Invasion of Intestinal Cells by Staphylococcus aureus is Mediated by Pyruvate Formate Lyase (Pfl) Protein

Abstract

Staphylococcus aureus is a known enterotoxin-producing foodborne pathogen; however, the invasion mechanism of the bacterium into intestinal cells remains unclear. The aim of this study was to determine whether S. aureus can invade Caco-2 cells, and to elucidate the gene responsible for this invasion. Caco-2 cells were infected with S. aureus strains NCCP10862, KACC13236, KACC10768 and KACC11596, and their invasion efficiencies were evaluated. Proteins found in the invasive and noninvasive S. aureus strains were labelled with isobaric tags for relative and absolute quantification (iTRAQ), and the gene encoding the protein responsible for S. aureus invasion was deleted using a temperature-sensitive plasmid, pIMAY. The Caco-2 cell invasion efficiencies of the wild type and mutant S. aureus were then compared. Among the S. aureus strains, only NCCP10862 and KACC10768 were able to invade Caco-2 cells, and these strains had a higher level of pyruvate formate lyase (Pfl) protein expression than that of the noninvasive strains. Therefore, a pflB-deletion mutant of KACC10768 was prepared, which revealed a 60% decrease in invasion efficiency when compared to the wild type. These results indicate that certain S. aureus strains can invade intestinal cells, and the protein encoded by the pfl gene is involved in this invasion.