Escherichia coli O157:H7 Indicator Organism

<p>
Simple, rapid, and accurate tests are desperately needed by beef processors for detection of E. coli O157:H7. Historically, enumeration of various bacterial populations (total aerobic bacteria, Enterobacteriaceae, generic E. coli, etc.) has been used to give an indication of trends in pathogen population, but these tests have not been supported by significant correlation data.
Conversely, tests to evaluate pathogen populations directly, especially E. coli O157:H7, are labor intensive and take multipledays to generate results.</p>
<p>
There are a variety of methods to identify members of diverse bacterial populations. Biochemical assay-based methods have traditionally been used to classify individual strains. These methods are slow and the results are biased towards those strains that are amenable to cultivation in the lab. Molecular-based methods are now being used more frequently and they don't require culturing of the organism prior to identification. </p>
<p>
One such method is denaturing gradient gel electrophoresis (DGGE). DGGE classifies organisms based on the melting profile from amplified segments of target genes. For the purposes of this study, the 16S ribosomal RNA gene will serve as the target gene. The genus and species of several bacteria can be derived based on the unique sequence of the 16 S rRNA gene. The sequences of these genes will be determined without enrichment of the bacterial population, thus, reducing bias towards those strains amenable to in vitro culture. Once candidate strains for indicators of E. coli O157:H7 have been identified by molecular methods, rapid assays for their identification will be developed. Upon successful development of the assays, correlation studies will be carried out to determine the relationship between E. coli O157:H7 prevalence and that of the indicator organism.</p>