Student Research: John Schultz

MS, , 2006
Faculty Advisor: John Meschke

Pathogen Prevalence and Antibiotic Resistance in Ready-to-Eat Food Products


The consumption of microbiologically contaminated food products in the United States results in a large number of otherwise preventable illnesses and deaths. Monetary losses from food borne diseases are significant and impact the economy in the form of decreased worker productivity and product recalls. Adulteration of food products with pathogenic organisms frequently occurs in the production process or in handling before final preparation. Common food products associated with outbreaks include ground beef, pork, poultry, and certain produce items. Contamination of foods with bacteria may occur through contact with improperly maintained equipment or other controllable handling and processing steps at the final point of purchase. Treatment of infections caused by food borne disease is made more difficult if the pathogen has acquired resistance to commonly prescribed antibiotics. Because second or third choice antibiotics may be required, extended treatment regimes, increased severity of disease or expense, and adverse side effects may result.

The objectives of this study were: 1) To determine the prevalence of the common human pathogens Camplobacter jejuni, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli 0157:H7, and Salmonella species in at-risk foods and 2) To evaluate the number of recovered organisms expressing multi-drug antibiotic resistance using VITEK identification and sensitivity analysis. To address this first objective, bacterial indicators and pathogens were examined using a suite of detection and characterization techniques including 3M Petrifilm plates, multiplex Polymerase Chain Reaction (PCR) assays, latex bead agglutination, immunoassay strips, and traditional culture methods where applicable. Samples included deli meat products, commercially prepackaged meat slices, ground pork and beef portions, poultry products from various suppliers, pre-made sandwiches, and sprouts. The second study objective was achieved by developing a novel antibiotic screening protocol to isolate multi-drug resistant organisms from ground beef, pork, and sprouts. Results of this research indicate that pathogens exist in significant quantities within these food products and that traditional isolation techniques may be significantly underreporting pathogen prevalence in relation to PCR detection sensitivity. In addition, a large proportion of foods sampled harbored multiple-drug resistance microbes and may pose a threat of transmission between pathogen populations impacting typical treatment of disease. These results may serve as an important first step in developing microbiological Hazard Analysis and Critical Control Point (HACCP) programs for food retailers as well as providing information on pathogen prevalence and extent of antibiotic resistance in these foods.