New Microbiological Techniques in the Diagnosis of Bloodstream Infections.

BACKGROUND: When a bloodstream infection is suspected, the preliminary and definitive results of culture-based microbiological testing arrive too late to have any influence on the initial choice of empirical antibiotic treatment.

METHODS: This review is based on pertinent publications retrieved by a selective search of the literature and on the authors' clinical and scientific experience.

RESULTS: A number of technical advances now enable more rapid microbiological diagnosis of bloodstream infections. DNA- based techniques for the direct detection of pathogenic organisms in whole blood have not yet become established in routine use because of various limitations. On the other hand, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has become available for routine use in clinical laboratories and has markedly shortened the time to diagnosis after blood samples that have been cultured in automated blood-culture systems turn positive. Further developments of this technique now enable it to be used directly for blood cultures that have been flagged positive, as well as for subcultures that have been incubated for only a short time on a solid nutrient medium. The microbial biomass of the subculture can also be used in parallel for more rapid susceptibility testing with conventional methods, or, in future, with MALDI-TOF MS.

CONCLUSION: The potential of all of these new techniques will only be realizable in practice if they are optimally embedded in the diagnostic process and if sufficient attention is paid to pre-analytical issues, particularly storage and transport times.