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Evaluation of a Novel Tc-99m Labelled Vitamin B12 Derivative for Targeting Escherichia coli and Staphylococcus aureus In Vitro and in an Experimental Foreign-Body Infection Model.

Baldoni D, Waibel R, Bläuenstein P, Galli F, Iodice V, Signore A, Schibli R, Trampuz A - Mol Imaging Biol (2015)

Bottom Line: The in vitro binding of [(99m)Tc]PAMA(4)-Cbl was 100-fold and 3-fold lower than the one of [(57)Co]Cbl for E. coli and S. aureus, respectively.Significantly higher retention occurred in cage fluids infected with S. aureus at 4 h and with E. coli at 8 h p.i. than in non-infected animals.Accumulation into infected cages was also higher than the one of [(99m)Tc]DTPA, which showed similar biodistribution in infected and sterile mice. [(57)Co]Cbl gradually accumulated in cages with peaks % ID between 3.58 and 4.83 % achieved from 24 to 48 h.

View Article: PubMed Central - PubMed

Affiliation: Infectious Diseases Research Laboratory, Department of Biomedicine, University Hospital, Basel, Switzerland.

ABSTRACT

Purpose: Vitamin B12 (cyanocobalamin, Cbl) is accumulated by rapidly replicating prokaryotic and eukaryotic cells. We investigated the potential of a Tc-99m labelled Cbl derivative ([(99m)Tc]PAMA(4)-Cbl) for targeting infections caused by Escherichia coli and Staphylococcus aureus. In vitro binding assays were followed by biodistribution studies in a mouse model of foreign body infection.

Procedures: E. coli (ATCC 25922) and S. aureus (ATCC 43335) were used as test strains. [(57)Co]Cbl, [(67)Ga]citrate and [(99m)Tc]DTPA served as reference compounds. The in vitro competitive binding of [(57)Co]Cbl or [(99m)Tc]PAMA(4)-Cbl, and unlabeled Cbl, to viable or killed bacteria, was evaluated at 37 and 4 °C. A cage mouse model of infection was used for biodistribution of intravenous [(57)Co]Cbl and [(99m)Tc]PAMA(4)-Cbl in cage and dissected tissues of infected and non-infected mice.

Results: Maximum binding (mean ± SD) of [(57)Co]Cbl to viable E. coli was 81.7 ± 2.6 % and to S. aureus 34.0 ± 6.7 %, at 37 °C; no binding occurred to heat-killed bacteria. Binding to both test strains was displaced by 100- to 1000-fold excess of unlabeled Cbl. The in vitro binding of [(99m)Tc]PAMA(4)-Cbl was 100-fold and 3-fold lower than the one of [(57)Co]Cbl for E. coli and S. aureus, respectively. In vivo, [(99m)Tc]PAMA(4)-Cbl showed peak percentage of injected dose (% ID) values between 1.33 and 2.3, at 30 min post-injection (p.i.). Significantly higher retention occurred in cage fluids infected with S. aureus at 4 h and with E. coli at 8 h p.i. than in non-infected animals. Accumulation into infected cages was also higher than the one of [(99m)Tc]DTPA, which showed similar biodistribution in infected and sterile mice. [(57)Co]Cbl gradually accumulated in cages with peaks % ID between 3.58 and 4.83 % achieved from 24 to 48 h. Discrimination for infection occurred only in E. coli-infected mice, at 72 h p.i. [(67)Ga]citrate, which showed a gradual accumulation into cage fluids during 12 h, was discriminative for infection from 48 to 72 h p.i. (P < 0.05).

Conclusion: Cbl displayed rapid and specific in vitro binding to test strains. [(99m)Tc]PAMA(4)-Cbl was rapidly cleared from most tissues and discriminated between sterile and infected cages, being a promising candidate for imaging infections in humans.

No MeSH data available.


Related in: MedlinePlus

Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [57Co]Cbl to aE. coli and bS. aureus at different incubation times. Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [99mTc]PAMA(4)-Cbl to cS. aureus at different incubation times. At 37 °C (closed circles, continuous line), 4 °C (open circles, dashed line), ethanol-killed bacteria (closed triangles, dotted line) and heat-killed bacteria (closed diamonds, dashed-dotted line). Note that X- and Y-axes are scaled depending on the bacterium or radiopharmaceutical tested.
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Fig3: Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [57Co]Cbl to aE. coli and bS. aureus at different incubation times. Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [99mTc]PAMA(4)-Cbl to cS. aureus at different incubation times. At 37 °C (closed circles, continuous line), 4 °C (open circles, dashed line), ethanol-killed bacteria (closed triangles, dotted line) and heat-killed bacteria (closed diamonds, dashed-dotted line). Note that X- and Y-axes are scaled depending on the bacterium or radiopharmaceutical tested.

Mentions: Binding of [57Co]Cbl to viable E. coli and S. aureus was time dependent. E. coli showed a rapid binding with plateau reached already 10 min after incubation in a temperature-independent fashion (Fig. 3a). With S. aureus, [57Co]Cbl displayed a slower binding kinetic and no plateau was reached even after 3 h of incubation (Fig. 3b). In contrast to E. coli, binding of S. aureus was temperature dependent (approximately 3-fold higher at 37 than at 4 °C). The maximum binding (mean ± SD) was measured at 37 °C and was 81.7 ± 2.6 % for E. coli and 34.0 ± 6.7 % for S. aureus. Binding of [57Co]Cbl to ethanol-killed E. coli was lower than the one observed in viable bacteria, while no binding was measured with heat-killed E. coli, whereas 5[57Co]Cbl did not show any binding to both ethanol-killed and heat-killed S. aureus.Fig. 3.


Evaluation of a Novel Tc-99m Labelled Vitamin B12 Derivative for Targeting Escherichia coli and Staphylococcus aureus In Vitro and in an Experimental Foreign-Body Infection Model.

Baldoni D, Waibel R, Bläuenstein P, Galli F, Iodice V, Signore A, Schibli R, Trampuz A - Mol Imaging Biol (2015)

Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [57Co]Cbl to aE. coli and bS. aureus at different incubation times. Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [99mTc]PAMA(4)-Cbl to cS. aureus at different incubation times. At 37 °C (closed circles, continuous line), 4 °C (open circles, dashed line), ethanol-killed bacteria (closed triangles, dotted line) and heat-killed bacteria (closed diamonds, dashed-dotted line). Note that X- and Y-axes are scaled depending on the bacterium or radiopharmaceutical tested.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4641156&req=5

Fig3: Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [57Co]Cbl to aE. coli and bS. aureus at different incubation times. Kinetic of in vitro binding (mean CPM/CPM0% ± SD) of [99mTc]PAMA(4)-Cbl to cS. aureus at different incubation times. At 37 °C (closed circles, continuous line), 4 °C (open circles, dashed line), ethanol-killed bacteria (closed triangles, dotted line) and heat-killed bacteria (closed diamonds, dashed-dotted line). Note that X- and Y-axes are scaled depending on the bacterium or radiopharmaceutical tested.
Mentions: Binding of [57Co]Cbl to viable E. coli and S. aureus was time dependent. E. coli showed a rapid binding with plateau reached already 10 min after incubation in a temperature-independent fashion (Fig. 3a). With S. aureus, [57Co]Cbl displayed a slower binding kinetic and no plateau was reached even after 3 h of incubation (Fig. 3b). In contrast to E. coli, binding of S. aureus was temperature dependent (approximately 3-fold higher at 37 than at 4 °C). The maximum binding (mean ± SD) was measured at 37 °C and was 81.7 ± 2.6 % for E. coli and 34.0 ± 6.7 % for S. aureus. Binding of [57Co]Cbl to ethanol-killed E. coli was lower than the one observed in viable bacteria, while no binding was measured with heat-killed E. coli, whereas 5[57Co]Cbl did not show any binding to both ethanol-killed and heat-killed S. aureus.Fig. 3.

Bottom Line: The in vitro binding of [(99m)Tc]PAMA(4)-Cbl was 100-fold and 3-fold lower than the one of [(57)Co]Cbl for E. coli and S. aureus, respectively.Significantly higher retention occurred in cage fluids infected with S. aureus at 4 h and with E. coli at 8 h p.i. than in non-infected animals.Accumulation into infected cages was also higher than the one of [(99m)Tc]DTPA, which showed similar biodistribution in infected and sterile mice. [(57)Co]Cbl gradually accumulated in cages with peaks % ID between 3.58 and 4.83 % achieved from 24 to 48 h.

View Article: PubMed Central - PubMed

Affiliation: Infectious Diseases Research Laboratory, Department of Biomedicine, University Hospital, Basel, Switzerland.

ABSTRACT

Purpose: Vitamin B12 (cyanocobalamin, Cbl) is accumulated by rapidly replicating prokaryotic and eukaryotic cells. We investigated the potential of a Tc-99m labelled Cbl derivative ([(99m)Tc]PAMA(4)-Cbl) for targeting infections caused by Escherichia coli and Staphylococcus aureus. In vitro binding assays were followed by biodistribution studies in a mouse model of foreign body infection.

Procedures: E. coli (ATCC 25922) and S. aureus (ATCC 43335) were used as test strains. [(57)Co]Cbl, [(67)Ga]citrate and [(99m)Tc]DTPA served as reference compounds. The in vitro competitive binding of [(57)Co]Cbl or [(99m)Tc]PAMA(4)-Cbl, and unlabeled Cbl, to viable or killed bacteria, was evaluated at 37 and 4 °C. A cage mouse model of infection was used for biodistribution of intravenous [(57)Co]Cbl and [(99m)Tc]PAMA(4)-Cbl in cage and dissected tissues of infected and non-infected mice.

Results: Maximum binding (mean ± SD) of [(57)Co]Cbl to viable E. coli was 81.7 ± 2.6 % and to S. aureus 34.0 ± 6.7 %, at 37 °C; no binding occurred to heat-killed bacteria. Binding to both test strains was displaced by 100- to 1000-fold excess of unlabeled Cbl. The in vitro binding of [(99m)Tc]PAMA(4)-Cbl was 100-fold and 3-fold lower than the one of [(57)Co]Cbl for E. coli and S. aureus, respectively. In vivo, [(99m)Tc]PAMA(4)-Cbl showed peak percentage of injected dose (% ID) values between 1.33 and 2.3, at 30 min post-injection (p.i.). Significantly higher retention occurred in cage fluids infected with S. aureus at 4 h and with E. coli at 8 h p.i. than in non-infected animals. Accumulation into infected cages was also higher than the one of [(99m)Tc]DTPA, which showed similar biodistribution in infected and sterile mice. [(57)Co]Cbl gradually accumulated in cages with peaks % ID between 3.58 and 4.83 % achieved from 24 to 48 h. Discrimination for infection occurred only in E. coli-infected mice, at 72 h p.i. [(67)Ga]citrate, which showed a gradual accumulation into cage fluids during 12 h, was discriminative for infection from 48 to 72 h p.i. (P < 0.05).

Conclusion: Cbl displayed rapid and specific in vitro binding to test strains. [(99m)Tc]PAMA(4)-Cbl was rapidly cleared from most tissues and discriminated between sterile and infected cages, being a promising candidate for imaging infections in humans.

No MeSH data available.


Related in: MedlinePlus