Multiplex real-time PCR and blood culture for identification of bloodstream pathogens in patients with suspected sepsis

Abstract

Severe sepsis is increasingly a cause of death. Rapid and correct initial antimicrobial treatment reduces mortality. The aetiological agent(s) cannot always be found in blood cultures (BCs). A novel multiplex PCR test (Septi Fast (alpha version)) that allows identification of 20 bacterial and fungal species directly from blood was used, comparatively with BC, in a multicentre trial of patients with suspected bacterial or fungal sepsis. Five hundred and fifty-eight paired samples from 359 patients were evaluated. The rate of positivity was 17% for BC and 26% for Septi Fast. Ninety-six microorganisms were isolated with BC, and 186 microorganisms were identified with Septi Fast; 231 microrganisms were found by combining the two tests. Of the 96 isolates identified with BC, 22 isolates were considered to be contaminants. Of the remaining 74 non-contaminant BC isolates available for comparison with Septi Fast, 50 were identified as a species identical to the species identified with Septi Fast in the paired sample. Of the remaining 24 BC isolates for which the species, identified in the BC, could not be detected in the paired Septi Fast sample, 18 BC isolates were identified as a species included in the Septi Fast master list, and six BC isolates were identified as a species not included in the Septi Fast master list. With Septi Fast, 186 microorganisms were identified, 12 of which were considered to be contaminants. Of the 174 clinically relevant microorganisms identified with Septi Fast, 50 (29%) were detected by BC. More than half of the remaining microorganisms identified with Septi Fast (but not isolated after BC) were also found in routine cultures of other relevant samples taken from the patients. Future clinical studies should assess whether the use of Septi Fast is of significant advantage in the detection of bloodstream pathogens. © 2009 The Authors Journal compilation © 2009 European Society of Clinical Microbiology and Infectious Diseases.