Salmonella infantis, a serovar of Salmonella enterica, is an emerging pathogen that’s closely related to S. typhi, which causes typhoid fever. It has long been hypothesized that S. typhi does this through the action of its ADP ribosylating toxin (ADPRT), a type of toxin also found in Vibrio cholerae and Bordetella pertussis. As a bacteria which has recently been increasing in virulence and prevalence, it stands to reason that S. infantis may also possess such a toxin. Identification of a novel S. infantis toxin would lend insight into the mechanism of disease from S. infantis, as well as providing a target for vaccination and other treatment. Recent advances in analytical software and increases in the breadth and depth of online databases enable toxin identification to occur almost completely in silico; use of methods like DELTA-BLAST and Clustal Omega yielded forty-seven potential toxins from S. infantis, all labeled “pertussis toxin”. Further organization of these toxins into nine groups and careful alignment with known ADPRTs revealed that first, there was a high degree of variability among these toxins, and second, that several have 50% or less similarity to known ADPRTs like ArtA, which seems to be the most similar known toxin. Further analysis and stringent elimination of more similar groups leaves a single group with 30% similarity to ArtA as a probable example of a novel S. infantis toxin. Analysis of S. infantis genomes reveals that the toxins are almost certainly carried in prophage regions, but the original phage cannot definitively be identified. Further cloning and isolation will reveal whether this group is representative of an active toxin with APDRT capabilities, but certain structural characteristics seem to indicate that it is
