An infected hip prosthesis in a dog diagnosed with a 99mTc-ciprofloxacin (infecton) scan

Pseudomonas spp. in Canine Otitis Externa

Canine otitis externa (OE) is a commonly diagnosed condition seen in veterinary practice worldwide. In this review, we discuss the mechanisms of the disease, with a particular focus on the biological characteristics of Pseudomonas aeruginosa and the impact that antibiotic resistance has on successful recovery from OE. We also consider potential alternatives to antimicrobial chemotherapy for the treatment of recalcitrant infections. P. aeruginosa is not a typical constituent of the canine ear microbiota, but is frequently isolated from cases of chronic OE, and the nature of this pathogen often makes treatment difficult. Biofilm formation is identified in 40-95% of P. aeruginosa from cases of OE and intrinsic and acquired antibiotic resistance, especially resistance to clinically important antibiotics, highlights the need for alternative treatments. The role of other virulence factors in OE remains relatively unexplored and further work is needed. The studies described in this work highlight several potential alternative treatments, including the use of bacteriophages. This review provides a summary of the aetiology of OE with particular reference to the dysbiosis that leads to colonisation by P. aeruginosa and highlights the need for novel treatments for the future management of P. aeruginosa otitis.

Radiochemical Approaches to Imaging Bacterial Infections: Intracellular versus Extracellular Targets

The discovery of penicillin began the age of antibiotics, which was a turning point in human healthcare. However, to this day, microbial infections are still a concern throughout the world, and the rise of multidrug-resistant organisms is an increasing challenge. To combat this threat, diagnostic imaging tools could be used to verify the causative organism and curb inappropriate use of antimicrobial drugs. Nuclear imaging offers the sensitivity needed to detect small numbers of bacteria in situ. Among nuclear imaging tools, radiolabeled antibiotics traditionally have lacked the sensitivity or specificity necessary to diagnose bacterial infections accurately. One reason for the lack of success is that the antibiotics were often chelated to a radiometal. This was done without addressing the ramifications of how the radiolabeling would impact probe entry to the bacterial cell, or the mechanism of binding to an intracellular target. In this review, we approach bacterial infection imaging through the lens of bacterial specific molecular targets, their intracellular or extracellular location, and discuss radiochemistry strategies to guide future probe development.

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.

Optical imaging of bacterial infections

The rise in multidrug resistant (MDR) bacteria has become a global crisis. Rapid and accurate diagnosis of infection will facilitate antibiotic stewardship and preserve our ability to treat and cure patients from bacterial infection. Direct in situ imaging of bacteria offers the prospect of accurately diagnosing disease and monitoring patient outcomes and response to treatment in real-time. There have been many recent advances in the field of optical imaging of infection; namely in specific probe and fluorophore design. This combined with the advances in imaging device technology render direct optical imaging of infection a feasible approach for accurate diagnosis in the clinic. Despite this, there are currently no licensed molecular probes for clinical optical imaging of infection. Here we report some of the most promising and interesting probes and approaches under development for this purpose, which have been evaluated in in vivo models within the laboratory setting.

(99M)Tc-ciprofloxacin in imaging of clinical infections in camelids and a goat

(99M)Tc-ciprofloxacin was used to image five adult camelids and a juvenile goat with clinical and/or radiographic signs of infection. (99m)Tc-ciprofloxacin (range 10-33 MBq/kg) was injected intravenously and a series of 2-min static images were acquired at 1- and 4-h postinjection. At 24-h postinjection, 5-min static images were acquired. Only the skull or abdomen was imaged in the adults; the whole body was imaged in the goat. The quality of the 1-, 4-, and 24-h studies was evaluated subjectively. Normal and abnormal areas of (99m)Tc-ciprofloxacin uptake were recorded and subjectively graded as mild, moderate or intense. Image quality was best 4-h postinjection. Twenty-four-hour images were poor because of insufficient radioactivity. (99m)Tc-ciprofloxacin imaging resulted in true positive or true negative scans in four of six animals. Two false-negative studies occurred. Intense (99m)Tc-cirofloxacin activity was seen in the lungs and urinary bladder, moderate/intense activity in the kidneys, and mild activity in the physes/epiphyses, liver and intermittently in the gastrointestinal tract. The normal distribution of (99m)Tc-ciprofloxacin in camelids/small ruminants differed from people. Further studies to determine the sensitivity and specificity of infection detection using (99m)Tc-ciprofloxacin in animals are warranted.

Bone scintigraphy in the investigation of occult lameness in the dog

99mTechnetium methylene diphosphonate (99mTc-MDP) scintigraphy was performed in 14 dogs of different breeds after clinical lameness examination, radiography and synovial fluid analysis failed to localise lameness to a specific area of pain. The scintigraphic protocol included an intravenous injection of 17 MBq 99mTc-MDP/kg bodyweight and vascular, soft tissue and bone phase scans in standardised positions with a low-energy all-purpose collimator. Confirmation of diagnosis was achieved in nine dogs by arthroscopy, repeated lesion-orientated radiography, computed tomography and response to treatment. In seven cases, bone phase scans showed single elbow uptakes, in two cases unilateral limb uptake, and in one case each a single shoulder and tibia uptake; in three cases there was no increased uptake. Vascular and soft tissue phase images did not reveal additional information. Diagnosis of humeral condyle fissures, a fragmented medial coronoid process, panosteitis and arthropathy was possible in nine cases. Skeletal pathology was ruled out in three normal scintigrams. In two dogs with unilateral uptake of multiple joints, no diagnostic benefit was gained from scintigraphy. The highly sensitive and relatively specific uptake allowed localisation and characterisation or exclusion of skeletal lesions in most dogs.