Usefulness of 99mTc-ciprofloxacin scintigraphy in the diagnosis of prosthetic joint infections. Nucl Med Commun. 2011;32:44-51. [PMID: 20975609 DOI: 10.1097/MNM.0b013e328340e6fb]

Leukocyte scintigraphy has high specificity but low sensitivity in diagnosing persistent periprosthetic joint infection before reimplantation in two-stage revision

INTRODUCTION

Two-stage revision is considered the gold standard treatment in chronic periprosthetic joint infection (PJI) but no specific criteria or examination exist to determine infection eradication before reimplantation. This study aimed to assess the diagnostic performance of leukocyte scintigraphy after the first-stage procedure in two-stage revision for chronic PJI.

MATERIAL AND METHODS

Patients studied with leukocyte scintigraphy after cement spacer insertion for knee PJI from January 2012 to December 2021 were retrospectively included. Infection was diagnosed using the criteria of the 2018 International Consensus Meeting. When 1 or more minor criteria were positive but the score was < 6, patients were considered not infected if there was no recurrence of infection at least 24 months after the second-stage procedure. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were found.

RESULTS

The final cohort included 67 cases in 61 patients (M: F = 32:35; mean age 74 years). There were 43 true negatives, 8 true positives, 12 false negatives, and 4 false positives. The sensitivity and specificity of leukocyte scintigraphy in diagnosing PJI were respectively 40.0% and 91.5%, PPV was 66.7%, NPV was 78.2%, and accuracy was 76.1%. Staphylococcus Epidermidis was the most frequently isolated microorganism (50%).

CONCLUSION

Due to the high costs and the difficulty in its execution, LLS should not be used routinely but it could represent an additional criterion in doubtful cases. In any case, a thorough evaluation of other pre- and intra-operative tests is essential to determine whether reimplantation or spacer renewal is the best course of action. Special consideration should be given to positive LLS, as its results are highly specific and have a low rate of false positives. Conversely, in over half of infected patients, LLS could give false negatives, making negative LLS results less relevant.

Alternatives for the Detection and Diagnosis of Osteoarticular Infections: An Exploratory Review

The precise diagnosis of osteomyelitis, a bone infection, remains a significant challenge for healthcare professionals. This difficulty stems from the highly variable nature of its clinical presentation and disease course. Patients can exhibit a wide range of symptoms, making it easy to misdiagnose the condition. In turn, inaccurate diagnoses lead to inappropriate treatment regimens, potentially hindering a patient's recovery and causing unnecessary complications. Nuclear medicine offers a ray of hope in this fight against diagnostic ambiguity. It provides valuable tools, such as radiopharmaceutical imaging, that can significantly improve the accuracy of osteomyelitis diagnosis. However, limitations exist. This article explores the need for alternative diagnostic approaches within the specific context of Costa Rica. This exploration is particularly relevant due to the current regional shortage of gallium-67 (⁶⁷Ga), a radiopharmaceutical commonly used in osteomyelitis diagnosis. The article delves into the nature, function, and limitations of various nuclear medicine techniques, encompassing both independent radiopharmaceuticals like ⁶⁷Ga and those conjugated with specific targeting molecules to pinpoint areas of infection within the body. Given the scarcity of ⁶⁷Ga in Costa Rica, it becomes crucial to explore and implement viable alternative diagnostic techniques within the healthcare system. This article emphasizes the need for further investigation into these alternatives, with the goal of improving diagnostic accuracy and ensuring optimal patient care. By implementing these alternatives, healthcare professionals in Costa Rica can effectively combat the challenges posed by osteomyelitis and pave the way for better patient outcomes.

The Development and Validation of Radiopharmaceuticals Targeting Bacterial Infection

The International Atomic Energy Agency organized a technical meeting at its headquarters in Vienna, Austria, in 2022 that included 17 experts representing 12 countries, whose research spanned the development and use of radiolabeled agents for imaging infection. The meeting focused largely on bacterial pathogens. The group discussed and evaluated the advantages and disadvantages of several radiopharmaceuticals, as well as the science driving various imaging approaches. The main objective was to understand why few infection-targeted radiotracers are used in clinical practice despite the urgent need to better characterize bacterial infections. This article summarizes the resulting consensus, at least among the included scientists and countries, on the current status of radiopharmaceutical development for infection imaging. Also included are opinions and recommendations regarding current research standards in this area. This and future International Atomic Energy Agency-sponsored collaborations will advance the goal of providing the medical community with innovative, practical tools for the specific image-based diagnosis of infection.

Physicochemical and Biological Study of 99mTc and 68Ga Radiolabelled Ciprofloxacin and Evaluation of [99mTc]Tc-CIP as Potential Diagnostic Radiopharmaceutical for Diabetic Foot Syndrome Imaging

This paper presents the application of ciprofloxacin as a biologically active molecule (vector) for delivering diagnostic radiopharmaceuticals to the sites of bacterial infection. Ciprofloxacin-based radioconjugates containing technetium-99m or gallium-68 radionuclides were synthesised, and their physicochemical (stability, lipophilicity) and biological (binding study to Staphylococcus aureus and Pseudomonas aeruginosa) properties were investigated. Both the tested radiopreparations met the requirements for radiopharmaceuticals, and technetium-99m-labelled ciprofloxacin turned out to be a good radiotracer for the tomography of diabetic foot syndrome using SPECT.

Nuclear Medicine Scans in Total Joint Replacement

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A 3-phase bone scan is a potential first-line nuclear medicine study for pain after total joint arthroplasty (TJA) when there is concern for periprosthetic joint infection or aseptic loosening.

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In patients who have a positive bone scintigraphy result and suspected infection of the joint, but where aspiration or other studies are inconclusive, labeled leukocyte scintigraphy with bone marrow imaging may be of benefit.

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Magnetic resonance imaging (MRI), while not a nuclear medicine study, also shows promise and has the advantage of providing information about the soft tissues around a total joint replacement.

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Radiotracer uptake patterns in scintigraphy are affected by the prosthesis (total knee arthroplasty [TKA] versus total hip arthroplasty [THA]) and the use of cement.

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Nuclear medicine scans may be ordered 1 year postoperatively but may have positive findings that are due to normal physiologic bone remodeling. Nuclear studies may be falsely positive for up to 2 years after TJA.

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Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) (SPECT/CT), fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT, and MRI show promise; however, more studies are needed to better define their role in the diagnostic workup of pain after TJA.

High Enantiomeric Excess In-Loop Synthesis of d-[methyl-11C]Methionine for Use as a Diagnostic Positron Emission Tomography Radiotracer in Bacterial Infection

Currently, there exists no accurate, noninvasive clinical imaging method to detect living bacteria in vivo. Our goal is to provide a positron emission tomography (PET) method to image infection by targeting bacteria-specific metabolism. Standard of care methodologies detect morphologic changes, image immunologic response to infection, or employ invasive tissue sampling with associated patient morbidity. These strategies, however, are not specific for living bacteria and are often inadequate to detect bacterial infection during fever workup. As such, there is an unmet clinical need to identify and validate new imaging tools suitable for noninvasive, in vivo (PET) imaging of living bacteria. We have shown that d-[methyl-¹¹C]methionine (d-[¹¹C]Met) can distinguish active bacterial infection from sterile inflammation in a murine infection model and is sensitive to both Gram-positive and Gram-negative bacteria. Here, we report an automated and >99% enantiomeric excess (ee) synthesis of d-[¹¹C]Met from a linear d-homocysteine precursor, a significant improvement over the previously reported synthesis utilizing a d-homocysteine thiolactone hydrochloride precursor with approximately 75-85% ee. Furthermore, we took additional steps toward applying d-[¹¹C]Met to infected patients. d-[¹¹C]Met was subject to a panel of clinically relevant bacterial strains and demonstrated promising sensitivity to these pathogens. Finally, we performed radiation dosimetry in a normal murine cohort to set the stage for translation to humans in the near future.

Susceptibility of 99mTc-Ciprofloxacin for Common Infection Causing Bacterial Strains Isolated from Clinical Samples: an In Vitro and In Vivo Study

^99mTc-ciprofloxacin scintigraphy is useful in the detection of gram-positive and gram-negative bacterial infections and also for differentiating the infection from aseptic inflammation. However, due to growing bacterial resistance to antibiotics, the ^99mTc-ciprofloxacin no longer can be effective in broad-spectrum infection imaging as it is gradually losing specificity. In this study, we are presenting our findings regarding the in vitro and in vivo susceptibility of ^99mTc-ciprofloxacin for multi-drug-resistant Staphylococcus aurous, Escherichia coli, and Pseudomonas aeruginosa bacterial strains which were isolated from clinical samples. The results of radiosynthesis of ^99mTc-ciprofloxacin showed more the 95% radiochemical purity and less than 5% radioactive impurities. In vitro ^99mTc-ciprofloxacin susceptibility test showed that E. coli offered more resistant to ^99mTc-ciprofloxacin as compared to S. aurous and P. aeruginosa. In vivo study using bacterial infection induced rabbit model also revealed lowest uptake by E. coli lesion. The T/NT values were obtained 1.96 ± 0.15 in the case of E. coli; 2.81 ± 0.51 in the case of S. aurous; and 2.32 ± 0.66 in the case of P. aeruginosa at 4 h post-injection. The SPECT infection imaging of S. aurous, E. coli, and P. aeruginosa bacterial infection induced rabbit models also indicated the clear accumulation in S. aurous and P. aeruginosa lesions while negligible uptake by E. coli lesion further verify the in vitro and in vivo susceptibility profile. On the bases of the results obtained, the ^99mTc-ciprofloxacin showed selective and poor broad spectrum SPECT infection imaging.

Ciprofloxacin: from infection therapy to molecular imaging

Diagnosis of deep-seated bacterial infection remains a serious medical challenge. The situation is becoming more severe with the increasing prevalence of bacteria that are resistant to multiple antibiotic classes. Early efforts to develop imaging agents for infection, such as technetium-99m (^99mTc) labeled leukocytes, were encouraging, but they failed to differentiate between bacterial infection and sterile inflammation. Other diagnostic techniques, such as ultrasonography, magnetic resonance imaging, and computed tomography, also fail to distinguish between bacterial infection and sterile inflammation. In an attempt to bypass these problems, the potent, broad-spectrum antibiotic ciprofloxacin was labeled with ^99mTc to image bacterial infection. Initial results were encouraging, but excitement declined when controversial results were reported. Subsequent radiolabeling of ciprofloxacin with ^99mTc using tricarbonyl and nitrido core, fluorine and rhenium couldn't produce robust infection imaging agent and remained in discussion. The issue of developing a robust probe can be approached by reviewing the broad-spectrum activity of ciprofloxacin, labeling strategies, potential for imaging infection, and structure-activity (specificity) relationships. In this review we discuss ways to accelerate efforts to improve the specificity of ciprofloxacin-based imaging.

3-phase Technicium-99m bone scanning in patients with pain in the hip region after cemented total hip replacement: a multicentre series of 100 cases

INTRODUCTION

The aim of this study was to assess the benefit of a Technetium-99M (HDP) 3-phase bone scan (TPBS) as an additional diagnostic test in the evaluation of pain in the hip region following cemented total hip replacement (THR) surgery.

METHODS

A retrospective study over a 24-month period was performed comprising 100 patients investigated with a TPBS. Investigations were summarised and analysed, and were classified as entirely normal, possibly abnormal, and definitely abnormal.

RESULTS

45% (45) of TPBSs were reported as being entirely normal, 50% (50) as possibly abnormal, and 5% (5) as definitely abnormal. During the 24-month study period 230 revision THR procedures were performed at our institution; 10% (24) were investigated with TPBS and 90% (206) were not. 29% (7/24) of patients investigated with a TPBS that subsequently underwent revision THR surgery had an entirely normal preoperative TPBS. 84% (38) with an abnormal TPBS were managed conservatively. A TPBS had a sensitivity of 29% (95% confidence interval (CI), 13%-51%) and a specificity of 50% (95% CI, 38%-62%) in the detection of infection, or loosening with concurrent infection.

CONCLUSION

A TPBS should only be considered following clinical evaluation, serological investigation, diagnostic imaging and microbiological analysis of fluid obtained from arthrocentesis by a specialist revision arthroplasty surgeon. A TPBS may be useful in the situation where abnormal serology is present, but where repeated joint aspirations samples are inconclusive.

Currently Available Radiopharmaceuticals for Imaging Infection and the Holy Grail

Infection is ubiquitous. However, its management is challenging for both the patients and the health-care providers. Scintigraphic imaging of infection dates back nearly half a century. The advances in our understanding of the pathophysiology of disease at cellular and molecular levels have paved the way to the development of a large number of radiopharmaceuticals for scintigraphic imaging of infection. These include radiolabeling of blood elements such as serum proteins, white blood cells (WBCs), and cytokines, to name a few. Infectious foci have also been imaged using a radiolabeled sugar molecule by taking advantage of increased metabolic activity in the infectious lesions. Literature over the years has well documented that none of the radiopharmaceuticals and associated procedures that facilitate imaging infection are flawless and acceptable without a compromise. As a result, only a few compounds such as 99mTc-hexamethylpropyleneamineoxime, 18F-FDG, the oldest but still considered as a gold standard 111In-oxine, and, yes, even 67Ga-citrate in some countries, have remained in routine clinical practice. Nonetheless, the interest of scientists and physicians to improve the approaches to imaging and to the management of infection is noteworthy. These approaches have paved the way for the development of numerous, innovative radiopharmaceuticals to label autologous WBCs ex vivo or even those that could be injected directly to image infection or inflammation without direct involvement of WBCs. In this review, we briefly describe these agents with their pros and cons and place them together for future reference.

Fluoroquinolones as imaging agents for bacterial infection

Diagnosis of deep-seated bacterial infection is difficult, as neither standard anatomical imaging nor radiolabeled, autologous leukocytes distinguish sterile inflammation from infection. Two recent imaging efforts are receiving attention: (1) radioactive derivatives of sorbitol show good specificity with Gram-negative bacterial infections, and (2) success in combining anatomical and functional imaging for cancer diagnosis has rekindled interest in 99mTc-fluoroquinolone-based imaging. With the latter, computed tomography (CT) would be combined with single-photon-emission-computed tomography (SPECT) to detect 99mTc-fluoroquinolone-bacterial interactions. The present minireview provides a framework for advancing fluoroquinolone-based imaging by identifying gaps in our understanding of the process. One issue is the reliance of 99mTc labeling on the reduction of sodium pertechnetate, which can lead to colloid formation and loss of specificity. Specificity problems may be reduced by altering the quinolone structure (for example, switching from ciprofloxacin to sitafloxacin). Another issue is the uncharacterized nature of 99mTc-ciprofloxacin binding to, or sequestration in, bacteria: specific interactions with DNA gyrase, an intracellular fluoroquinolone target, are unlikely. Labeling with 68Ga rather than 99mTc enables detection by positron emission tomography, but with similar biological uncertainties. Replacing the C6-F of the fluoroquinolone with 18F provides an alternative to pertechnetate and gallium that may lead to imaging based on drug interactions with gyrase. Gyrase-based imaging requires knowledge of fluoroquinolone action, which we update. We conclude that quinolone-based probes show promise for the diagnosis of infection, but improvements in specificity and sensitivity are needed. These improvements include the optimization of the quinolone structure; such chemistry efforts can be accelerated by refining microbiological assays.

Imaging Active Infection in vivo Using D-Amino Acid Derived PET Radiotracers

Occult bacterial infections represent a worldwide health problem. Differentiating active bacterial infection from sterile inflammation can be difficult using current imaging tools. Present clinically viable methodologies either detect morphologic changes (CT/ MR), recruitment of immune cells (¹¹¹In-WBC SPECT), or enhanced glycolytic flux seen in inflammatory cells (¹⁸F-FDG PET). However, these strategies are often inadequate to detect bacterial infection and are not specific for living bacteria. Recent approaches have taken advantage of key metabolic differences between prokaryotic and eukaryotic organisms, allowing easier distinction between bacteria and their host. In this report, we exploited one key difference, bacterial cell wall biosynthesis, to detect living bacteria using a positron-labeled D-amino acid. After screening several ¹⁴C D-amino acids for their incorporation into E. coli in culture, we identified D-methionine as a probe with outstanding radiopharmaceutical potential. Based on an analogous procedure to that used for L-[methyl-¹¹C]methionine ([¹¹C] L-Met), we developed an enhanced asymmetric synthesis of D-[methyl-¹¹C]methionine ([¹¹C] D-Met), and showed that it can rapidly and selectively differentiate both E. coli and S. aureus infections from sterile inflammation in vivo. We believe that the ease of [¹¹C] D-Met radiosynthesis, coupled with its rapid and specific in vivo bacterial accumulation, make it an attractive radiotracer for infection imaging in clinical practice.

Bone scan in painful knee arthroplasty: obsolete or actual examination?

ptic loosening, instability and infection are the major causes of TKA failure. For many years, nuclear medicine (NM) imaging was helpful to frame a painful total joint arthroplasty. The differentiation of septic from aseptic prosthetic loosening is critical. The latest AAOS guidelines to detect periprosthetic joint infection (PJI) restrict the role of NM scintigraphy. On the other hand, several studies suggest that NM imaging plays an important role in the evaluation of patients with painful prosthesis, but its specificity in differentiating aseptic loosening from infection is low. Moreover, scintigraphic exams showed different diagnostic accuracy in TKA compared to total hip arthroplasty (THA).

PURPOSE

To assess and discuss current knowledges about the diagnostic value of the various scans in TKA failure alone.

METHODS

We perform a pubmed/medline search to identify all papers published in the literature matching the following key words: "total knee arthroplasty", "bone", "scintigraphy", "imaging", "three-phase", "triple-phase", "99mTc-HDP", "99mTc-MDP", "99mTc-hydroxymethane diphosphonate", and "99m Tc-methylenediphosphonate", "leukocyte scanning", "labeled leukocyte scintigraphy", "antigranulocyte", "nuclear medicine", "septic loosening", "aseptic loosening" and "infection".

RESULTS

Three phases bone scintigraphy results an early diagnostic screening test or part of the preoperative tests for painful TKA and when PJI is suspected. Instead, leukocyte/bone marrow scintigraphy is superior to other scintigraphic tools in diagnosis of TKA infections. Granulocyte scintigraphy, seems to be an excellent choice when the diagnosis is unclear. Moreover, nuclear diagnostic tests showed different diagnostic accuracy between TKA and THA.

CONCLUSIONS

Although nuclear diagnostic tests for THA failure are superior in  diagnostic accuracy compared to TKA, NM scintigraphy is still an effective tool in the identification of chronic, low grade PJI. To date, scintigraphic exams have an higher levels of sensitivity, specificity and accuracy. Currently, leukocyte/bone marrow scintigraphy is considered the gold standard for this aim.  Nevertheless, further studies are needed to assess and improve the accuracy of the scintigraphic exams in order to discriminate the causes of failure for painful TKA.

What is the Accuracy of Nuclear Imaging in the Assessment of Periprosthetic Knee Infection? A Meta-analysis

BACKGROUND

In the assessment of possible periprosthetic knee infection, various imaging modalities are used without consensus regarding the most accurate technique.

QUESTIONS/PURPOSES

To perform a meta-analysis to compare the accuracy of various applied imaging modalities in the assessment of periprosthetic knee infection.

METHODS

A systematic review and meta-analysis was conducted with a comprehensive search of MEDLINE and Embase^® in accordance with the PRISMA and Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) recommendations to identify clinical studies in which periprosthetic knee infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiologic and histologic analyses, intraoperative findings, and clinical followup of more than 6 months. A total of 23 studies, published between 1990 and 2015, were included for meta-analysis, representing 1027 diagnostic images of symptomatic knee prostheses. Quality of the included studies showed low concerns regarding external validity, whereas internal validity indicated more concerns regarding the risk of bias. The most important concerns were found in the lack of uniform criteria for the diagnosis of a periprosthetic infection and the flow and timing of the included studies. Differences among techniques were tested at a probability less than 0.05 level. Where there was slight overlap of confidence intervals for two means, it is possible for the point estimates to be statistically different from one another at a probability less than 0.05. The z-test was used to statistically analyze differences in these situations.

RESULTS

Bone scintigraphy was less specific than all other modalities tested (56%; 95% CI, 0.47-0.64; p < 0.001), and leukocyte scintigraphy (77%; 95% CI, 0.69-0.85) was less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p < 0.001) or combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Fluorodeoxyglucose positron emission tomography (FDG-PET) (84%; 95% CI, 0.76-0.90) was more specific than bone scintigraphy (56%; 95% CI, 0.47-0.64; p < 0.001), and less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p = 0.02) and combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Leukocyte scintigraphy (88%; 95% CI, 0.81-0.93; p = 0.01) and antigranulocyte scintigraphy (90%; 95% CI, 0.78-0.96; p = 0.02) were more sensitive than FGD-PET (70%; 95% CI, 0.56-0.81). However, because of broad overlapping of confidence intervals, no differences in sensitivity were observed among the other modalities, including combined bone scintigraphy (93%; 95% CI, 0.85-0.98) or combined leukocyte and bone marrow scintigraphy (80%; 95% CI, 0.66-0.91; p > 0.05 for all paired comparisons).

CONCLUSIONS

Based on current evidence, antigranulocyte scintigraphy and combined leukocyte and bone marrow scintigraphy appear to be highly specific imaging modalities in confirming periprosthetic knee infection. Bone scintigraphy was a highly sensitive imaging technique but lacks the specificity needed to differentiate among various conditions that cause painful knee prostheses. FDG-PET may not be the preferred imaging modality because it is more expensive and not more effective in confirming periprosthetic knee infection.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Imaging bacteria with radiolabelled quinolones, cephalosporins and siderophores for imaging infection: a systematic review

Bacterial infections are still one of the main causes of patient morbidity and mortality worldwide. Nowadays, many imaging techniques, like computed tomography or magnetic resonance imaging, are used to identify inflammatory processes, but, although they recognize anatomical modifications, they cannot easily distinguish bacterial infective foci from non bacterial infections. In nuclear medicine, many efforts have been made to develop specific radiopharmaceuticals to discriminate infection from sterile inflammation. Several compounds (antimicrobial peptides, leukocytes, cytokines, antibiotics…) have been radiolabelled and tested in vitro and in vivo, but none proved to be highly specific for bacteria. Indeed factors, including the number and strain of bacteria, the infection site, and the host condition may affect the specificity of tested radiopharmaceuticals. Ciprofloxacin has been proposed and intensively studied because of its easy radiolabelling method, broad spectrum, and low cost, but at the same time it presents some problems such as low stability or the risk of antibiotic resistance. Therefore, in the present review studies with ciprofloxacin and other radiolabelled antibiotics as possible substitutes of ciprofloxacin are reported. Among them we can distinguish different classes, such as cephalosporins, fluoroquinolones, inhibitors of nucleic acid synthesis, inhibitors of bacterial cell wall synthesis and inhibitors of protein synthesis; then also others, like siderophores or maltodextrin-based probes, have been discussed as bacterial infection imaging agents. A systematic analysis was performed to report the main characteristics and differences of each antibiotic to provide an overview about the state of the art of imaging infection with radiolabelled antibiotics.

Imaging for infection: from visualization of inflammation to visualization of microbes

BACKGROUND

With the development of high-resolution cross-sectional imaging, anatomic identification of most areas of infection has become routine. Imaging a site of infection allows for diagnosis and treatment. In the past, molecular imaging for infection involved mainly the use of radiolabeled leukocytes for functional targeting at infection sites. With the recent development of functional nuclear imaging, bacterial and viral metabolism can also be imaged directly for potential identification of early infection.

METHODS

Review of pertinent English-language literature.

RESULTS

Cross-sectional imaging is used routinely to identify and treat sources of infection in patients with fever, leukocytosis, or unexplained hemodynamic instability. Although ultrasound is preferred for the identification of biliary or hepatic sepsis, computed tomography (CT) has proved to be accurate for the identification and treatment of intra-abdominal fluid collections and abscesses. Biologic imaging is a non-invasive technique that identifies sites of infection in cases in which no definite abnormality is identified via cross-sectional imaging. This is made possible by imaging the accumulation of radioisotopes that have been attached to white blood cells or glucose. Biologic imaging is useful for the identification of anatomic sites where there is inflammation or high metabolic demand. However, a drawback of biologic imaging is that it is not specific for infection. Techniques that image microbes directly increase the specificity of imaging results significantly and can be used to quantify and track infectious processes. For example, radiolabeling of antimicrobial proteins and antibiotics is one technique that has been demonstrated to identify areas of infection accurately in animals but is not currently being used clinically in humans. With the advent of gene therapy, many researchers are inserting the herpes viral thymidine kinase gene into both viruses and bacteria. This allows for tracking of the infectious process by imaging the accumulation of radiolabeled thymidine analogues.

CONCLUSION

This review summarizes standard imaging for infection as it is currently practiced clinically. We will also explore the promising new methods of microbial imaging that are likely to become standards in clinical care in the near future.

Diagnosis of Periprosthetic Joint Infection: The Role of Nuclear Medicine May Be Overestimated

Although the International Consensus Meeting on Periprosthetic Joint Infection's definition of periprosthetic joint infection (PJI) does not include nuclear imaging as part of the diagnostic criteria, many contemporary nuclear imaging studies are reporting exceptional results in PJI diagnosis. We conducted a systematic review of studies published from 2004 to 2012 reporting the accuracy of nuclear imaging for diagnosis of PJI, utilizing a specially designed tool (QUADAS-2) for critical appraisal and investigation of bias. Our results revealed high risk of bias as well as high levels of concern regarding the clinical applicability of these tests in a majority of the studies. On the basis of our findings, we recommend that the use of nuclear imaging for diagnosis of PJI be limited to a few select cases.

Antimicrobial activity of gentamicin and vancomycin combination in joint fluids after antibiotic-loaded cement spacer implantation in two-stage revision surgery

Gentamicin (G) and vancomycin (V) concentrations in joints fluids obtained from patients during the first 24 hours after implantation of antibiotic-loaded polymethylmethacrylate (PMMA) spacers in two-stage revision for infected arthroplasty, and the inhibitory activity of joint fluids against different multiresistant clinical isolates were studied. A total of 12 patients undergoing two-stage revision surgery with implantation of industrial G spacers added with different amounts of V was studied. Serum and joint fluid samples were collected 1, 4, and 24 hours after spacer implantation. Antibiotics concentrations and joint bactericidal titer (JBT) of combination were determined against multiresistant staphylococcal strains. The local release of G and V from PMMA cement seemed prompt and effective. Serum levels were below the limit of detection. The same joint fluid showed different activity according to the susceptibility of the pathogens tested. Gentamicin and V were released from spacers at bactericidal concentrations exerting a strong inhibition against methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (CoNS) strains.

Release of gentamicin and vancomycin from preformed spacers in infected total hip arthroplasties: measurement of concentrations and inhibitory activity in patients' drainage fluids and serum

Gentamicin (G) and vancomycin (V) concentrations in drainage fluids obtained from patients during the first 24 hours after implantation of antibiotic-loaded polymethylmethacrylate (PMMA) spacers in two-stage revision of infected total hip arthroplasty were studied. The inhibitory activity of drainage fluids against different multiresistant clinical isolates was investigated as well. Seven hips were treated by implantation of industrial G-loaded spacers. Vancomycin was added by manually mixing with PMMA bone cement. Serum and drainage fluid samples were collected 1, 4, and 24 hours after spacer implantation. Antibiotics concentrations and drains bactericidal titer of combination were determined against multiresistant staphylococcal strains. The release of G and V from PMMA cement at the site of infection was prompt and effective. Serum levels were below the limit of detection. The local release kinetics of G and V from PMMA cement was similar, exerting a pronounced, combined inhibitory effect in the implant site. The inhibitory activity of drainage fluids showed substantial intersubject variability related to antibiotic concentrations and differed according to the pathogens tested. Gentamicin and vancomycin were released from temporary hip spacers at bactericidal concentrations, and their use in combination exerted strong inhibition against methicillin-resistant S. aureus and Coagulase Negative Staphylococci strains.

Infective severe acute pancreatitis: A comparison of 99mTc-ciprofloxacin scintigraphy and computed tomography

AIM: To evaluate ^99mTc-ciprofloxacin scintigraphy compared with computed tomography (CT) for detecting secondary infections associated with severe acute pancreatitis (SAP) in swine.

METHODS: Six healthy swine were assigned to a normal control group (group A, n = 6). SAP was induced in group B (n = 9) and C (n = 18), followed by inoculation of the resulting pancreatic necroses with inactive Escherichia coli (E. coli) (group B) and active E. coli (group C), respectively. At 7 d after inoculation, a CT scan and a series of analyses using infecton imaging (at 0.5, 1, 2, 3, 4 and 6 h after the administration of 370 MBq of intravenous infecton) were performed. The scintigrams were visually evaluated and semi-quantitatively analyzed using region of interest assignments. The differences in infecton uptake and changes in the lesion-background radioactive count ratios (L/B) in the 3 groups were recorded and compared. After imaging detection, histopathology and bacterial examinations were performed, and infected SAP was regarded as positive. The imaging findings were compared with histopathological and bacteriological results.

RESULTS: In group A, 6 animals survived without infection in the pancreas. In group B, 7/9 swine survived and one suffered from infection. In group C, 15/18 animals survived with infection. Hence, the number of normal, non-infected and infected SAP swine was 6, 6 and 16, respectively. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of the infecton method were 93.8% (15/16), 91.7% (11/12), 92.9% (26/28), 93.8% (15/16) and 91.7% (11/12), whereas these values for CT were 12.5% (2/16), 100.0% (12/12), 50.0% (14/28), 100.0% (2/2) and 46.2% (12/26), respectively. The changes in L/B for the infected SAP were significantly different from those of the non-infected and normal swine (P < 0.001). The mean L/B of the infectious foci at 0.5, 1, 2, 3, 4 and 6 h was 1.17 ± 0.10, 1.71 ± 0.30, 2.46 ± 0.45, 3.36 ± 0.33, 2.04 ± 0.37 and 1.1988 ± 0.09, respectively. At 3 h, the radioactive counts (2350.25 ± 602.35 k) and the mean L/B of the infectious foci were significantly higher than that at 0.5 h (P = 0.000), 1 h (P = 0.000), 2 h (P = 0.04), 4 h (P = 0.000) and 6 h (P = 0.000).

CONCLUSION: ^99mTc-ciprofloxacin scintigraphy may be an effective procedure for detecting SAP secondary infections with higher sensitivity and accuracy than CT.

One-stage revision arthroplasty for infected hip replacements

Infection remains a serious complication after total hip arthroplasty (THA) and is a leading cause of hip revision surgery. It is currently accepted that removal of the prosthesis is essential to curing an infection when facing chronic PJIs with prosthesis loosening. In order to avoid the disadvantages of a two-stage approach, some authors have proposed a one-stage hip revision for the treatment of hip prosthesis infection in selected patients using not only antibiotic-loaded cemented components but also cementless implant. In the case of a one-stage procedure, the patient is exposed to a single major procedure and therefore lower cumulative perioperative risk. A functional prosthesis replacement is completed without exposure to the complications associated with spacers. In addition, there are also benefits both financially and in terms of resource allocation.

A preformed antibiotic-loaded spacer for treatment for septic arthritis of the shoulder

BACKGROUND

Total shoulder arthroplasty infections are rare, depending on the use of antibiotic prophylaxis, the local blood supply, the axial load gradient and the proximal location of the shoulder. The purpose of this study was to evaluate the results of treatment for infections in total shoulder arthroplasty and septic arthritis using a preformed antibiotic-loaded spacer.

MATERIALS AND METHODS

Seven shoulders in as many patients were treated for infected arthroplasty or septic arthritis without previous surgery. A preformed antibiotic-loaded spacer was always applied. Patients were evaluated at the final follow-up with the Constant Score (CS), the Secec Elbow Score (SES), and the American Shoulder and Elbow Society Score (ASESS).

RESULTS

The mean follow-up was 40, 71 months after spacer implant. Infection was always confirmed preoperatively by the leukocyte and neutrophil counts in the aspirated synovial fluid, and intra-operative biopsy and pathologic analysis. Positive bacterial cultures were found in 5 cases: 3 MRSA and 2 Staphylococcus epidermidis. The mean SES increased from 34.43 before spacer implant to 77.29 at final follow-up, ASESS ranged from 14.86 to 21.14, and CS from 40.28 to 79.14.

CONCLUSION

A preformed antibiotic-loaded spacer is intended to release gentamicin alone, but we can consider adding vancomycin to increase antibiotic spectrum. An early diagnosis and an immediate treatment can prevent a persistent infection and severe soft-tissue damage. The use of a preformed antibiotic spacer allows maintaining joint function at the intermediate stage in two-stage treatment.

Diagnosis of periprosthetic joint infections in clinical practice

The diagnosis of a periprosthetic joint infection (PJI) can be challenging, either because of the variable clinical presentation or because of previous antimicrobial treatment interfering with the detection of the pathogen. In recent years, various means to diagnose PJI have been analyzed. These include invasive and non-invasive laboratory tests, imaging procedures, and novel techniques such as sonication of implants and the use of molecular microbiology. In this review, both established and novel diagnostic procedures are presented. An algorithm for detecting PJI in patients with acute and chronic symptoms is proposed.

Prosthetic joint infections: radionuclide state-of-the-art imaging

Prosthetic joint replacement surgery is performed with increasing frequency. Overall the incidence of prosthetic joint infection (PJI) and subsequently prosthesis revision failure is estimated to be between 1 and 3%. Differentiating infection from aseptic mechanical loosening, which is the most common cause of prosthetic failure, is especially important because of different types of therapeutic management. Despite a thorough patient history, physical examination, multiple diagnostic tests and complex algorithms, differentiating PJI from aseptic loosening remains challenging. Among imaging modalities, radiographs are neither sensitive nor specific and cross-sectional imaging techniques, such as computed tomography and magnetic resonance imaging, are limited by hardware-induced artefacts. Radionuclide imaging reflects functional rather than anatomical changes and is not hampered by the presence of a metallic joint prosthesis. As a result scintigraphy is currently the modality of choice in the investigation of suspected PJI. Unfortunately, there is no true consensus about the gold standard technique since there are several drawbacks and limitations inherent to each modality. Bone scintigraphy (BS) is sensitive for identifying the failed joint replacement, but cannot differentiate between infection and aseptic loosening. Combined bone/gallium scintigraphy (BS/GS) offers modest improvement over BS alone for diagnosing PJI. However, due to a number of drawbacks, BS/GS has generally been superseded by other techniques but it still may have a role in neutropenic patients. Radiolabelled leucocyte scintigraphy remains the gold standard technique for diagnosing neutrophil-mediated processes. It seems to be that combined in vitro labelled leucocyte/bone marrow scintigraphy (LS/BMS), with an accuracy of about 90%, is currently the imaging modality of choice for diagnosing PJI. There are, however, significant limitations using in vitro labelled leucocytes and considerable effort has been devoted to developing alternative radiotracers, such as radiolabelled HIGs, liposomes, antigranulocyte antibodies and fragments, as well as more investigational tracers such as radiolabelled antibiotics, antimicrobial peptides, bacteriophages and thymidine kinase. On the other hand, positron emission tomography (PET) is still growing in the field of PJI imaging with radiotracers such as (18)F-fluorodeoxyglucose (FDG), (18)F-FDG white blood cells and (18)F-fluoride. But unfortunately this superb tomographic technique will only receive full acceptance when specific PET uptake patterns can be successfully developed. The emergence of hybrid modality imaging using integrated single photon emission computed tomography (SPECT) and PET with computed tomography (SPECT/CT and PET/CT) may also have a contributing role for more accurate assessment of joint replacement complications, especially combined with new radiotracers such as (68)Ga and (64)Cu. Finally, in searching for infection-specific tracers, currently there is no such diagnostic agent available.

The value of successive Infecton scans in assessing the presence of chronic bone and joint infection and in predicting its evolution after treatment and after a prolonged follow-up

OBJECTIVE

Our objective was to monitor the evolution of bone and/or joint infections with the aid of successive radiolabelled ciprofloxacin (Infecton) scans during antimicrobial treatment and to compare the results of an Infecton scan at the end of therapy with the respective results of clinical evaluation, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in predicting resolution or recurrence of infection after a long period of posttreatment follow-up.

METHODS

Thirty-three patients with documented bone and/or joint infection were subjected to successive Infecton scans on two or three visits. Infecton scans were evaluated visually and scored accordingly. Clinical evaluation was scored by the referring clinicians. ESR and CRP values were evaluated independently. A minimum of 2-year free-of-infection follow-up after discontinuation of the antibiotic treatment served as a measure of successful antimicrobial therapy and nonrecurrence of infection. Statistics included survival analysis (Cox regression).

RESULTS

During follow-up, five patients in the study presented with recurrence, and three died as a result of an irrelevant cause. The remaining patients were followed up for a median of 108 months (range 97-132 months) without any signs of recurrence of infection. Recurrence of infection was 4.2 times more likely to occur in patients with positive Infecton scans [hazard ratio (HR): 4.2, confidence intervals 95%: 1.39-12.67, P=0.011]. Infecton had the highest sensitivity (83.3%), accuracy (69.69%) and negative predictive value (94.74%), whereas CRP had the highest specificity (76.92%).

CONCLUSION

Infecton scintigraphy proved to be more sensitive and accurate and had a higher negative predictive value compared with clinical evaluation, ESR and CRP in predicting infection resolution or recurrence in patients with chronic bone and joint infections.