Role of fnr and narL genes in the survival of Salmonella Typhimurium in chicken macrophages

Pashupathi, M., Sahoo, P.R., Sreenilav, V., Mishra, R., Priyadarsini, S., Nikhil, K.C., Saxena, M. and Kumar, A. 2024. Role of fnr and narL genes in the survival of Salmonella Typhimurium in chicken macrophages. Indian Journal of Poultry Science, 59(1): 85–91.

Salmonella is a gram negative, facultative anaerobic rod shaped intracellular bacteria having zoonotic importance. Salmonellosis is one of the most common foodborne zoonosis in both developed and developing countries. It has been linked to foods such as raw meat, poultry, eggs, and dairy products. Poultry and poultry products are thought to account for half of the total route of Salmonella transmission. Eggs are the most commonly involved food commodity in Salmonella outbreaks followed by chicken meat. Salmonella has the ability to remain in an anaerobic environment required for pathogenesis and pathogenicity in hosts. A range of sensors and several global regulatory proteins like Fnr, ArcA/ArcB dual-complex (aerobic respiratory control) and NarX/NarL systems help the bacteria to survive in the intestine for successful infection. In this study, a double knock out mutant of fnr and narL was studied for its infection, survival, and metabolic modulation in the chicken macrophages. An increased expression of ATP citrate lyase and Acetyl co-A carboxylase reported in present study indicated the diversion of Tricarboxylic acid cycle to different pathways for avoiding more ATP production and causing induction of cytokines. The other defense activities such as antigen presentation (Major histocompatibility complex class-II), DUOX oxidase, and the cytokines IL-2 and IL-4 were found increased significantly as compare to wild type. Therefore, we are concluding that the deletion of fnr and narL genes made the Salmonella more susceptible to macrophage internal environment and hence easier and faster clearance.