Abstract
The diffusion of antibiotics in endocarditis vegetation bacterial masses has not been described, although it may influence the efficacy of antibiotic therapy in endocarditis. The objective of this work was to assess the diffusion of ofloxacin in experimental endocarditis vegetation bacterial masses using synchrotron-radiation UV fluorescence microspectroscopy. Streptococcal endocarditis was induced in 5 rabbits. Three animals received an unique IV injection of 150 mg/kg ofloxacin, and 2 control rabbits were left untreated. Two fluorescence microscopes were coupled to a synchrotron beam for excitation at 275 nm. A spectral microscope collected fluorescence spectra between 285 and 550 nm. A second, full field microscope was used with bandpass filters at 510–560 nm. Spectra of ofloxacin-treated vegetations presented higher fluorescence between 390 and 540 nm than control. Full field imaging showed that ofloxacin increased fluorescence between 510 and 560 nm. Ofloxacin diffused into vegetation bacterial masses, although it accumulated in their immediate neighborhood. Fluorescence images additionally suggested an ofloxacin concentration gradient between the vegetation peripheral and central areas. In conclusion, ofloxacin diffuses into vegetation bacterial masses, but it accumulates in their immediate neighborhood. Synchrotron radiation UV fluorescence microscopy is a new tool for assessment of antibiotic diffusion in the endocarditis vegetation bacterial masses.
Highlights
Bacterial endocarditis is a severe infection developing at the surface of the cardiac valvular apparatus
Comparison of control and ofloxacin vegetation spectra Spectra extracted from vegetation maps of 3 ofloxacin-treated animals and 2 control rabbits were stratified on the 339 nm peak intensity by treatment status, and by tissue class
This study demonstrates that synchrotron-radiation UV fluorescence microspectroscopy detects ofloxacin in the endocarditis vegetation despite the autofluorescence of vegetation itself
Summary
Bacterial endocarditis is a severe infection developing at the surface of the cardiac valvular apparatus. The diffusion of antibiotics in the endocarditis vegetation is a key determinant for their activity in this difficult-to-treat infection [2]. As the endocarditis vegetation is an avascular lesion, antibiotics diffuse into it from its periphery to its centre [3]. The diffusion of antibiotics in the experimental endocarditis vegetation has been assessed by autoradiography for various antibiotics [3,4,5,6]. Due to autoradiography poor spatial resolution, the diffusion of antibiotics within the vegetation bacterial masses has not been studied. This is a matter of concern, because poor antibiotic diffusion in vegetation bacterial masses may be a risk factor for treatment failure
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