Fig 1.
Decreased growth of S. aureus CBS2016-05 and PS/BAC/317/16/W during PC storage in comparison to trypticase soy broth (TSB).
Time-course growth curves of CBS2016-05 and PS/BAC/317/16/W in (A) TSB and (B) PCs. The samples were inoculated in three independent replicates with an initial concentration of ~4E+06 CFU/mL. The curves were generated using log10 CFU/ml values calculated at 0, 24, 48, 72, 96 and 144 hr.
Fig 2.
The PC environment induces expression of key virulence and immune evasion gene pathways in CBS2016-05.
PCA plots (PCs vs TSB) of S. aureus (A) CBS2016-05 and (B) PS/BA/317/16/W strains showing the overall structure of the transcriptomic data. (C) Volcano plot illustrating differentially expressed genes (DEGs) (log fold-change ≥ 2 or ≤ -2, p<0.05) by S. aureus CBS2016-05 in PCs versus TSB. (D) Volcano plot illustrating differentially expressed genes (DEGs) (log fold-change ≥ 2 or ≤ -2, p<0.05) by S. aureus PS/BA/317/16/W in PCs versus TSB. Scattered blue and red dots represent down-regulated and up-regulated DEGs, respectively, with significant differences indicated by -log(10) p-value < 0.05.
Table 1.
List of selected highly differentially expressed genes from S. aureus CBS2016-05 and PS/BAC/317/16/W spiked-PCs vs spiked-TSB.
Fig 3.
RT-qPCR showing differentially expressed genes in PCs versus trypticase soy broth (TSB).
RT-qPCR of eleven randomly selected transcripts with differential gene expression (DGE) in S. aureus CBS2016-05 and PS/BAC/317/16/W strains in PCs versus TSB. The bars indicate the relative fold change in mRNA expression. The gyrase gyrA gene was employed as a normalization control.
Fig 4.
S. aureus growth in PCs induces platelet activation and apoptosis.
PC units were spiked with S. aureus CBS2016-05 and incubated under standard PC condition and analyzed at 0, 24 and 144 hr. Non-spiked PC units were used as a baseline. (A) Representative FACS plots showing modulation in different markers used for assessment of platelet activation and functionality. (B) FACS analysis of platelets revealed significant decrease in expression of GPIIb (CD41, integrin αIIb), GPIbα (CD42b), whereas P-selectin CD62P) and phosphatidylserine (annexin V) showed significantly increased expression in spiked vs non-spiked platelets in a cell density dependent manner. Spiked PCs also showed significant decrease in MitoTrack Red FM and Calcein AM positive platelets. Asterisks indicate statistical significance (* P<0.05, ** P<0.01, *** P<0.001, n = 3).