Tabashsum, ZajebaCampylobacter is one of the prominent causative agents of acute gastroenteritis in the US and more than 70% of Campylobacter infections, known as Campylobacteriosis, are occurred through raw or undercooked poultry consumption or improper handling of contaminated poultry products. Moreover, reports show that the antibiotic resistance pattern of Campylobacter is persistent and in the absence of sub-therapeutic antibiotic growth promoter, colonization of this bacterial pathogen in poultry gut or on skin and the potential risk of cross-contamination of the finished poultry products are increasing, Therefore, both conventional and organic/pasture poultry farmers are searching for sustainable alternative to synthetic antibiotics which can reduce colonization and cross-contamination of poultry products with poultry-borne bacterial pathogens specifically Campylobacter. On the other hand, due to the consumers’ demand, majority poultry farmers are growing their chicks without sub-therapeutic growth promotor which leads to slow growth and higher mortality rates. Therefore, to make the poultry farming sustainable, farmers need alternative feed or water supplement which can promote poultry health and growth. Probiotics, prebiotics, or a combination of these two referred to as synbiotics, have emerged as a promising natural and alternative approach to sustainable animal farming. Probiotics and their metabolites such as conjugated linoleic acids (CLAs) play a crucial role in improving host health and act as antimicrobials against enteric pathogens. Our lab developed a genetically engineered probiotic, LC+mcra that can convert more CLA by over-expressing the mcra (myosin-cross-reactive-antigen) in Lactobacillus casei (LC). Further, prebiotic-like components such as bioactive phenolic extracts (BPEs) from berry pomace can stimulate the growth of beneficial microbes including LC, competitively inhibit growth of enteric bacterial pathogens, and promote the growth of chickens in a concentration-dependent manner when applied throughout the growth period. In our previous study, we observed that LC+mcra effectively eliminated Campylobacter jejuni (CJ) in co-culture condition as well as the cell free culture supernatants (CFCS) of LC+mcra was effective in growth reduction of CJ. LC+mcra and its CFCSs also reduced the adherence and invasion ability of CJ to both HD-11 and HeLa cells. Physicochemical properties and gene expressions related to CJ virulence were also altered by CFCSs treatments. These findings suggested, LC+mcra can be an alternative in controlling CJ growth along with other beneficial attributes of LC. Then, we aimed to enhance the efficiency of antimicrobial/beneficial activities of LC+mcra by combining BPEs. In mixed culture condition, LC+mcra in the presence of BPE reduced the growth of CJ more efficiently as well as the CFCS of LC+mcra in the presence of BPE. Interaction of CJ with cultured DF-1, HD-11, and HeLa were altered significantly. Further, combined treatments altered the physicochemical properties and expression of multiple virulence genes such as ciaB, cdtB, cadF, flaA, flaB of CJ. This finding indicates that BPE and LC+mcra in combination might be able to prevent colonization of CJ in poultry. So, in our present study at simulated gut conditions, we evaluated combined effect of LC+mcra and BPE in reducing growth of Campylobacter in cecum contents. Cecum contents were collected from chickens pre-inoculated with kanamycin resistant CJ (CJ-Km), incubated over 48h time period, while being supplemented with either BPE, CFCS from LC+mcra, or their combination. It was found that combined treatments were able to reduce both inoculated and naturally colonized Campylobacter more effectively. Microbiome analysis using 16S rRNA sequencing also revealed that combined treatments were capable of altering natural microflora positively within chicken cecum contents. Then, the effect of sustainable probiotics on CJ colonization and gut microbiome composition was evaluated using chicken as a model. A total of 120 chickens were used in duplicate trials to investigate the effectiveness of LC+mcra in decreasing CJ colonization by means of CJ-Km compared to the control group. We observed that LC+mcra could efficiently colonize various parts of the chicken gut and competitively reduce colonization of natural and challenged Campylobacter. Furthermore, 16S rRNA compositional analysis revealed lower abundance of Proteobacteria, higher abundance of Firmicutes, along with enriched bacterial genus diversity in gut of LC+mcra fed chicken. Outcomes of this study reveal high potential of LC+mcra as sustainable approach to decrease colonization of Campylobacter in poultry gut along with other beneficial attributes. So, we further evaluated the combined effect of LC+mcra and a low dose of BPE on Campylobacter colonization in chicken gut using a day-old chick model. Colonization of CJ-Km as well as the natural colonization of Campylobacter was reduced by the combined effect of LC+mcra and BPEs significantly at all time points. In the cecum contents of the LC+mcra and BPEs treatment group, there was notable change at phylum level microbiome compared to the control group. At genus level colonization of Lactobacillus was significantly higher (1.7 folds), Campylobacter colonization was reduced significantly (6.3 folds), and other microflora remained balanced due to the combined treatment of LC+mcra and BPEs. Therefore, LC+mcra with BPEs could be an alternative to improve the safety of poultry products and reduce campylobacteriosis in humans sustainably. The application period of this synbiotic compositions could be extended to improve the poultry growth rate as an additional benefit of the LC+mcra and BPEs.enDissertationBiologyAnimal sciencesCampylobacterMicrobiomePrebioticProbioticSynbiotic