Purpose: The study presented shows an accelerated, validated method for screening and isolation of STEC as alternative to the USDA FSIS reference method MLG 5.04.
Methods: Beef trim (n=60) and ground beef (n=60) samples with 375 g weight were artificially spiked with approximately 0.7 CFU/sample cold-stressed E. coli O157:H7. The enrichment extended for 8 hours (beef trims), respectively, 10 hours (ground beef) in RapidCult™ E. coli Enrichment broth and was used for screening with Foodproof® E. coli O157 Detection Kit in Real Time (RT)-PCR and also Lateral Flow based via Singlepath® E. coliO157. Following Immunomagnetic Separation, the identification of suspect colonies on CT-SMAC agar was performed by RT-PCR, Singlepath® test system and examination of Shiga toxin production with Duopath® Verotoxins.
Results: Without any false negative results, the method showed a sensitivity of 100 %; the specificity varied by 70-100 % depending on method cascade and matrix. The new enrichment method enables a screening of 375 g (pooled) samples with results within 14 hours and a completed confirmation already after 3 days. Additional data show the detectability of other monitored STEC such as O111, O26, O103, O145, O45 and O121 from 25 g samples of ground beef after only 8 h incubation time.
Significance: The results demonstrate an alternative method to the MLG protocols allowing a faster E. coli O157:H7 and STEC screening for improvement of food safety. In addition, this method can also be used for the detection of other STEC from ground beef.