Labeling of antibiotics for infection diagnosis.

The high impact of infection on daily clinical practice has promoted research into better and more accurate diagnostic and therapeutic methods. Localizing inflammation/infection with nuclear medicine techniques began over 40 years ago. Today, 67 Ga-scintigraphy, 9 9m Tc-nanocolloid, 111 In and 99m Tc in vitro labeled leukocytes, and monoclonal antigranulocyte antibodies are widely available for this purpose. While these methods are useful for localizing inflammation, they cannot always differentiate septic from aseptic processes. The ideal properties of an agent for diagnosing infection include: high specificity, early diagnosis, rapid blood clearance, ease of preparation, low toxicity, biodistribution appropriate for the disease under study, absence of immunologic response and low cost. A novel approach to infection diagnosis is the use of radiolabelled antibiotics. Antibiotics localize in the infectious focus, where they are frequently taken up and metabolized by microorganisms. The majority of the various antibiotics studied so far are those of the quinolones group (ciprofloxacin, sparfloxacin, enrofloxacin, levofloxacin, norfloxacin and ofloxacin). More recently, the labeling of ceftizoxime, a semisynthetic third generation cephalosporin, has been reported. The relevant features of labeled antibiotics in research and/or clinical infection diagnosis are the focus of this article.