Challenges in diagnosing infection in the diabetic foot

Abstract

Diagnosing the presence of infection in the foot of a patient with diabetes can sometimes be a difficult task. Because open wounds are always colonized with microorganisms, most agree that infection should be diagnosed by the presence of systemic or local signs of inflammation. Determining whether or not infection is present in bone can be especially difficult. Diagnosis begins with a history and physical examination in which both classic and 'secondary' findings suggesting invasion of microorganisms or a host response are sought. Serological tests may be helpful, especially measurement of the erythrocyte sedimentation rate in osteomyelitis, but all (including bone biomarkers and procalcitonin) are relatively non-specific. Cultures of properly obtained soft tissue and bone specimens can diagnose and define the causative pathogens in diabetic foot infections. Newer molecular microbial techniques, which may not only identify more organisms but also virulence factors and antibiotic resistance, look very promising. Imaging tests generally begin with plain X-rays; when these are inconclusive or when more detail of bone or soft tissue abnormalities is required, more advanced studies are needed. Among these, magnetic resonance imaging is generally superior to standard radionuclide studies, but newer hybrid imaging techniques (single-photon emission computed tomography/computed tomography, positron emission tomography/computed tomography and positron emission tomography/magnetic resonance imaging) look to be useful techniques, and new radiopharmaceuticals are on the horizon. In some cases, ultrasonography, photographic and thermographic methods may also be diagnostically useful. Improved methods developed and tested over the past decade have clearly increased our accuracy in diagnosing diabetic foot infections.

Prescribing antibiotics in diabetic foot infection: what is the role of initial microscopy and culture of tissue samples?*

“…The laboratory diagnosis in DFI is evolving, with the potential for molecular techniques with high sensitivity to alter the way we understand and treat the condition . The relatively low overall sensitivity and specificity of microscopy is not altogether surprising as this technique's performance depends on the laboratory operator and the quality of the sample.…”

Stopping antibiotics after surgical amputation in diabetic foot and ankle infections—A daily practice cohort

“…We excluded amputations with no clinical signs of infection, regardless of microbiology results, mid‐tibia amputations, implant‐related DFI and patients with <2 months of active follow‐up. Osteomyelitis was diagnosed using clinical features (eg, visible bone), imaging (bone lesions without prior surgery or trauma) or microbiology (bacterial growth from surgically obtained bone specimens). We defined clinical failure as subsequent episodes of DFI occurring at the same location within 12 months.…”

Temporal Stability in Chronic Wound Microbiota Is Associated With Poor Healing

“…Microbial bioburden is believed to contribute to impaired healing of chronic wounds and it is estimated that over 50% of DFUs are infected upon presentation (Prompers et al 2007); however, infections are difficult to diagnose due to the diminished or absent clinical signs in DFUs resulting from peripheral neuropathy and/or vascular disease (Glaudemans et al 2015). Without clinical suspicion, wound cultures provide little diagnostic value, as bacteria colonize all open wounds.…”