Proof of principle: Quantification of viable Campylobacter in the context of excess dead Campylobacter in chicken rinses.

Using the method depicted in Fig. 3, we quantified log 2–3 viable C. jejuni in the context of log 2–2.5 excess of dead C. jejuni in two different chicken rinses (cRinse) with low (∼1.4 mg/ml of protein) and high concentrations of organic matter (∼7.8 mg/ml of protein). In italics, PMA was directly added to the samples and incubated for 15 min at 20°C; all other samples were centrifuged and resuspended in PBS prior to PMA staining for 15 min at 30°C. ΔCt of signal reduction from dead bacteria (SPC, Fig. 3, tubes 2 and 4) in the presence of 50–100 µM PMA was >10 for both matrices, whereas 20 µM PMA (without prior centrifugation before staining) resulted in ΔCt = 4.2 (cRinselow) and ΔCt = 2.1 (cRinsehigh). IPIU, intact and potentially infectious units.