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The physiologic state of Escherichia coli O157:H7 does not affect its detection in two commercial real-time PCR-based tests.
MedLine Citation:
PMID:  23200653     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
Multiplex real-time PCR detection of Escherichia coli O157:H7 is an efficient molecular tool with high sensitivity and specificity for meat safety assurance. The Biocontrol GDS(®) and DuPont Qualicon BAX(®)-RT rapid detection systems are two commercial tests based on real-time PCR amplification with potential applications for quantification of specific E. coli O157:H7 gene targets in enriched meat samples. However, there are arguments surrounding the use of these tests to predict pre-enrichment concentrations of E. coli O157:H7, as well as arguments pertaining to the influence of non-viable cells causing false positive results. The present study attempts to illustrate the effects of different bacterial physiologic states and the presence of non-viable cells on the ability of these systems to accurately measure contamination levels of E. coli O157:H7 in ground beef. While the PCR threshold cycle (C(T)) values of these assays showed a direct correlation with the number of bacteria present in pure cultures, this was not the case for ground beef samples spiked with various levels of injured or healthy cells. Furthermore, comparison of post-enrichment cell densities of bacteria did not correlate with injured or healthy cell numbers inoculated before enrichment process. Ground beef samples spiked with injured or healthy cells at different doses could not be distinguished by C(T) values from either assay. In addition, the contribution of nonviable cells in generating positive real-time PCR signals was investigated using both assays on pre-enriched and post-enriched beef samples, but only if inoculated at levels of 10(6) cells/sample or higher, which are levels not typically seen in ground beef.
Authors:
Rong Wang; John W Schmidt; Terrance M Arthur; Joseph M Bosilevac
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Publication Detail:
Type:  Journal Article     Date:  2012-10-06
Journal Detail:
Title:  Food microbiology     Volume:  33     ISSN:  1095-9998     ISO Abbreviation:  Food Microbiol.     Publication Date:  2013 Apr 
Date Detail:
Created Date:  2012-12-03     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8601127     Medline TA:  Food Microbiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  205-12     Citation Subset:  IM    
Copyright Information:
Published by Elsevier Ltd.
Affiliation:
U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933-0166, USA. Electronic address: rong.wang@ars.usda.gov.
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