Peroxyacetic acid treatment significantly reduced Campylobacter jejuni culturability but not viability on chicken breasts

Campylobacter is the leading bacterial cause of foodborne illness in the United States with chicken as the primary source of infections. It can enter a viable but nonculturable (VBNC) state under stress, where cells remain intact (i.e., viable) but cannot grow in conventional culture media (i.e., nonculturable). We evaluated the antimicrobial and VBNC-inducing activity of peroxyacetic acid (PAA), a poultry processing antimicrobial that causes oxidative and acid stress. We inoculated Campylobacter onto chicken breasts and treated them with 500 ppm PAA for 10 s via spray or immersion, and quantified culturable cells via direct plating and viable cells via viability Quantitative Polymerase Chain Reaction (qPCR). Immediately after treatment, immersion insignificantly reduced the viable Campylobacter population by 0.3 ± 0.2 log₁₀ (p = 0.99) but significantly reduced the culturable population by 0.8 ± 0.1 log₁₀ (p < 0.001), while spray insignificantly reduced the viable population by 0.2 ± 0.2 log₁₀ (p = 1.00) and the culturable population 0.5 ± 0.1 log₁₀ (p = 0.11). This suggests that PAA treatment induced a small subpopulation of 0.6 ± 0.2 log₁₀ CFU/mL (immersion) and 0.3 ± 0.2 log₁₀ CFU/mL (spray) into a VBNC state. PAA did not have a significant additional antimicrobial effect after post-treatment sample storage at 4 °C for up to 24 h. However, environmental stressors significantly reduced the population of viable Campylobacter. Overall, the culture-based plating method overestimated the antimicrobial effect of PAA by up to 1.0 ± 0.3 log₁₀ due to VBNC. These findings highlight that combining culture-based and molecular methods in challenge studies can provide more accurate data on Campylobacter die-off.