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WVDL Testing Improvements to Salmonella Dublin PCR

Salmonella Dublin real-time PCR testing improvements at WVDL

 

Upon examination of the gene target for the Salmonella enterica subspecies enterica serotype Dublin real-time PCR, the WVDL discovered that the gene can now be harbored in E. coli.  From the literature, it appears that the gene may have been recently (<6 mo.) taken up by E. coli.  At this time, the WVDL does not know the prevalence of this gene in coliform bacteria identified in fecal and tissue samples.  Our case load analysis suggests that it is low (3-6% of tests on fecal and tissue samples per year).  Currently, we have identified only a single E. coli isolate carrying this gene, but we are performing additional analysis to determine if more E. coli harbor this target gene.

Because Salmonella ser. Dublin diagnosis on a farm has a high consequence, we want to be 100% sure that the PCR test is indeed detecting Salmonella ser. Dublin and NOT detecting an E. coli or other coliform bacteriaTherefore, effective 6/27/2018, the WVDL will NOT report presumed positive Salmonella ser. Dublin real-time PCR results without confirmatory testing with conventional PCR.  Negative Salmonella ser. Dublin results will be reported, as this observation does not affect negative results.  All presumed positive real-time PCR results will be confirmed using a confirmatory test and both results reported.  Preliminary results will be reported and, as always, available 24/7 on our client portal on our website:  www.wvdl.wisc.edu.

Our goal is to have the confirmatory conventional PCR test validated in July of 2018.  Presumed positive Salmonella ser. Dublin PCR results will remain pending until the confirmatory testing is completed. Once the conventional PCR is validated, the additional testing will likely cause a 24-48 hour delay on Salmonella ser. Dublin PCR results until a new real-time Salmonella ser. Dublin PCR assay is adapted.  We anticipate this process to take 2-3 months.

We apologize for the delay and any inconvenience this may create for you and your clients.  We appreciate your business and continued patronage as we work to improve this test.  If you have any questions, please see our website or contact us at any time.