Quantitative rt-PCR holds promise as a screening tool for patients with severe sepsis

The aim of the present study was to determine if the quantification of bacterial 16S rDNA could be clinically useful in predicting patients at increased risk of developing septic shock.

A retrospective study of patients with positive blood cultures taken on arrival to the ED. An EDTA sample was collected simultaneously with blood cultures and assayed by polymerase chain reaction to quantitate the bacterial 16S rDNA load. Descriptive and clinical data were collected from the medical record and this was blinded to the 16S rDNA result. Subsequently, the 16S rDNA result was compared with illness severity markers including septic shock and death to determine the relationship between the 16S rDNA load and illness severity.

98 patients (mean age 61 ± 20 years, range 18-92) with positive blood cultures were studied, most commonly growing Escherichia coli (n= 25) and Staphylococcus aureus (n= 23). 16 (16%) died. There were 42 (43%) 16S rDNA positive patients. A high 16S rDNA load was associated with an increased risk of developing delayed septic shock (OR 21.9, 95% CI 2.5-192.6) in comparison with either a low or negative 16S rDNA load; with a mortality OR 4.6 (95% CI 0.9-23.5).

The quantitative assay for 16S rDNA might be a useful screening tool to detect severe sepsis in those whom it might not be clinically suspected. However, prospective studies are required to further assess the clinical usefulness of this assay.