Evaluation of 99mTc-Ubiquicidin 29-41 Scintigraphyin in Differentiation of Bacterial Infection from Sterile Inflammationin Diabetic Foot

Ubiquicidin (UBI) 29-41 is a synthetic antimicrobial peptide that binds with the microbial cell membrane at the location of infection. This study was conducted to evaluate its probable efficacy as an infection-imaging agent with potential to differentiate bacterial infection from sterile inflammation in humans. Fifteen diabetic foot patients (10 males and 5 females) with suspected bacterial infection, prior to starting antibiotic treatment, were selected for this study. First a routine three phase bone scan and later a 99mTc-UBI scan was performed for all the patients. 555-740 MBq of 99mTc-UBI was injected intravenously. A 10 minute dynamic study was followed by spot views of the suspected region of infection and corresponding normal areas (liver and kidneys) at 60 and 120 min. Whole-body anterior and posterior images were also acquired. To interpret the studies as positive or negative, visual score (0 -3) was used, with scores of 0 (minimal or no uptake; equivalent to soft tissue) and 1 (mild; less uptake than in liver) being considered negative and scores of 2 (moderate; uptake equal to or greater than that in liver) and 3 (intense uptake equal to or greater than that in kidneys) being considered positive. Of 15 studies performed with 99mTc-UBI, all had positive bacterial cultures. The result of bone scan was positive for osteomyelitis in 12 patients (80%). 99mTc-UBI Scintigraphy was positive in 6 patients, but negative in nine. The sensitivity of 99mTc-UBI for detection of infection was therefore 40%. From 12 patients who had positive bone scans, only 6 had a positive 99mTc-UBI (50%) indicating the sensitivity of 50% for 99mTc-UBI in osteomyelitis cases. 99mTc-UBI was not positive in any patient who had evidence of soft tissue infection in the bone scan. Although 99mTc-UBI 29-41 was well tolerated by all the patients without any side effects, considering low sensitivity of this agent, this radiopharmaceutical is not of great value for diabetic foot infection diagnosis.