AUTHOR=Chen Sujuan , Feng Zheng , Sun Hualu , Zhang Ruonan , Qin Tao , Peng Daxin 

TITLE=Biofilm-Formation-Related Genes csgD and bcsA Promote the Vertical Transmission of Salmonella Enteritidis in Chicken

JOURNAL=Frontiers in Veterinary Science

VOLUME=7

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.625049

DOI=10.3389/fvets.2020.625049

ISSN=2297-1769

ABSTRACT=<p>The contamination of <italic>Salmonella</italic> Enteritidis in eggs and chicken meat via vertical transmission has become a worldwide public health concern. Biofilm formation by <italic>S</italic>. Enteritidis further enhances its antibacterial resistance. However, whether genes related to biofilm formation affect the level of vertical transmission is still unclear. Here, <italic>S</italic>. Enteritidis mutants Δ<italic>csgD</italic>, Δ<italic>csgA</italic>, Δ<italic>bcsA</italic>, and Δ<italic>adrA</italic> were constructed from wild type strain C50041 (WT), and their biofilm-forming ability was determined by Crystal violet staining assay. Then the median lethal dose (LD<sub>50</sub>) assay was performed to determine the effects of the selected genes on virulence. The bacterial load in eggs produced by infected laying hens via the intraperitoneal pathway or crop gavage was determined for evaluation of the vertical transmission. Crystal violet staining assay revealed that <italic>S</italic>. Enteritidis mutants Δ<italic>csgD</italic>, Δ<italic>csgA</italic>, and Δ<italic>bcsA</italic>, but not Δ<italic>adrA</italic>, impaired biofilm formation compared with WT strain. Furthermore, the LD<sub>50</sub> in SPF chickens showed that both the Δ<italic>csgD</italic> and Δ<italic>bcsA</italic> mutants were less virulent compared with WT strain. Among the intraperitoneally infected laying hens, the WT strain-infected group had the highest percentage of bacteria-positive eggs (24.7%), followed by the Δ<italic>adrA</italic> group (16%), Δ<italic>csgA</italic> group (9.9%), Δ<italic>bcsA</italic> group (4.5%), and Δ<italic>csgD</italic> group (2.1%). Similarly, among the crop gavage chickens, the WT strain group also had the highest infection percentage in eggs (10.4%), followed by the Δ<italic>csgA</italic> group (8.5%), Δ<italic>adrA</italic> group (7.5%), Δ<italic>bcsA</italic> group (1.9%), and Δ<italic>csgD</italic> group (1.0%). Our results indicate that the genes <italic>csgD</italic> and <italic>bcsA</italic> help vertical transmission of <italic>S</italic>. Enteritidis in chickens.</p>