Purpose: The objective of the present study was to validate a new multiplex qPCR screening assay for Y. pestis in meat products compared to cultural isolation procedures.
Methods: Hot dog and meat-based baby food were artificially contaminated with Y. pestis at un-inoculated, low (~1 CFU/g) and high (~10 CFU/g) levels (n = 6/level). Ground beef patties were inoculated at 10-fold greater concentrations based on earlier experimental data. After 24 h enrichment, samples were screened by two different qPCR assays and plated for cultural isolation and recovery. Four additional food matrices (ground beef, ground turkey, raw chicken, and deli meats, 20 sources each) were surveyed by qPCR and culture at one inoculum level (10–400 CFU/g).
Results: Fractional qPCR detection and cultural recovery rates were observed at the low level inoculum for hot dog and baby food (4/6 and 2/6, respectively). Screening of beef patties by qPCR at low levels was positive in all samples and 4/6 by cultural methods. All samples were positive by all methods at the higher level. There was no difference (P < 0.05) between detection rates using either qPCR method or culture. However, in the survey portion of the study, average qPCR detection rates of Y. pestis were 80%, 50%, 33% and 100% from different sources of beef, turkey, chicken and deli meat, respectively, while cultural recovery rates were 0%, 0%, 5% and 55%, respectively.
Significance: Rapid screening of food enrichments by qPCR can provide vital information on potential presence of Y. pestis, especially if background microflora adversely affects cultural isolation and recovery.