Application of a commercial Salmonella real-time polymerase chain reaction (PCR) assay for the detection and quantitation of Salmonellaenterica in poultry ceca

Abstract

Foodborne Salmonellosis is commonly associated with poultry and poultry products necessitating continued development of pre- and post-harvest food safety interventions and risk management strategies. Evaluating technologies and strategies is limited by availability of cost-effective, rapid laboratory methods. The objective of this work was to evaluate a commercial, qualitative PCR assay and its novel quantitative application to detect and enumerate Salmonella in poultry ceca as an analytical matrix. Ceca were collected at harvest, contents homogenized, and paired samples evaluated with Buffered Peptone Water (BPW) and BAX® MP + Supplement (MPS) pre-enrichment broths followed by PCR screening on BAX® System Q7 (PCR) and by isolation. Additional ceca were inoculated with Salmonella to develop a standard curve for the BAX® System SalQuant™ quantitative PCR application (QA), then estimates were obtained by the QA and Most Probable Number (MPN) methods. For pre-enrichment media, PCR outcomes performed equivalently to culture isolation for detecting Salmonella in ceca with 95.65% and 87.88% sensitivity and 82.00% and 100.00% specificity (P=0.074) for BPW and MPS, respectively. However, at the sample-level, BPW performed significantly worse (47.92%) than MPS (68.75%) for overall isolation of Salmonella (P<0.0001). Post-standard curve development, the mean QA estimates obtained for the inoculated samples were 1.14 (95% CI; 0.62 - 1.66), 1.79 (95% CI; 1.50- 2.08), 2.91 (95% CI; 2.65 - 3.17) and 3.76 (95% CI; 3.26 - 4.25), respectively for each targeted inoculation of 1.0, 2.0, 3.0 and 4.0 Log10 CFU/mL and within or comparable to 95% confidence intervals of paired MPN estimates. These data demonstrate performance of MPS for the detection and isolation of Salmonella enterica from poultry ceca when screening with PCR and indicate the QA may be useful as an alternative tool to estimate Salmonella concentrations in ceca, which may support pre-harvest food safety activities.