Food Protection Trends - July 2008 - (Page 468)

ARTICLES Copyright© 2008, International Association for Food Protection 6200 Aurora Ave., Suite 200W, Des Moines, IA 50322-2864 Food Protection Trends, Vol. 28, No. 7, Pages 468–472 An Integrated Assay for Rapid Detection of Escherichia coli O157:H7 on Beef Samples JOHN WILLFORD1 and LAWRENCE D. GOODRIDGE2 * 1 Dept. of Animal Science, University of Wyoming, Laramie, WY 82071, USA; 2Dept. of Animal Sciences, Colorado State University, 350 West Pitkin St., Fort Collins, CO 80523-1171, USA SUMMARy INTRODUCTION Escherichia coli O157:H7 continues to be an important agent of foodborne illness, causing an estimated 70,000 illnesses, 2,000 hospitalizations, and 60 deaths annually in the United States (9). Fecally contaminated food and water are the sources of E. coli O157:H7 infections in humans (4). Cattle and other ruminants have been established as natural reservoirs for E. coli O157:H7, and these food production animals continue to play a role in the epidemiology of human infections (7). During 2007, there was a spike in E. coli O157:H7-related beef recalls. For example, approximately 30.1 million pounds of ground beef were recalled, and the implicated ground beef collectively resulted in at least 55 cases of E. coli O157:H7 illness (3). It is clear that there remains an acute need for the development of easy-to-use, robust, and sensitive detection methods for this pathogen. Also, although many methods have been developed to detect E. coli O157:H7 in food and water, most of the tests are not designed to be conducted in a field setting. The plethora of diagnostic methods that have been developed for detection of this organism The Phast Swab is a vertically integrated assay for rapid detection of Escherichia coli O157:H7. A sampling device, an E. coli O157:H7 reporter bacteriophage carrying the lacZ gene, bacterial growth medium, E. coli O157:H7-specific immunomagnetic beads and a β-galactosidase substrate (colorimetric or luminescent) are contained within a Snap Valve™ device. To conduct the assay, a sample to be tested is swabbed, and the swab is returned to the Snap Valve™ device; an eight-hour enrichment follows. Any E. coli O157:H7 cells are isolated and concentrated by immunomagnetic separation, and the reporter bacteriophage is added to the test compartment, where it infects any viable E. coli O157:H7 present in the sample, forcing the bacteria to make large amounts of β-galactosidase. Following the infection process (approximately 1 h), the cap of the Phast Swab is broken, releasing the substrate, which reacts with the β-galactosidase to produce a colorimetric signal (read visually) or a luminescent signal (read with a hand-held luminometer). The Phast Swab was evaluated for its ability to detect E. coli O157:H7 on 100 cm2 portions of beef. The assay was capable of detecting 103 CFU/100 cm2 of E. coli O157:H7 within 12 hours when a colorimetric substrate was used, and 101 CFU/100 cm2 within 10 hours with the use of a luminescent substrate. The nature of this detection method is such that it effectively detects E. coli O157:H7 in a simple and rapid manner, with minimal need for instrumentation to interpret the test result. A peer-reviewed article *Author for correspondence: 970.491.6271; Fax: 970.491.5326 Email: Lawrence.Goodridge@Colostate.edu 468 FOOD PROTECTION TRENDS | JULY 2008

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Food Protection Trends - July 2008 Contents Sustaining Members Lone Star Perspective from Your President Commentary from the Executive Director An Integrated Assay for Rapid Detection of Escherichia coli O157:H7 on Beef Samples Listeria Prevention Practices for Small Cheese Operations New Members News Industry Products Award Winners Committee Meetings Ivan Parkin Lecture John H. Silliker Lecture Preliminary Program Networking Opportunities General Information Registration Form Workshops Exhibitors Special Contributors and Sponsors Coming Events Advertising Index Journal of Food Protection Table of Contents Audiovisual Library Order Form Booklet Order Form Membership Application

Food Protection Trends - July 2008

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