Purpose: To compare the ISO method to the VU assay for analysis of rinses of raw poultry, with respect to agreement (equivalence?), as well as cost and time benefits.
Methods: The ISO method was compared to the AOAC-approved VU protocol. The latter was also modified by inclusion of a 2-4 or 12 h pre-enrichment as well as, post-assay, selective enrichment using RVS medium or immunoconcentration (VIDAS ICS protocol), prior to plating to SMID agar. All protocols were tested using 90 raw poultry samples. All data points were analyzed statistically. A time and motion was performed for each of the assays using a stopwatch and 30 samples.
Results: There was disagreement between the two analytical methods when used without modification, due to overgrowth by the background flora upon plating for confirmation. Reliable detection of Salmonella from raw poultry required a minimum of a 2 h pre-incubation prior to addition of the VU selective supplement. Following the UP protocol, selective enrichment using RVS medium or the VIDAS ICS was required to reduce breakthrough organisms such as E. coli, Citrobacter and Klebsiella spp. Likely due to low numbers and random distribution, 100% agreement between methods is unlikely. The VU method was more efficient with respect to labour (75% reduction), materials (25% cost reduction), and lead time (40-67% reduction).
Significance: The modified VU assay provides efficiencies in laboratory operation and timely results when monitoring CCPs in poultry processing.