Gene-expression profiling of gram-positive and gram-negative sepsis in critically ill patients.

Objective: It is unclear whether the host response of gram-positive sepsis differs from gram-negative sepsis at a transcriptome level. Using microarray technology, we compared the gene-expression profiles of gram-positive sepsis and gram-negative sepsis in critically ill patients.

Design: A prospective cross-sectional study.

Setting: A 20-bed general intensive care unit of a tertiary referral hospital.

Patients: Seventy-two patients admitted to the intensive care unit.

Interventions: Intravenous blood was collected for leukocyte separation and RNA extraction. Microarray experiments were then performed examining the expression level of 18,664 genes in each sample.

Measurements And Main Results: There was no difference in the expression profile between gram-positive and gram-negative sepsis. The finding remained unchanged even when genes with lower expression level were included or after statistical stringency was lowered. There were, however, 94 genes differentially expressed between sepsis and control patients. These genes included those involved in immune regulation, inflammation, and mitochondrial function. Hierarchical cluster analysis confirmed that the difference in gene expression profile existed between sepsis and control patients but not between gram-positive and gram-negative patients.

Conclusions: Gram-positive sepsis and gram-negative sepsis share a common host response at a transcriptome level. These findings support the hypothesis that the septic response is nonspecific and is designed to provide a more general response that can be elicited by a wide range of different microorganisms.