INNOVATIVE STRATEGIES FOR THE CONTROL OF CAMPYLOBACTER JEJUNI IN AGRI-FOODS

Abstract

The aims of this thesis project are to study the interactions between antimicrobials, identify the adaptive molecular mechanism of synergistic antimicrobial combinations, and develop an innovative antimicrobial packaging to control Campylobacter jejuni in raw chicken meat. We identified additive and synergistic combinations consisting of cinnamon oil, encapsulated curcumin, and/or zinc oxide nanoparticles (ZnO NPs) using an innovative mathematical model to avoid some over- or under-estimation of synergism determined by the conventional methods. The whole transcriptome sequence analysis (RNA-Seq) of single and combined treatments showed that each single antimicrobial played a different role in synergism, while combined treatments altered unique gene expressions that were not affected by any single treatment. Many of these genes are involved in signaling and chemotaxis, amino acid synthesis, protein translation, and/or bacterial cell wall synthesis. Unlike dual antimicrobial treatments, all single treatments resulted in under-expression of a major facilitator superfamily encoding gene involved in developing antimicrobial resistance. ZnO NPs alone altered the greatest number of genes and functions in C. jejuni compared to any other single, dual or triple antimicrobial treatments. We included ZnO NPs into packaging material for the control of Campylobacter in raw chicken meat. Functionalized pad was placed underneath chicken meat to investigate the antimicrobial effect against C. jejuni. Immobilized ZnO NPs reduced C. jejuni from ~log 4 CFU/chicken sample to undetectable level during storage at 4°C. We validated no nanoparticle migration onto the chicken meat after treatment with immobilized ZnO NPs in the functionalized pad. Analysis by inductively coupled plasma-optical emission spectroscopy showed that Zn level increased from 0.02 to 0.17 mg/cm2 in the treated chicken meat. Inactivation of C. jejuni was associated with the increase of lactic acid produced by Lactobacillus in chicken meat in a pH dependent manner.