Rapid Quantitative Method Development for Beef and Pork Lymph Nodes Using BAX^® System Real Time <i>Salmonella</i> Assay

Abstract

The goal of this study was to develop a rapid RT-PCR enumeration method for Salmonella in pork and beef lymph nodes (LNs) utilizing BAX®-System-SalQuant® as well as to assess the performance of the methodology in comparison with existing ones. For study one: PCR curve development, pork, and beef LNs (n = 64) were trimmed, sterilized, pulverized, spiked with 0.00 to 5.00 Log CFU/LN using Salmonella Typhimurium, and then homogenized with BAX-MP media. Samples were incubated at 42 °C and tested at several time points using the BAX®-System-RT-PCR Assay for Salmonella. Cycle-Threshold values from the BAX®-System, for each Salmonella concentration were recorded and utilized for statistical analysis. For study two: Method comparison; additional pork and beef LNs (n = 52) were spiked and enumerated by (1) 3M™EB-Petrifilm™ + XLD-replica plate, (2) BAX®-System-SalQuant®, and (3) MPN. Linear-fit equations for LNs were estimated with recovery times of 6 h and a limit of quantification (LOQ) of 10 CFU/LN. Slopes and intercepts for LNs using BAX®-System-SalQuant® when compared with MPN were not significantly different (p p > 0.05). The results support the capability of BAX®-System-SalQuant® to enumerate Salmonella in pork and beef LNs. This development adds support to the use of PCR-based quantification methodologies for pathogen loads in meat products.

Keywords

• beef lymph nodes
• pork lymph nodes
• <i>Salmonella</i> quantification
• pathogen control