Comparison of Neutralizing Buffered Peptone Water and Dey/Engley Broth in the Recovery of Salmonella Enterica from Broiler Carcass Rinsates

Introduction:  Recently, Food Safety and Inspection Services (FSIS) developed new neutralizing buffered peptone water (nBPW) to replace current buffered peptone water for poultry verification sampling. The use of nBPW is intended to minimize false-negative results in the recovery of pathogenic bacteria.

Purpose:  Ecolab has historically utilized a broad spectrum neutralizing Dey/Engley (DE) broth in validation studies. This study was conducted to compare D/E broth to nBPW in neutralizing sanitizer carryover.

Methods:  The study evaluated acidified sodium chlorite (ASC) and peroxyacetic acid (PAA) neutralization using D/E and nBPW for whole chicken carcass rinses. PAA and ASC were diluted with the rinsates at 1, 13, and 30 ml representing the zero-, one-, and five-min drip time equivalent volumes, respectively. The solutions were spiked with a 10⁵ CFU/ml mixture of five nalidixic acid-resistant Salmonella enterica serovars, and incubated at 4^ᵒC for 24 h before enumeration analysis using brilliant green sulfa agar supplemented with 100 ppm nalidixic acid. All experiments were performed in triplicates.

Results:  Salmonella recovery was observed in all samples. PAA performance was similar across the sample types. At zero-min drip time equivalent, the recovery of Salmonella from ASC carry-over samples was slightly reduced in nPBW compared to D/E (4.8 log/ml and 5.5 log/ml, respectively), suggesting that antimicrobial activity of ASC may not be completely inhibited by nBPW, and thus can potentially contribute to the false-negative results in the recovery of Salmonella during sampling, especially at inadequate drip times.

Significance:  These findings show the equivalency or potential advantage of D/E over nBPW. This data highlights the importance of performing neutralization verification in poultry validation studies.