Reactive oxygen species and reactive nitrogen species are double-edged swords in Salmonella infection.

Salmonella contains a group of serovars, which are more than just enteropathogenic bacteria but dangerous pathogens causing systemic infection of human, livestock, and poultry. As an innate immune response, inflammation induces reactive oxygen species (ROS) and reactive nitrogen species (RNS) production from host cells in response to Salmonella infection. Generally, ROS and RNS are regarded as bactericidal substances for their ability to oxidize and modify the bacterial biomolecules including proteins, DNA, RNA, lipids, etc. However, excessive ROS and RNS damage the functions of host cells through the destroy of host biomolecules. Salmonella inhibits ROS/RNS production, eliminates toxic ROS/RNS, and mends damaged DNA/proteins using specific enzymes or proteins to avoid the killing of ROS/RNS. In hypoxic intracellular environment or intestinal lumen, Salmonella exploits the chemical reaction products of ROS or RNS to promote its growth during infection. This review article provides deep insights for understanding the functions of ROS/RNS in Salmonella infection.