Evaluation of (99m)Tc-ciprofloxacin scintigraphy in a rabbit model of Staphylococcus aureus prosthetic joint infection.
Ciprofloxacin, a quinolone antibiotic drug, binds to DNA topoisomerase IV and DNA gyrase of various bacteria. Thus ciprofloxacin labeled with (99m)Tc could potentially act as a specific marker allowing discrimination between infection and sterile inflammation. We evaluated these properties on a rabbit model of prosthetic joint infection previously validated. We compared the images obtained in 2 groups of animals: rabbits with infected (G1; n = 6) and uninfected (G2; n = 7) prosthesis.


METHODS
Partial right-knee arthroplasty was performed on 13 New Zealand White female rabbits, with a tibial silicone-elastomer implant fitting into the intramedullary canal of the tibia. After the surgical wound was closed, 10(7) cfu of a clinical strain of methicillin-susceptible Staphylococcus aureus were injected into the joint in G1 rabbits. G2 rabbits were injected with sterile saline. No antibiotic therapy was given to the animals. (99m)Tc-ciprofloxacin planar imaging was performed on days 5, 12, and 19 after surgery, and after 3 mo in 1 uninfected rabbit. Images were obtained 1, 4, and 24 h after injection (147 +/- 13 MBq).


RESULTS
In G1, increased right knee (99m)Tc-ciprofloxacin uptake was observed in 3 of 5 rabbits on day 5, and in all cases on days 12 and 19. Killing of the animals revealed purulent arthritis, osteitis, and tibial myelitis. In G2, significant right-knee uptake was found on days 12 and 19 in 5 of 6 rabbits, and after 3 mo in 1; all sets of images were negative in 1 animal. Bacteriologic studies after the animals were killed were negative in G2. Mean right/left knee uptake ratios on day 19 (4-h images) were 1.8 +/- 0.4 in G1 versus 1.4 +/- 0.3 in G2 (not significant). Late images did not discriminate between infected and uninfected arthroplasty.


CONCLUSIONS
Results of (99m)Tc-ciprofloxacin imaging in rabbits with infected/uninfected knee prosthesis suggest good sensitivity but lack of specificity for the detection of S. aureus infection.
Sarda
Laure
L
Service Hospitalier Frédéric Joliot, CEA, Orsay, France.
Saleh-Mghir
Azzam
A
Peker
Can
C
Meulemans
Alain
A
Crémieux
Anne-Claude
AC
Le Guludec
Dominique
D
D000818:Animals; D000890:Anti-Infective Agents / Q000493:pharmacokinetics; D001345:Autoradiography; D002939:Ciprofloxacin / Q000493:pharmacokinetics; D005260:Female; D007719:Knee Joint / Q000000981:diagnostic imaging*; D007720:Knee Prosthesis / Q000009:adverse effects*; D016459:Prosthesis-Related Infections / Q000000981:diagnostic imaging*; D011817:Rabbits; D011877:Radionuclide Imaging; D013203:Staphylococcal Infections / Q000000981:diagnostic imaging*; D013667:Technetium / Q000493:pharmacokinetics; D014018:Tissue Distribution
D000890:Anti-Infective Agents; D002939:Ciprofloxacin; D013667:Technetium