NSERC – Foodborne pathogen-control strategies in pork
Foodborne pathogen-control strategies in pork
Context of the study: procedures against foodborne pathogens are focused in pig slaughter and meat processing, under the application of HACCP standards. However, it turns out that the animals status at slaughter entry is very crucial in order to identify the risk of meat contamination with pathogens, and which have been particularly well established in the case of Salmonella. According to the World Health Organization (WHO), the major emerging pathogens are Salmonella spp., Campylobacter spp., E. coli shigatoxinogenic (or verotoxinogenic), Methicillin-resistant Staphylococcus aureus (MRSA) and Cryptosporidium parvum and some viruses such as hepatitis E virus and Norwalk. At the national level and for a few years, meat safety programs were created and applied in industry. These programs, based on HACCP standards, are dependent on the control of biological, chemical and physical hazards at the farm. Despite the effectiveness of such programs, some hazards still remain thus our research program will focus on reducing this risk to the lowest level.
Research proposal : This program is dedicated to the control of the main zoonotic pathogens in pigs, especially the characterization and epidemiological surveillance of pathogens. It includes two parts:
- 1) phenotypic and genotypic characterization methods of Methicillin-resistant Staphyloccocus aureus (MRSA) in pigs and comparison with human strains; and
- 2) control of Salmonella in breeding farms, and improving swine health. Thus, various control strategies including the use of alternatives to antibiotics and vaccination, will be developed and validated.
1- Comparison of phenotypic and genotypic characterization methods of Methicillin-resistant Staphyloccocus aureus (MRSA) in pigs and comparison with human strains
Context of the study : Porcine MRSA are going to become a major worldwide public health problem. In different countries, MRSA have emerged in humans, in form of invasive skin infections. These MRSA strains, acquired in the community, are called “community-acquired MRSA”. In this context, the colonization and infections due to MRSA in domestic animals become of particular interest; the question that arises here is the possible dissemination between animals and humans.
Currently, the nature and frequency of MRSA strains found on skin abscess and nasal cavities in pigs, at both farms and slaughterhouses, are not documented in Canada. During the slaughter of MRSA-positive animals, the contamination of carcasses and environment can occur and contaminate the meat products, a risk that we propose to evaluate.
Research proposal : Our approach will be to analyze the prevalence of MRSA and to characterize isolats found in pigs at farms and slaughterhouses and compare their genotypic profiles to human isolats. The ultimate objective is to assess the risk associate with MRSA strains found in pigs (for example, at the abscess areas), that can contaminate meat and became an important public health concern.
2- Control of Salmonella in breeding farms, and improving swine health
Context of the study :
Recently, the Canadian pork industry has been facing an increase of Salmonella prevalence in commercial herds, with an estimated infection rate of 40 %. An additional complication, is the emergence of antimicrobial resistance in some strains as Typhimurium DT 104. This serotype found in pigs is one of the most globally identified serovars in cases of human Salmonella infections, especially associated with severe cases of necrotic colitis.
Since 1999, RCMS researchers have focused their efforts on understanding the epidemiology and control of Salmonella, including at the farm level. The analysis of Salmonella contamination sources at Canadian farms reveals that incoming animals are an important source of new serotype introduction, including septicemic strains. It was determined, via a genetic characterization of micro-organisms, that the control and screening of breeding animals is crucial to avoid the introduction of new serotypes within an integrated production. This approach is part of the research program.
In addition, and to avoid that contaminated animals carry the bacterium at the time of slaughter, it is necessary to effectively fight this pathogen at the farm, not only by the implementation of good production practices including biosecurity, but also by the development of specific control strategies.
The use of alternative strategies, i.e., natural products (essential oils, organic acids), against Salmonella and other pathogens on farms, is a necessity in the context of antibiotic withdrawal, as growth promoters in breeding. Beyond the control of Salmonella, the evaluation of alternatives antibiotics will include the assessment of their impact foodborne pathogens and on the intestinal ecosystem equilibrium.
In addition, a subunit vaccine based on biodegradable microspheres has been developed by the RCMS team and demonstrated to be effective in reducing clinical signs associated with salmonellosis in pigs. Further studies are planned as part of the research program due to potential clinical applications of the vaccine, simple administration (oral) and interesting characteristics such as a lack of toxicity and is safe for immunization.
Research proposal : the project will focus on: (a) the identification of introduction sources of Salmonella at selected breeding farms and periodic monitoring of negative -tested sows and piglets (at 3 Canadian provinces) and (b) evaluation of alternatives to antibiotics: (1) food additives such as a combination of organic acids and essential oils, or egg powder; use of textured feed(Mash feed); 3) Passive immunization with egg powder containing antibodies against various pathogens; 4) active immunization with a multivalent subunit vaccine (against Salmonella and S. suis).