Co-infection of Salmonella with a Salmonella “probiotic” strain that is neither virulent nor capable of consuming F-Asn (a SPI1 SPI2 fraR-BDAE ansB mutant) led to a dramatic 10,000-fold reduction in CFU and a 1000-fold reduction in lipocalin-2, a proxy marker of inflammation. This evidence concerns the gene SPI1 and coinfection.