Evaluation of 99mTc-UBI 29-41 scintigraphy for specific detection of experimental multidrug-resistant Staphylococcus aureus bacterial endocarditis.

AIM

The aim of this paper was to test the ability of technetium-99m labelled synthetic peptide UBI 29-41 scintigraphy (99mTc-UBI 29-41), composed of the antimicrobial peptide ubiquicidin, specifically targets microorganisms in to discriminate between infected and uninfected endocarditis using a rat model previously validated.

METHODS

99mTc-UBI 29-41 scintigraphy was evaluated for its accumulation in infective endocarditis (IE) with multidrug resistant Staphylococcus aureus (MRSA) performed in an experimental rat model, resembling early endocarditis in humans. Serial planar scintigraphic and biodistribution analysis of infected vegetations are compared to rats with sterile vegetations. Heart-to-lung uptake ratios (T/NT ratios) were calculated in both with in-vivo scintigraphy and in ex vivo tissue samples.

RESULTS

Bacterially infected vegetations were already observed at 15 min after injection of 99mTc-UBI 29-41 while no significant uptake was observed in sterile vegetations. Moreover, a good correlation (R2=0.819) was calculated between T/NT ratios of 99mTc-UBI 29-41 and the number of viable MRSA present in the infected vegetation. There was no correlation between the 99mTc-UBI 29-41 uptake and the weight of the vegetations in either case.

CONCLUSION

In this experimental study in rats, planar 99mTc-UBI 29-41 scintigraphy permitted early and specific detection of MRSA induced endocarditis. Furthermore, accumulation of the tracer depends on the number of viable MRSA and not on the weight of the vegetation. This proof of principle offers much promise that 99mTc-UBI 29-41 scintigraphy can be a dedicated non-invasive imaging tool for the early detection of infective endocarditis. Finally, this model has to be further evaluated with state-of-the art small imaging modalities.