains isolated to human strains circulating in the region.
Also the Department of Public Health is currently testing animal products (pork and beef) for C.difficle; results from this study will complement this ongoing effort thereby narrowing the existing knowledge gap regarding the scope of C.diff infection. In addition, this study demonstrates the feasibility of farm screening as a surveillance tool in emerging infectious disease since 70% of these are zoonotic.
Professor of Epidemiology of Microbial Diseases
Yale University School of Public Health
60 College Street
New Haven, CT 06520
Office Phone: 2037856732