ERP Micro December 2019

Green Onion – 25 g Test Portion (Unpaired) Method Comparison Of the 20 low inoculation level replicates of the Assurance® GDS for E . coli O157:H7 Tq assay, by manual processing, there were 5 presumptive positives and 5 confirmed positives following the traditional confirmation procedures. There were 4 confirmed positives for the reference method. Of the 5 high inoculation level replicates, there were 4 presumptive positives and 4 confirmed positives following the traditional confirmation procedures. There were 4 confirmed positives for the reference method. MPN analysis of the inoculation levels determined the concentration of E . coli O157:H7 for the low level was 0.17 MPN/test potion and 2.00 MPN/test potion for the high level. All uninoculated samples were negative. The POD analysis between the GDS EHEC presumptive (POD CP ) and confirmed results (POD CC ) indicated that there was no statistically significant difference at the 5% level for both at the 8 h of enrichment. The POD analysis between the GDS EHEC methods presumptive (POD C ) and reference method confirmed (POD R ) results indicated that there was no statistically significant difference at the 5% level for both methods. Discussion In the internal method comparison study, POD statistical analyses of the samples indicated that for all foods analyzed, there was no statistically significant difference between the EHEC presumptive results compared to the EHEC confirmed. The GDS and the reference culture methods are not statistically different for the detection of E . coli O157:H7 in green onions. The alternative method (enrichment media) recovered statistically better for frozen finely textured beef and on carcass cloths. The mEHEC® broth is more selective compared to the mTSB media. This greater selectivity by mEHEC® may be the reason that the mEHEC® broth recovered more E . coli O157:H7 positive samples compared to the reference method for carcass cloths and finely textured beef.

Minor modification for Sample processing using the PPMX automated system

Results

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