Preparation and biodistribution of [131I]linezolid in animal model infection and inflammation

Current Status of SPECT Radiopharmaceuticals for Specific Bacteria Imaging

Imaging infection still represents a challenge for researchers. Despite nuclear medicine (NM) offers valuable tools able to discriminate between infections and inflammation, there is an unmet clinical need to develop new strategies able to specifically target the causative pathogen, to select the best antimicrobial treatment for each patient and to accurately assess therapeutic efficacy. These aspects are commonly addressed by microbiology or histology but the diagnosis often relies on invasive procedures that are prone to contamination or sample bias and do not reflect the spatial heterogeneity of the infective process. Therefore, in the era of personalized medicine and treatment, a lot of efforts are in play to improve a personalized diagnosis. Molecular imaging is an ideal candidate for this purpose and, indeed, research is going fast to this direction aiming to find more selective and proper antimicrobial treatments and to overcome broad-spectrum antibiotic use, which still represents the major cause of bacterial drug-resistance. Several approaches for specifically image bacteria have been proposed and provided encouraging perspectives in preclinical studies. Nevertheless, the majority of these promising approaches are still confined in "bench stages" and crucial issues still need to be addressed before their translation in clinical practice. This review will focus on radiolabeled antibiotics for SPECT imaging of bacteria, their mechanisms of action, their potentiality and limitations for "bed-side" applications.

Evaluation of 99mTechnetium-Vancomycin Imaging Potential in Experimental Rat Model for the Diagnosis of Infective Endocarditis

BACKGROUND

Infective endocarditis (IE) is an infection of the heart's endocardial surface. In recent years, nuclear imaging methods have gained importance in the diagnosis of IE. The present study aims to investigate the imaging potential of ^99mTc-labeled vancomycin (^99mTc-Vancomycin) as a new agent that would enable the diagnosis of IE in its early stages when it is difficult to diagnose or has small vegetation in the experimental rat model.

METHODS

^99mTc-Vancomycin scintigraphy was evaluated for its accumulation in IE with Staphylococcus aureus performed in an experimental rat model. Serial planar scintigraphic and biodistribution analysis of infected vegetations are compared to rats with sterile vegetations. The heart was identified as an infected organ, the liver was identified as a non-infected organ and the heart/liver uptake ratio (T / NT ratio) was compared between infective endocarditis and sterile endocarditis groups.

RESULTS

Planar scintigrams (in vivo measurements) showed more uptake in the heart of rats in the infective endocarditis group compared to the uptake in the heart of rats in the sterile endocarditis group, but this difference was not statistically significant (p>0.05). From the ex vivo measurements, the ^99mTc-Vancomycin heart uptake increased significantly (p = 0.016), liver uptake was significantly decreased (p = 0.045) and the T/NT ratio was significantly higher (p = 0.014) in the infective endocarditis group compared to the sterile endocarditis group.

CONCLUSION

In this experimental study, ^99mTc-Vancomycin scintigraphy ensured the detection of ex vivo infected tissue in a rat model of IE. In addition, the absence of significant ^99mTc-Vancomycin uptake in the sterile endocarditis group indicates that this agent targeted the infected tissue instead of the sterile inflammatory tissue. Finally, this agent should also be evaluated with animal- specific imaging devices.

Synthesis, Radiolabeling, and Bioevaluation of Bis(Trifluoromethanesulfonyl) Imide

Imidazolium salts have antitumor potential and toxicological effects on various microorganisms. The authors' aim is to synthesize a new imidazolium salt and to assess its pharmacokinetic and antitumor potentials by in vitro and in vivo studies. In this study, bis(trifluoromethanesulfonyl) imide (ITFSI) was synthesized and labeled with (131)I using the iodogen method. The efficiency of radiolabeling was determined with high yield (95.5% ± 3.7%). Pharmacokinetic properties of the compound were investigated in albino Wistar rats using radiolabeled compound. The radiolabeled compound ((131)I-ITFSI) has been stable during a period of 3 hours in human serum. The uptake of (131)I-ITFSI reached maximum in the spleen, liver, and blood at 60 minutes, large intestine and heart at 30 minutes, and ovary at 120 minutes. It is observed that intracellular uptake of the radiolabeled compound is higher in the CaCo-2 (colon adenocarcinoma tumor) cell line than HEK-293 (human epithelial kidney) cell line. In further study, antitumor potential of ITFSI on a colon adenocarcinoma tumor-bearing animal model may be investigated.