Linda Benedict, Morgan, Johnny W.
Marlene Janes, Beilei Ge and Witoon Prinyawiwatkul
Food safety is of paramount public health concern and a focus of research in the Department of Food Science. Food scientists are finding ways to prevent food-related illnesses, which include quick and inexpensive methods for screening and detecting the presence of pathogenic bacteria in food. A number of innovations using new analytical techniques are rapidly evolving.
LSU AgCenter food scientists have developed rapid antibody-based methods for enumeration and detection of Vibrio parahaemolyticus and Vibrio vulnificus in seafood products.
In the United States, seafood is the food category causing the highest number of foodborne outbreaks. A majority of human infections caused by seafood are due to the consumption of raw or undercooked bivalve molluscan shellfish contaminated with vibrios. Gulf Coast oysters are being scrutinized for the presence and level of Vibrio vulnificus and Vibrio parahaemolyticus that are ubiquitous in the marine environment. Research efforts are in progress to develop technologies to eliminate or greatly reduce these pathogens in oysters. To complement these efforts and permit investigators to assess their endeavors, AgCenter food scientists have developed anti-flagellar core antibodies, which are reliable for detection and enumeration of V. vulnificus and V. parahaemolyticus in oysters and seawater.
A leading biotechnology company, bioMérieux, is interested in licensing the antibodies for V. vulnificus and V. parahaemolyticus. The company is testing the antibodies in their VIDAS system, which is a rapid test that detects multiple species-specific antigens. More than 2,000 food laboratories have chosen the VIDAS system for routine analyses of foodborne pathogens.
Traditional detection methods for foodborne pathogens are based primarily on microbiological culturing of the bacteria using enrichment and selective media followed by species identification and confirmation with biochemical tests, such as the ability to ferment sugars. Such processes are labor intensive and time consuming. Molecular-based DNA amplification techniques, primarily polymerase chain reaction (PCR) and recently real-time PCR, have been described for the rapid and sensitive detection of foodborne pathogens without having to culture them first. The main concern associated with these assays is the expensive thermal cycling instrument required by the technique. In the case of real-time PCR, the initial equipment setup can be more than $30,000. This is a significant cost for both regulatory agencies and the food industry. Additionally, an inherent limitation of DNA-based molecular detection assays is the inability to differentiate live and dead cells.
LSU AgCenter scientists have developed a technique for using loopmediated isothermal amplification (LAMP), a novel and rapid molecular method based on DNA amplification technology, to accurately detect major foodborne pathogens of significant food safety and public health concerns. The LAMP assays are rapid (faster than realtime PCR), specific, sensitive and costeffective. Additionally, the LAMP assays do not require sophisticated and expensive instruments such as a PCR thermal cycler. Final results can be obtained in a matter of a few hours. AgCenter scientists used this technique to detect virulent-type Vibrio vulnificus, viable Salmonella cells, and seven adulterant Shiga toxin-producing E. coli (STEC). In the Salmonella assay, propidium monoazide was used to differentiate live and dead cells and found to be specific for viable cells. This addresses the problem of false-positive results commonly associated with molecular detection assays. Three new inventions have been disclosed and filed, one for each pathogen group. A provisional patent has been filed for the set of LAMP assays to detect the adulterant STEC groups. A company in France – Flexx Innovation, Technology Assessment Group – is interested in licensing the LAMP method for Salmonella detection.
Because of the importance of the pathogens involved in foodborne illnesses, the rapid, accurate and cost-effective methods invented at the AgCenter offer reliable tools for the food industry and regulatory agencies to better control potential microbial hazards in the food supply.
Marlene Janes is a professor and Witoon Prinyawiwatkul is Horace J. Davis Professor in Food Technology in the Department of Food Science. Beilei Ge is a former professor in the department and now with Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Md.
(This article was published in the fall 2012 issue of Louisiana Agriculture magazine.)