Purpose: The objective of this study was to elucidate the invasion mechanism of S. aureus into Caco-2 cell.
Methods: Five S. aureus strains (S. aureus KACC11596, S. aureus KACC10768, S. aureus KACC10778, S. aureus KACC13236 and S. aureus NCCP10862) were examined for Caco-2 cell invasion, and one strain, which invaded Caco-2 cell, was selected. The strain was then analyzed with iTRAQ (isobaric tags for relative and absolute quantification) to identify proteins related to Caco-2 cell invasion. The genes, which express the indentified proteins, were searched, and a mutant strain was prepared by knocking out genes using pIMAY and E. coli DC10B strain. Eventually, invasion efficiency was compared between the wild type and the mutant type of S. aureus.
Results: Invasion efficiency of five strains were compared, and S. aureus KACC10768 had significantly higher (P < 0.05) invasion efficiency than other strains. The result of iTRAQ analysis showed that pyruvate formate lyase (Pfl) was upregulated in S. aureus KACC10768 compared to other strains. This result suggested that Pfl was the most frequent protein related to the invasion of S. aureus KACC10768. Thus, pflB gene of S. aureus was mutated, and S. aureus KACC10768 ΔpflB mutant had decreased Caco-2 cell invasion efficiency by 35% compared to the wild type.
Significance: This result indicates that S. aureus having high expression of pflB gene may cause foodborne illness by infection.