Seeing is believing: Can biofilm diagnostics guide individualized therapy in endocarditis?

Introduction

In Infective Endocarditis (IE), early diagnosis of the causative microorganism is crucial for correct antibiotic therapy, which improves the patients’ outcome.

Objectives

We studies the impact of biofilm formation in IE samples.

Materials & methods

We used Fluorescence in situ Hybridization (FISH) combined with 16S rRNA-gene PCR and sequencing to visualize and identify the infectious agents in native as well as prosthetic valves and to study any biofilm formation. The signal intensity of the fluorescence-labelled FISH probes correlates to a high ribosome content of the bacteria indicating metabolic activity at the time point of surgery. We developed a spacer FISH assay for the detection of the 16S-23S intergenic spacer region that is only present in actively transcribing cells to detect the activity of bacterial cells more precisely on a single cell level.

Results

FISH visualized bacteria in the heart valves ranging from single cells to highly organized biofilms. Interestingly, we found FISH positive bacteria in culture negative samples and samples from patients under antibiotic therapy. Using the spacer FISH, we visualized positive microbial cells in heart valves of patients under adequate therapy. Preliminary data point to a correlation between the biofilm state and treatment inefficiency.

Conclusion

FISH/PCR not only allows timely identification of the pathogens in IE, but also biofilm-staging and visualization of the effect of antimicrobial therapy at time of surgery. The technique provides crucial information for successful targeted antibiotic therapy, and it might guide therapeutical decisions in relation to biofilm state in the future.