Influence of Live Attenuated Salmonella Vaccines on Cecal Microbiome Composition and Microbiota Abundances in Young Broiler Chickens

The study aimed to investigate the effect of live attenuated Salmonella vaccines on commensal gut bacteria in young broiler chickens. For this purpose, three different commercial live attenuated Salmonella vaccines, namely; AviPro Salmonella Vac T (S. Typhimurium vaccine), AviPro Salmonella Vac E (S. Enteritidis vaccine) and AviPro Salmonella DUO (combined vaccine) were used. Two-days old broiler chicks were orally vaccinated and sampled on day 16 post hatch (14 days post vaccination). Total genomic DNA was extracted from cecal contents, 16S rRNA V4 region amplified by PCR, followed by Next generation sequencing. The sequencing was performed at Gene Tech Lab (KU Leuven, Belgium), using the Illumina MiniSeq platform and paired-end reads (2x150 bp) were generated. Vaccination is currently considered the most effective prophylactic approach to Salmonella control in poultry farms. Vaccines have thus become one of the non-antibiotic alternatives to Salmonella, following the ban on antibiotics use in farm animals due to resistance. Although both inactivated and live attenuated Salmonella vaccines are commercially available, live attenuated vaccines are mostly preferred. This is because they can elicit both cellular and humoral response, with the former being most relevant for the clearance of intracellular pathogens like Salmonella. Being live bacteria, the attenuated Salmonella vaccines which are mostly orally administered, need to colonize the gut for it to efficiently function. The effect this will have to the commensal gut bacteria is not clearly known. It is, however, well established that commensal gut bacteria apart from their nutritional function, play an important role in development, training, functioning and immunomodulation of the host immunity. Thus, understanding the influence of live attenuated vaccines on gut microbiota, would help to design more improved Salmonella control strategies against this zoonotic pathogen.