Cytopathic effects observed upon expression of a repressed collagenase gene present in Salmonella and related pathogens: mimicry of a cytotoxin from multiple antibiotic-resistant Salmonella enterica serotype Typhimurium phagetype DT104

Recently, we reported that certain strains of Salmonella enterica serovar Typhimurium phagetype DT104 (DT104) secrete a putative cytotoxin. While searching for the gene that encodes this toxin, we noted a previously reported but uncharacterized DNA fragment (clg) in Salmonella that could be potentially relevant to cytotoxin-like activity. Therefore, we cloned and expressed clg in cytotoxin-negative Escherichia coli and Salmonella and subsequently assessed the bioactivity of Clg in vitro and in vivo. Lysates containing Clg from both expression hosts exerted cytopathic effects on murine enterocytes while semi-purified Clg was determined to be cytopathic to HEp-2 cells. Sequence and RT-PCR analyses of the clg gene indicated that a homologue of clg exists in different Gram-negative bacteria although the gene is not expressed in vitro. Although Clg-mediated lesions are similar to those mediated by the DT104 cytotoxin, further investigations are necessary to examine the relationship between these two proteins in DT104. Nonetheless, we report here a defined Salmonella protein that is capable of inflicting damage on tissue culture cells and murine enterocytes.