Evaluation of 99mTc-UBI 29-41 scintigraphy for specific detection of experimental Staphylococcus aureus prosthetic joint infections.
OBJECTIVE
(99m)Tc-UBI 29-41 (UBI), an antimicrobial peptide, specifically targets bacteria. We tested the ability of UBI to discriminate between infected and uninfected prosthetic joints using a rabbit model previously validated.


METHODS
Left knee arthroplasty was performed on 20 New Zealand rabbits, then 10(7) cfu of S. aureus (n = 12) or sterile saline (n = 8) was injected into the joint. On days 9 and 20 after surgery, planar UBI scintigraphy was performed in six infected and four uninfected rabbits, 1 h and 4 h p.i. (150 MBq), on a gamma camera. Operated-to-normal knee activity ratio (ONKR) was calculated on each scintigram. Then, after sacrifice, tissue samples of both knees were counted in a gamma counter.


RESULTS
One rabbit injected with sterile saline had cutaneous infection at sacrifice and was excluded from analysis. ONKR was higher in infected than in uninfected animals 4 h p.i. 20 days after surgery: 1.75 +/- 0.48 vs 1.13 +/- 0.11, p = 0.04. From 1 h to 4 h p.i., ONKR increased in 9/12 infected and 0/7 uninfected animals. According to UBI uptake intensity and kinetics, scintigraphy was truly positive in all infected cases on day 9 and in four of six infected cases on day 20. It was truly negative in two of three sterile inflamed prosthetic knees on day 9, and in all cases on day 20. Biodistribution studies revealed increased UBI uptake in periprosthetic tissues in all animals 9 days after surgery, and only in infected animals on day 20.


CONCLUSIONS
In this experimental study, (99m)Tc-UBI 29-41 scintigraphy permitted the early detection of acute prosthetic joint infection, and exclusion of infection in chronic sterile prosthetic joint inflammation.
Sarda-Mantel
Laure
L
Université Denis Diderot-Paris 7, UMR S773, F-75018 Paris, France. sarda@bichat.inserm.fr
Saleh-Mghir
Azzam
A
Welling
Mick M
MM
Meulemans
Alain
A
Vrigneaud
Jean-Marc
JM
Raguin
Olivier
O
Hervatin
Florence
F
Martet
Geneviève
G
Chau
Françoise
F
Lebtahi
Rachida
R
Le Guludec
Dominique
D
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry; D005121:Extremities / Q000000981:diagnostic imaging; D005260:Female; D015902:Gamma Cameras; D007596:Joints / Q000382:microbiology*; D015609:Organotechnetium Compounds; D010446:Peptide Fragments; D011475:Prosthesis Failure; D011817:Rabbits; D011849:Radioactive Tracers; D011877:Radionuclide Imaging / Q000379:methods*; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000378:metabolism*
D023181:Antimicrobial Cationic Peptides; D015609:Organotechnetium Compounds; D010446:Peptide Fragments; D011849:Radioactive Tracers; C485080:technetium 99m ubiquicidin(29-41)