AUTHOR=Thiam Mamadou , Wang Qiao , Barreto Sánchez Astrid Lissette , Zhang Jin , Ding Jiqiang , Wang Hailong , Zhang Qi , Zhang Na , Wang Jie , Li Qinghe , Wen Jie , Zhao Guiping 

TITLE=Heterophil/Lymphocyte Ratio Level Modulates Salmonella Resistance, Cecal Microbiota Composition and Functional Capacity in Infected Chicken

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.816689

DOI=10.3389/fimmu.2022.816689

ISSN=1664-3224

ABSTRACT=<p>The gastrointestinal microbiota plays a vital role in ensuring the maintenance of host health through interactions with the immune system. The Heterophil/Lymphocyte (H/L) ratio reflects poultry’s robustness and immune system status. Chickens with low H/L ratio are superior to the chickens with high H/L ratio in survival, immune response, and resistance to <italic>Salmonella</italic> infection, but the underlying mechanisms remain unclear. This study aimed to identify microorganisms associated with resistance to <italic>Salmonella</italic> Enteritidis infection in chickens based on the H/L ratio. The 16S rRNA and metagenomic analysis were conducted to examine microbiome and functional capacity between the 2 groups, and Short Chain Fatty Acids (SCFAs) and histopathology were conducted to explore the potential difference between susceptible and resistant groups at 7 and 21 days post-infection (dpi). The microbiome exploration revealed that low H/L ratio chickens, compared to high H/L ratio chickens, displayed a significantly higher abundance of <italic>Proteobacteria</italic> (<italic>Escherichia coli</italic>) and <italic>Bacteroidetes</italic> (<italic>Bacteroides plebeius</italic>) at 7 and 21 dpi, respectively. <italic>Anaerostipes</italic> (r = 0.63) and <italic>Lachnoclostridium</italic> (r = 0.63) were identified as bacterial genus significantly correlated with H/L (P &lt; 0.001). Interestingly, <italic>Bacteroides</italic> was significantly and positively correlated with bodyweight post-infection (r = 0.72), propionate (r = 0.78) and valerate (r = 0.82) contents, while <italic>Salmonella</italic> was significantly and negatively correlated with bodyweight post-infection (r = − 0.67), propionate (r = − 0.61) and valerate (r = − 0.65) contents (P &lt; 0.001). Furthermore, the comparative analysis of the functional capacity of cecal microbiota of the chickens with high and low H/L ratio revealed that the chickens with low H/L ratio possess more enriched immune pathways, lower antibiotic resistance genes and virulence factors compared to the chickens with high H/L ratio. These results suggest that the chickens with low H/L ratio are more resistant to <italic>Salmonella</italic> Enteritidis, and it is possible that the commensal <italic>Proteobacteria</italic> and <italic>Bacteroidetes</italic> are involved in this resistance against <italic>Salmonella</italic> infection. These findings provide valuable resources for selecting and breeding disease-resistant chickens.</p>