Evaluation of FISH for Blood Cultures under Diagnostic Real-Life Conditions.

Background: The study assessed a spectrum of previously published in-house fluorescence in-situ hybridization (FISH) probes in a combined approach regarding their diagnostic performance with incubated blood culture materials.

Methods: Within a two-year interval, positive blood culture materials were assessed with Gram and FISH staining. Previously described and new FISH probes were combined to panels for Gram-positive cocci in grape-like clusters and in chains, as well as for Gram-negative rod-shaped bacteria. Covered pathogens comprised spp., such as spp., spp., including , and spp., like , and , such as and spp., , and spp.

Results: A total of 955 blood culture materials were assessed with FISH. In 21 (2.2%) instances, FISH reaction led to non-interpretable results. With few exemptions, the tested FISH probes showed acceptable test characteristics even in the routine setting, with a sensitivity ranging from 28.6% spp.) to 100% (6 probes) and a specificity of >95% in all instances.

Conclusion: If sophisticated rapid diagnostic methods like mass spectrometry from blood culture materials are not available, FISH provides an option for rapid differentiation for laboratories in resource-limited settings.