Question:
The CDC has acknowledged that non-0157 STEC have been an under-estimated threat to public health noting that non-0157 STEC now account for as many illnesses as the 0157 serotype. Are there testing methods available today that identify the non-0157 within reasonably short times for processors with products that have limited shelf-life?
Answer from the Expert (Dr. Olstein):
Several diagnostic methods exist for the identification of the USDA “Big Six” Serotypes and many provide results in shorter times than the USDA method. Most options require at least a 12-24 hour enrichment, followed by multiplex PCR for identification of the virulence genes. Positive samples require isolation steps involving plating on selective differential media and subsequent serotyping.
Paradigm Diagnostics has recently received AOAC approval for its PDX-STEC single medium enrichment for Salmonella and STEC in ground beef. Samples that have been enriched for 6-8 hours (low inoculation levels, < 0.02 CFU/g ) have detectable levels of STEC virulence genes by PCR.
In the absence of PCR, broth samples can be enriched for 12-18 hours and streaked on differential agar plates. Isolated presumptive STEC and Salmonella colonies can be confirmed using qPCR.
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