Purpose: To compare results using Universal Pre-enrichment Broth (UPB) and Lactose Broth (LB) enrichment media for testing whey protein powder with the Atlas Salmonella Detection assay and confirmation via by culture methods.
Methods: Whey protein powder samples were inoculated at 100 CFU/25g and 200 CFU/25g of Salmonella Typhimurium. The samples were stored for 2 weeks at room temperature followed by a 24 h enrichment in Universal Pre-enrichment broth (UPB) at 42°C or Lactose Broth (LB) at 35°C. After enrichment, sample processing included purification via Target Capture, amplification by Transcription Mediated Amplification, and detection by Hybridization Protection Assay. Culture confirmation was performed by transferring 1000 µl of enrichment to 10 ml of Tetrathionate Broth for 24h at 35°C and streaking onto ChromAgar Salmonella and XLD.
Results: In a one to one comparison of UPB and LB broths used for sample enrichment, the UPB broth yielded better growth of Salmonella from whey protein powder samples. At the 200 CFU/25g inoculation level, the testing showed 100% (10/10) correlation between the UPB enrichment protocol and culture results and an 80% (8/10) correlation between the LB enrichment protocol and culture results. At the 100 CFU/25g inoculation level, the testing showed 100% (10/10) correlation between the UPB enrichment protocol and culture results and a 30% (3/10) correlation between the LB enrichment protocol and culture results.
Significance: This study demonstrates that at two inoculation levels in whey protein powder, enrichment with UPB at 42°C shows better growth of Salmonella compared to LB enrichment at 35°C after 24 hours of incubation.