Food Safety

Title: Prevalence and Molecular Epidemiology of Clostridium Difficile in Food and Companion Animals, Retail Meats, and Humans in Minnesota

James Johnson (Infectious Diseases and International Medicine)
Co-Investigators: Stacy Holzbauer (Minnesota Department of Health), Kirk Smith (Minnesota Department of Health), Jeffrey Bender (Veterinary Public Health, Francisco Diez-Gonzalez (Food Science and Nutrition), Megan Shaughnessy (Infectious Diseases and International Medicine), David Boxrud (Minnesota Department of Health)

Amount Awarded: $100,000
Timeframe: March 2011 - March 2013

Abstract: Clostridium difficile (CD) infection (CDI) is an increasingly frequent and severe illness among humans. A growing fraction of CDI cases occurs in the community and involves individuals who lack traditional risk factors for CDI, such as antibiotic use and healthcare exposure. This, plus sporadic reports of recovery of CD from food animals, companion animals, and retail meats, suggests a possible zoonotic or foodborne component to the current CDI epidemic. To gain insights into this possibility, we propose (i) to screen diverse Minnesota food animals and companion animals, plus locally purchased retail meat products, for CD; (ii) to compare prevalence values across animal species and meat types, in relation to production methods, especially antibiotic exposure; and (iii) to molecularly type the isolates, then compare the genotypes of animal-source and food-source isolates with those of human clinical CD isolates from the Minnesota Department of Health's ongoing population-based CD surveillance in central Minnesota. The study's findings will provide novel insights into the possibility of zoonotic or foodborne transmission of CD to humans in Minnesota, and will generate pilot data for a future larger grant application.

Title: Biorational Development of Plant Disease Biocontrol

Linda Kinkel (Plant Pathology)
Co-Investigators: Christine Solomon (Center for Drug Design), Carl Rosen (Soil, Water, and Climate)

Amount Awarded: $100,000 
Timeframe: January 2009 - December 2009

Abstract: Biological control of plant disease offers significant promise as a means for reducing pesticide inputs into the environment and enhancing food safety. However, questions remain about the potential for antibiotic-producing biocontrol organisms to increase the frequency of antibiotic resistance genes in environmental microbes. The acquisition of antibiotic resistance genes by clinically-significant bacteria from environmental microbes represents a substantial public health risk. The proposed work explores strategies to minimize the risk that biological control of plant diseases will contribute significantly to the development of an environmental reservoir of resistance to medically-significant antibiotics. Specifically, this work develops a multiple-strain biocontrol strategy to minimize directional selection for individual antibiotic resistances; uses biochemical analyses to exclude from consideration antagonists that produce clinically relevant antibiotics; and determines the frequency of resistance and the likelihood of the development of resistance by pathogen isolates to different antagonists as a basis for antagonist selection. The proposed work will both enhance the prospects for effective biological control and reduce the likelihood of significant increases in antibiotic resistance genes among the pathogen population in soil. This work will also develop new and interdisciplinary ways of addressing issues at the agricultural-human health interface.

Results: Their work explored strategies to minimize the risk that biological control of plant diseases will contribute significantly to the development of an environmental reservoir of resistance to medically-significant antibiotics.  Specifically, they compared multiple-strain combinations of bacterial antagonists with single strain inoculum formulations as a means for minimizing directional selection for individual antibiotic resistance genes.  These studies also validated their hypothesis that multiple strains are more effective inhibitors of pathogens than any single species alone. Furthermore, they screened a collection of biocontrol strains for their capacity to resist medically relevant antibiotics (vancomycin, tetracycline, erythromycin, chloramphenicol, amoxicillin, and rifamipicin), and for their capacity to produce these antibiotics. Field-scale application should focus only on those antagonistic strains that do not produce or have resistance genes against medically relevant antibiotics. This will help to minimize dissemination and selection of antibiotic resistance genes in the environment, reducing the risk of transferring potential resistance to human pathogens. Finally, their work considered the effects of agricultural management, and specifically nitrogen inputs, on biocontrol effectiveness for individual and multiple-strain inocula. Nitrogen inputs reduced disease suppression in both cases, but multiple strain inoculation produced better disease control than single strain inoculum in the presence and in the absence of nitrogen.  Overall, their work contributes to improved strategies for biological control of plant diseases by utilizing a mixture of microbial antagonist strains and minimizing the risk of transferring antibiotic resistance genes to human pathogens.

Title: Microbial Ecology, Control and Consumer Perception of Foodborne Pathogens Associated with Fresh Vegetables.

Francisco Diez-Gonzalez
Co-Investigators: Jeffrey Bender (VPM, CVM); Craig Hedberg (EHS, SPH); Michael Sadowsky(SWC, CFANS); Cindy Tong (Horticulture, CFANS)

Amount Awarded: $587,005
Timeframe: March 2008 - February 2011

Abstract: Recent food poisoning outbreaks have been caused by eating vegetables contaminated with harmful strains of E. coli andSalmonella. In order to prevent these outbreaks we need a better understanding of how current farm practices lead to or prevent contamination and what unique characteristics of these pathogenic bacteria allow them to survive on vegetables. This project involves microbiologists, horticulturists, and public health and food safety experts working together to identify farm practices, environmental conditions, and specific genes that allow pathogenic E. coli and Salmonella to contaminate and grow on vegetables such as lettuce, spinach, and tomatoes. The project's findings will help us develop effective control measures to reduce the number of food poisoning outbreaks and enhance consumer confidence in the safety of fresh fruits and vegetables.