|
ISS
820 East 20th Street
Cookeville, TN 38501 USA
931 526 1106
Bob@sproutnet.com
中文版
En espaņol
| |
A simple
method for the direct detection of Salmonella and Escherichia coli O157:H7 from
raw alfalfa sprouts and spent irrigation water using PCR.
J Food Prot. 2005 Nov;68(11):2256-63.
Johnston LM, Elhanafi D, Drake M, Jaykus LA.
Department of Food Science, College of Life Science and Agriculture, North
Carolina State University, Raleigh, North Carolina 27695-7624, USA.
The U.S. Food and Drug Administration recognizes that raw seed sprouts are an
important cause of foodborne disease and is now recommending that either spent
irrigation water or final product be screened for Salmonella and Escherichia
coli O157:H7 as a means of assuring the safety of product intended for
consumption. In an effort to streamline such testing efforts, a simple method to
preconcentrate pathogens from sprouts and spent irrigation water was
investigated to facilitate the direct (without prior cultural enrichment)
detection of pathogens using the PCR technique. Alfalfa sprouts and spent
irrigation water were seeded with Salmonella enterica serovar Typhimurium and E.
coli O157:H7 at 10(-1) to 106 CFU/g or CFU/ml, respectively. Samples were
blended (sprouts only) and then centrifuged at high speed to sediment the total
bacterial population. The precipitate was processed for DNA isolation, PCR
amplification, and amplicon confirmation by Southern hybridization. Mean
pathogen recoveries after centrifugation ranged from 96 to 99% for both
pathogens in both matrices. Using primers targeting the invA gene for Salmonella
Typhimurium and the stx genes of E. coli O157:H7, it was possible to detect both
pathogens in alfalfa sprouts at seeding concentrations as low as 10 CFU/g. PCR
detection limits for both pathogens from spent irrigation water were 10(-1)
CFU/ml, the equivalent of 100 CFU/liter of water. Because spent irrigation water
is constitutionally simple, it is particularly well suited for bacterial
concentration by simple centrifugation steps. In this study, progress was made
toward development of a rapid, inexpensive, and sensitive method for the
detection of sprout-associated pathogens that is relevant to current industrial
practices and needs.
|
