Probiotic application reduces Salmonella Enteritidis contamination in layer hatching eggs and embryos

Poultry meat and eggs are major sources of foodborne salmonellosis in the United States, with contaminated hatching eggs acting as a key transmission route for Salmonella Enteritidis (SE) from hatchery to farm. Although chemical disinfectants are used to sanitize hatching eggs, they often fail to eliminate internalized pathogens, increasing the risk of embryo contamination and subsequent transmission to hatchlings. This study explores probiotics as a natural, organic-friendly alternative for sanitizing hatching eggs to reduce SE contamination. A total of 560 Lohman Lite hatching eggs, inoculated with a five-isolate mix of SE were sprayed with: Control (phosphate buffered saline), Lactobacillus rhamnosus NRRL-B-442 (LR; ∼8 log CFU/egg), Lactobacillus paracasei DUP 13076 (LP; ∼8 log CFU/egg), or peracetic acid (PAA; 0.4 %) and incubated for 18 days. SE and probiotic populations on the egg surface, inner shell membrane, and internal contents were enumerated at regular intervals. LR, LP and PAA treatments significantly reduced SE populations on the egg surface compared to the control (p < 0.05). By day 18, treated samples were negative for SE by enrichment, while ∼2.5 log CFU/egg of SE was recovered from control eggs. Although PAA effectively reduced surface contamination, trans-shell migration of SE was significantly higher in this group compared to LR and LP. On day 18, SE counts on the inner shell membrane were ∼4 and 3 log CFU/egg in control and PAA groups, respectively, but below detection limits in LR and LP. Internal content sampling, including embryos, revealed <20 % SE positivity in probiotic-treated eggs compared to 60-70 % in PAA and control groups. These findings demonstrate that probiotic application not only reduces surface contamination but also minimizes trans-shell SE migration and potential contamination in the developing embryos. Overall, early probiotic application may serve as an effective, natural intervention to reduce Salmonella Enteritidis (SE) contamination in hatching eggs and developing embryos. In turn, this could lower SE prevalence in hatchlings and limit its spread to grow-out farms.