Biofilm Formation in Different Salmonella Serotypes Isolated from Poultry.

Little is known about Salmonella biofilm assembly, making the prevention of the disease a challenge in the poultry production chain. The objective of the present study was then to evaluate biofilm formation from different serotypes of Salmonella spp. in both polystyrene plates and eggshells. Salmonella Gallinarum and S. Minnesota were both classified as producers of biofilms of moderate intensity. Interestingly, S. Gallinarum produces biofilm even though being a serotype without flagellum and not having the lux gene in its genome, suggesting that there might be other important structures and genes associated with biofilm formation. Regarding Enteritidis, Typhimurium, Typhimurium variant, and Heidelberg serotypes, despite having high counts, BFI (Biofilm Formation Index) showed low biofilm production, probably due to the scarcity of extracellular matrix produced by such strains. A turkey eggshell model was then used for S. Enteritidis and S. Heidelberg biofilm formation. The results from the microbial count and scanning electron microscopy showed that Salmonella serotypes were also able to generate biofilm in eggshells, suggesting the presence of biofilms in poultry producing farms, a main concern for the poultry production industry.

Comparative genomics of a novel clade shed light on the evolution of the genus Erysipelothrix and characterise an emerging species.

Erysipelothrix sp. isolates obtained from a deadly outbreak in farmed turkeys were sequenced and compared to representatives of the genus. Phylogenetic trees-supported by digital DNA:DNA hybridization and Average Nucleotide Identity-revealed a novel monophyletic clade comprising isolates from pigs, turkeys, and fish, including isolates previously described as E. sp. Strain 2. Genes coding for the SpaC protein, typically found in E. sp. Strain 2, were detected in all isolates of the clade. Therefore, we confirm E. sp. Strain 2 represents a unique species that may be isolated from a broad host range, and the name "Erysipelothrix takahashiae" is suggested. Core genome analysis showed that the pathogenic species of this genus, E. rhusiopathiae and the clade E. sp. Strain 2, are enriched in core functionalities related to nutrient uptake and transport, but not necessarily homologous pathways. For instance, whereas the aerobic DctA transporter may uptake C4-dicarboxylates in both species, the anaerobic DcuC transporter is exclusive of the E. sp. Strain 2. Remarkably, the pan-genome analysis uncovered that genes related to transport and metabolism, recombination and repair, translation and transcription in the fish isolate, within the novel clade, have undergone a genomic reduction through pseudogenization. This reflects distinct selective pressures shaping the genome of species and strains within the genus Erysipelothrix while adapting to their respective niches.