SlyA regulates the collagenase-mediated cytopathic phenotype in multiresistant Salmonella

Salmonella enterica serotype Typhimurium phagetype DT104 (DT104) is a foodborne pathogen with a multiresistant phenotype conferred by a genomic-based integron structure designated as SGI1. Recently, a novel cytopathic phenotype was ascribed to several isolates of DT104 recovered from veal calves. This phenotype is dependent upon clg, a gene encoding a collagenase in Salmonella. Using a novel transposon system and an RT-PCR assay for detection of clg expression, we identified SlyA as a regulator of the collagenase-mediated phenotype. The function of SlyA, in regards to clg expression, is to repress the synthesis of Clg. Derepression ensued in the absence of SlyA or in the presence of a truncated version of SlyA with the latter being relevant for maintenance of another virulence aspect mediated by SlyA, i.e. survival within macrophages. The SlyA-mediated effect on clg expression was restricted to DT104 and other Salmonella phagetypes and serotypes possessing SGI1 thus suggesting co-regulation by an SGI1-specific component.