The antibiotics resistance mechanism and pathogenicity of cold stressed Staphylococcus aureus

Staphylococcus aureus was one of the most common foodborne pathogens around the world. S. aureus displayed strong tolerance to low temperature (4 degrees C and - 20 degrees C) at which the foods are usually stocked. Here, the antibiotic resistance, biofilm-formation and virulence of S. aureus under cold stress were investigated. The results demonstrated that the MIC of S. aureus CICC10201 against quinolones and aminoglycosides enhanced 4-fold after being stressed at 4 degrees C and - 20 degrees C for 4 weeks. After cold stressed for 4 weeks, the efflux pump gene norA of S. aureus CICC10201 was over-expressed > 50-fold. The mutation of the target-site at position 410 of subunitGrIA, in which the tyrosine residue mutated into phenylalanine, reduced the binding efficiency of quinolones to S. aureus CICC10201. Meanwhile, biofilm-forming ability of S. aureus W-3 cells were enhanced with post-cold stress because of up-regulation of icaA and icaD gene, and the down-regulation of the icaR gene. Moreover, the mRNA expression of some virulence factors in S. aureus CICC10201 or W-3 were increased significantly. It reminded that thoroughly sterilizing the foods which were stored in the refrigerator for a long time are critical to reduce food contamination caused by S. aureus infection.