Staphylococcus epidermidis biofilms transcriptome alterations upon incubation with whole human blood. Staphylococcus epidermidis

The ability of S. epidermidis to withstand the high bactericidal activity of the host’s blood is crucial for its systemic dissemination. Hence, in order to identify genes and pathways involved in the bacterium’s survival in human blood, we have characterized the transcriptome of S. epidermidis biofilms upon contact with human blood. Our results showed that genes whose transcription was increased in blood included those involved in biosynthesis and metabolism of amino acids, small molecules, carboxylic and organic acids, and cellular ketones. One of the striking changes, observed after 4 hours of exposure to human blood, was the increase in the expression of genes involved in iron utilization, suggesting iron acquisition is an important component of S. epidermidis survival in human blood. Overall design: Twenty-four hour S. epidermidis biofilms were incubated with either whole human blood or tryptic soy broth (TSB) during 2 or 4 hours at 37oC, 5% CO2 and slight agitation. RNA was then extracted and the transcriptomic libraries constructed. Differential gene expression calculations were performed using the transcriptome of biofilms at the start of the culture (T0h) as a control. This experiment was performed twice with blood collected from 6 healthy human donors under a protocol approved by the Partner’s Health Care System Institutional Review Board (Boston, MA, USA).