Exploring differentially expressed genes of Staphylococcus aureus exposed to human tonsillar cells using RNA sequencing

The nose and the throat are the most predominant colonizing sites of Staphylococcus aureus, and colonization is a risk factor for infection. Nasal colonization is well described; however, we have limited knowledge about S. aureus throat colonization. The main objective of this study was to explore differentially expressed genes (DEGs) in S. aureus throat isolate TR145 exposed to human tonsil epithelial cells (HTEpiC) by using RNA sequencing (RNA-seq) and pathway analysis. DEGs in S. aureus at 1 or 3 hours (h) interaction with its host were explored. S. aureus was co-cultured in absence and presence of tonsillar cells at 1 or 3 h. Over the 3 h time frame, the bacteria multiplied, but still caused only minor cytotoxicity. Upon exposure to tonsillar cell line, S. aureus changed its transcriptomic profile. A total of 508 DEGs were identified including unique (1 h, 160 DEGs and 3 h, 78 DEGs) and commonly shared genes (1 and 3 h, 270 DEGs). Among the DEGs, were genes encoding proteins involved in adhesion and immune evasion, as well as iron acquisition and transport. Reverse transcription qPCR was done on selected genes, and the results correlated with the RNA-seq data. We have shown the suitability of using HTEpiC as an in vitro model for investigating key determinants in S. aureus during co-incubation with host cells. Several DEGs were unique after 1 or 3 h exposure to host cells, while others were commonly expressed at both time points. As their expression is induced upon meeting with the host, they might be explored further for future targets for intervention to prevent either colonization or infection in the throat.