Understanding the microbiome of diabetic foot osteomyelitis: insights from molecular and microscopic approaches

Type 2 diabetes mediates the causal relationship between obesity and osteomyelitis: A Mendelian randomization study

Mendelian randomization (MR) analysis was used to determine the causal relationship between Type 2 diabetes (T2D) and osteomyelitis (OM). We performed MR analysis using pooled data from different large-scale genome-wide association studies (GWAS). Instrumental variables were selected based on genome-wide significance, instrumental strength was assessed using F-values, and thresholds for the number of exposed phenotypes were further adjusted by Bonferroni correction. univariable and multivariable MR analyses were performed to assess causal effects and proportions mediated by T2D. IVW (inverse variance weighting) showed a significant genetic effect of osteomyelitis on the following: After correction by Bonferroni, univariable analyses showed that childhood body mass index (BMI) was not significantly associated with genetic susceptibility to OM [odds ratio (OR), 1.26; 95% confidence interval (CI), 1.02, 1.55; P = .030], not significantly associated with adulthood BMI (OR, 1.28; 95% CI, 1.02, 1.61; P = .034), significantly associated with waist circumference (OR, 1.84; 95% CI, 1.51, 2.24; P < .001), and significantly associated with hip circumference (OR, 1.52; 95% CI, 1.31, 1.76; P < .001). Meanwhile, multivariable analyses showed no significant effect of childhood BMI on OM (OR, 1.16; 95% CI, 0.84, 1.62; P = .370), no significant effect of adulthood BMI on OM (OR, 0.42; 95% CI, 0.21, 0.84; P = .015), a significant association between waist circumference and OM (OR, 4.30; 95% CI, 1.89, 9.82; P = .001), T2D mediated 10% (95% CI, 0.02, 0.14), and no significant association between hip circumference and OM (OR, 1.01; 95% CI, 0.54, 1.90; P = .968). Our study provides evidence for a genetically predicted causal relationship among obesity, T2D, and OM. We demonstrate that increased waist circumference is positively associated with an increased risk of OM and that T2D mediates this relationship. Clinicians should be more cautious in the perioperative management of osteomyelitis surgery in obese patients with T2D. In addition, waist circumference may be a more important criterion to emphasize and strictly control than other measures of obesity.

Direct metagenomics investigation of non-surgical hard-to-heal wounds: a review

BACKGROUND

Non-surgical chronic wounds, including diabetes-related foot diseases (DRFD), pressure injuries (PIs) and venous leg ulcers (VLU), are common hard-to-heal wounds. Wound evolution partly depends on microbial colonisation or infection, which is often confused by clinicians, thereby hampering proper management. Current routine microbiology investigation of these wounds is based on in vitro culture, focusing only on a limited panel of the most frequently isolated bacteria, leaving a large part of the wound microbiome undocumented.

METHODS

A literature search was conducted on original studies published through October 2022 reporting metagenomic next generation sequencing (mNGS) of chronic wound samples. Studies were eligible for inclusion if they applied 16 S rRNA metagenomics or shotgun metagenomics for microbiome analysis or diagnosis. Case reports, prospective, or retrospective studies were included. However, review articles, animal studies, in vitro model optimisation, benchmarking, treatment optimisation studies, and non-clinical studies were excluded. Articles were identified in PubMed, Google Scholar, Web of Science, Microsoft Academic, Crossref and Semantic Scholar databases.

RESULTS

Of the 3,202 articles found in the initial search, 2,336 articles were removed after deduplication and 834 articles following title and abstract screening. A further 14 were removed after full text reading, with 18 articles finally included. Data were provided for 3,628 patients, including 1,535 DRFDs, 956 VLUs, and 791 PIs, with 164 microbial genera and 116 species identified using mNGS approaches. A high microbial diversity was observed depending on the geographical location and wound evolution. Clinically infected wounds were the most diverse, possibly due to a widespread colonisation by pathogenic bacteria from body and environmental microbiota. mNGS data identified the presence of virus (EBV) and fungi (Candida and Aspergillus species), as well as Staphylococcus and Pseudomonas bacteriophages.

CONCLUSION

This study highlighted the benefit of mNGS for time-effective pathogen genome detection. Despite the majority of the included studies investigating only 16 S rDNA, ignoring a part of viral, fungal and parasite colonisation, mNGS detected a large number of bacteria through the included studies. Such technology could be implemented in routine microbiology for hard-to-heal wound microbiota investigation and post-treatment wound colonisation surveillance.

Diabetic Foot Infections in the Emergency Department

Diabetic foot infection (DFI) is among the most common diabetic complications requiring hospitalization. Prompt emergency department diagnosis and evidence-based management can prevent eventual amputation and associated disability and mortality. Underlying neuropathy, arterial occlusion, immune dysfunction, and hyperglycemia-associated dehydration and ketoacidosis can all contribute to severity and conspire to make DFI diagnosis and management difficult. Serious complications include osteomyelitis, necrotizing infection, and sepsis. Practice guidelines are designed to assist frontline providers with correct diagnosis, categorization, and treatment decisions. Management generally includes a careful lower extremity examination and plain x-ray, obtaining appropriate tissue cultures, and evidence-based antibiotic selection tailored to severity.

IWGDF/IDSA guidelines on the diagnosis and treatment of diabetes-related foot infections (IWGDF/IDSA 2023)

The International Working Group on the Diabetic Foot (IWGDF) has published evidence-based guidelines on the management and prevention of diabetes-related foot diseases since 1999. The present guideline is an update of the 2019 IWGDF guideline on the diagnosis and management of foot infections in persons with diabetes mellitus. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework was used for the development of this guideline. This was structured around identifying clinically relevant questions in the P(A)ICO format, determining patient-important outcomes, systematically reviewing the evidence, assessing the certainty of the evidence, and finally moving from evidence to the recommendation. This guideline was developed for healthcare professionals involved in diabetes-related foot care to inform clinical care around patient-important outcomes. Two systematic reviews from 2019 were updated to inform this guideline, and a total of 149 studies (62 new) meeting inclusion criteria were identified from the updated search and incorporated in this guideline. Updated recommendations are derived from these systematic reviews, and best practice statements made where evidence was not available. Evidence was weighed in light of benefits and harms to arrive at a recommendation. The certainty of the evidence for some recommendations was modified in this update with a more refined application of the GRADE framework centred around patient important outcomes. This is highlighted in the rationale section of this update. A note is also made where the newly identified evidence did not alter the strength or certainty of evidence for previous recommendations. The recommendations presented here continue to cover various aspects of diagnosing soft tissue and bone infections, including the classification scheme for diagnosing infection and its severity. Guidance on how to collect microbiological samples, and how to process them to identify causative pathogens, is also outlined. Finally, we present the approach to treating foot infections in persons with diabetes, including selecting appropriate empiric and definitive antimicrobial therapy for soft tissue and bone infections; when and how to approach surgical treatment; and which adjunctive treatments may or may not affect the infectious outcomes of diabetes-related foot problems. We believe that following these recommendations will help healthcare professionals provide better care for persons with diabetes and foot infections, prevent the number of foot and limb amputations, and reduce the patient and healthcare burden of diabetes-related foot disease.

Studying Microbial Ecology of Diabetic Foot Infections: Significance of PCR Analysis for Prudent Antimicrobial Stewardship

This study presents a comprehensive investigation into the microbial ecology of diabetic foot infections (DFIs), using molecular-polymerase chain reaction (PCR) analysis to accurately identify the causative agents. One hundred DFI patients were recruited and classified using the Depth Extent Phase and Associated Etiology (DEPA) score according to their severity. Results revealed polymicrobial infections in 75% of cases, predominantly featuring Staphylococcus epidermidis (83%) and Staphylococcus aureus (63%). Importantly, 20% of samples exhibited facultative anaerobes Bacteroides fragilis or Clostridium perfringens, exclusively in high DEPA score ulcers. Candida albicans coinfection was identified in 19.2% of cases, underscoring the need for mycological evaluation. Empirical antimicrobial therapy regimens were tailored to DEPA severity, yet our findings highlighted a potential gap in methicillin-resistant Staphylococcus aureus (MRSA) coverage. Despite an 88% prevalence of methicillin-resistant Staphylococci, vancomycin usage was suboptimal. This raises concerns about the underestimation of MRSA risk and the need for tailored antibiotic guidelines. Our study demonstrates the efficacy of molecular-PCR analysis in identifying diverse microbial communities in DFIs, influencing targeted antibiotic choices. The results advocate for refined antimicrobial guidelines, considering regional variations in microbial patterns and judiciously addressing multidrug-resistant strains. This research contributes crucial insights for optimizing DFIs management and helps the physicians to have a fast decision in selection the suitable antibiotic for each patient and to decrease the risk of bacterial resistance from the improper use of broad-spectrum empirical therapies.

Investigation and management of diabetic foot osteomyelitis: An update for the foot and ankle orthopaedic surgeon

Diabetic foot osteomyelitis (DFO) poses a significant challenge in the management of diabetic patients, often leading to severe complications and increased morbidity. Effective management of DFO requires a multidisciplinary approach, involving endocrinologists, infectious disease specialists, vascular surgeons, orthopaedic surgeons, and wound care experts. Early diagnosis is paramount, facilitated by advanced imaging techniques such as magnetic resonance imaging (MRI) and bone scintigraphy. Once diagnosed, the treatment strategy hinges on a combination of medical and surgical interventions. Antibiotic therapy, guided by culture results, plays a central role in managing DFO. Tailored regimens targeting the specific pathogens involved are administered, often for prolonged durations. Surgical intervention becomes necessary when conservative measures fall short. Surgical approaches range from minimally invasive procedures, like percutaneous drainage, to more extensive interventions like debridement and bone resection. Prevention of DFO recurrence is equally vital, emphasising glycemic control, meticulous foot care, patient education, monitoring of at-risk signs, revascularization and early intervention when indicated. The management of diabetic foot osteomyelitis mandates a comprehensive strategy that addresses both the infectious and surgical aspects of the condition. A collaborative, interdisciplinary approach ensures timely diagnosis, tailored treatment, and holistic care. Further research into novel therapeutic modalities and long-term outcomes remains essential in refining the management of this complex and debilitating complication of diabetes.

The Human Microbiome and Its Role in Musculoskeletal Disorders

Musculoskeletal diseases (MSDs) are characterized as injuries and illnesses that affect the musculoskeletal system. MSDs affect every population worldwide and are associated with substantial global burden. Variations in the makeup of the gut microbiota may be related to chronic MSDs. There is growing interest in exploring potential connections between chronic MSDs and variations in the composition of gut microbiota. The human microbiota is a complex community consisting of viruses, archaea, bacteria, and eukaryotes, both inside and outside of the human body. These microorganisms play crucial roles in influencing human physiology, impacting metabolic and immunological systems in health and disease. Different body areas host specific types of microorganisms, with facultative anaerobes dominating the gastrointestinal tract (able to thrive with or without oxygen), while strict aerobes prevail in the nasal cavity, respiratory tract, and skin surfaces (requiring oxygen for development). Together with the immune system, these bacteria have coevolved throughout time, forming complex biological relationships. Changes in the microbial ecology of the gut may have a big impact on health and can help illnesses develop. These changes are frequently impacted by lifestyle choices and underlying medical disorders. The potential for safety, expenses, and efficacy of microbiota-based medicines, even with occasional delivery, has attracted interest. They are, therefore, a desirable candidate for treating MSDs that are chronic and that may have variable progression patterns. As such, the following is a narrative review to address the role of the human microbiome as it relates to MSDs.

Bacterial biofilms in the human body: prevalence and impacts on health and disease

Bacterial biofilms can be found in most environments on our planet, and the human body is no exception. Consisting of microbial cells encased in a matrix of extracellular polymers, biofilms enable bacteria to sequester themselves in favorable niches, while also increasing their ability to resist numerous stresses and survive under hostile circumstances. In recent decades, biofilms have increasingly been recognized as a major contributor to the pathogenesis of chronic infections. However, biofilms also occur in or on certain tissues in healthy individuals, and their constituent species are not restricted to canonical pathogens. In this review, we discuss the evidence for where, when, and what types of biofilms occur in the human body, as well as the diverse ways in which they can impact host health under homeostatic and dysbiotic states.

Concordance between culture, Molecular Culture and Illumina 16S rRNA gene amplicon sequencing of bone and ulcer bed biopsies in people with diabetic foot osteomyelitis

BACKGROUND

In clinical practice the diagnosis of diabetic foot osteomyelitis (DFO) relies on cultures of bone or ulcer bed (UB) biopsies, of which bone biopsy is reference standard. The slow growth or fastidious nature of some bacteria, hamper expeditious detection and identification. Rapid molecular techniques may solve both issues, but their additional value for everyday practice is unknown. We investigated the concordance between conventional culture, the molecular techniques Molecular Culture (MC), and illumina 16S rRNA gene amplicon (16S) sequencing in people with DFO.

METHODS

In the BeBoP trial, bone and UB biopsies were obtained from people with DFO who visited Amsterdam UMC. These biopsies were analysed using 1) conventional culture, 2)MC, a rapid broad range PCR analysing the 16S-23S ribosomal-interspace-region, and 3) 16S sequencing, and evaluated concordance among these techniques.

RESULTS

We analysed 20 samples (11 bone and 9 UB) of 18 people. A total of 84 infectious agents were identified, 45 (54%) by all techniques, an additional 22 (26.5%, overall 80.5%) by both MC and 16S, and the remaining 16 species by culture and MC or 16S, or by a single method only. MC and 16S identified anaerobes not detected by culturing in 5 samples, and the presence of bacteria in 7 of 8 culture-negative (6 bone, 2 UB) samples.

CONCLUSION

The high level of concordance between MC and 16S and the additional ability of molecular techniques to detect various bacteria not detected by culturing opens up prospects for routine use of fast molecular techniques, in clinical settings including DFO.

TRIAL REGISTRATION

The BeBoP trial is retrospectively registered on 05-03-2019 in Netherlands Trial Register: NL 7582.

Do Anti-Biofilm Antibiotics Have a Place in the Treatment of Diabetic Foot Osteomyelitis?

The choice of antibiotic regimens for use in patients presenting with diabetic foot osteomyelitis and their duration differs according to the situation. Antibiotics play a more important role in the medical option where no infected bone has been resected, while their role is reduced but not negligible in the case of surgical options. Some studies have reported the presence of biofilm structures in bone samples taken from patients with diabetic foot osteomyelitis, which raises the question of the place of anti-biofilm antibiotic regimens in this setting. During the last two decades, clinical studies have suggested a potential benefit for anti-biofilm antibiotics, mainly rifampicin against staphylococci and fluoroquinolones against gram-negative bacilli. However, no data from randomized controlled studies have been reported so far. The present work provides a summary of the available data on the question of the place of anti-biofilm antibiotics for the treatment of diabetic foot osteomyelitis, but also the potential limitations of such treatments.

Bacterial Diversity and Antibiotic Resistance in Patients with Diabetic Foot Osteomyelitis

This study analysed the bacterial diversity, antibiotic susceptibility, and resistance in patients with complications of diabetic foot osteomyelitis (DFO). A retrospective observational study was carried out between September 2019 and September 2022 and involved 215 outpatients with a diagnosis of DFO at a specialized diabetic foot unit. A total of 204 positive bone cultures were isolated, including 62.7% monomicrobial cultures, and 37.3% were formed with at least two microorganisms. We observed that Proteus spp., Coagulase-negative staphylococci (CoNS), Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Corynebacterium were the most frequently isolated microorganisms and accounted for more than 10% of the DFO cases. With stratification by Gram-positive (GP) and Gram-negative (GN) bacteria, we observed that 91.6% of cultures presented at least one GP bacteria species, and 50.4% presented at least one GN bacteria species. The most common GP species were CoNS (29%), S. aureus (25.8%), and Corynebacterium spp. (14%). The most frequent GN species consisted of Proteus spp. (32%), P. aeruginosa (23.3%), and E. coli (17.5%). The main antibiotics with resistance to GP-dominated infections were penicillins without β-lactamase inhibitor, and those in GN-dominated infections were sulfonamides and penicillins without β-lactamase. Significant differences were not observed in mean healing time in DFU with acute osteomyelitis (12.76 weeks (4.50;18)) compared to chronic osteomyelitis (15.31 weeks (7;18.25); p = 0.101) and when comparing cases with soft tissue infection (15.95 (6;20)) and those without such an infection (16.59 (7.25;19.75), p = 0.618). This study shows that when treatment of DFO is based on early surgical treatment, the type of DFO and the presence of soft infection are not associated with different or worse prognoses.

A Comparison of Pathogens in Skin and Soft-Tissue Infections and Pedal Osteomyelitis in Puncture Wound Injuries Affecting the Foot

BACKGROUND

To compare pathogens involved in skin and soft-tissue infections (SSTIs) and pedal osteomyelitis (OM) in patients with and without diabetes with puncture wounds to the foot.

METHODS

We evaluated 113 consecutive patients between June 1, 2011, and March 31, 2019, with foot infection (SSTIs and OM) from a puncture injury sustained to the foot. Eighty-three patients had diabetes and 30 did not. We evaluated the bacterial pathogens in patients with SSTIs and pedal OM.

RESULTS

Polymicrobial infections were more common in patients with diabetes mellitus (83.1% versus 53.3%; P = .001). The most common pathogen for SSTIs and OM in patients with diabetes was Staphylococcus aureus (SSTIs, 50.7%; OM, 32.3%), whereas in patients without diabetes it was Pseudomonas (25%) for SSTIs. Anaerobes (9.4%) and fungal infection (3.1%) were uncommon. Pseudomonas aeruginosa was identified in only 5.8% of people with diabetes.

CONCLUSIONS

The most common bacterial pathogen in both SSTIs and pedal OM was S aureus in patients with diabetes. Pseudomonas species was the most common pathogen in people without diabetes with SSTIs.

Microbiology of diabetic foot osteomyelitis - Is it geographically variable?

INTRODUCTION

Diabetic foot osteomyelitis (DFO) is a dreaded complication as both diagnosis and treatment of the condition is laborious. However, for proper decision on antibiotics in medical management of DFO, accurate determination of microbes is necessary to narrow the spectrum of coverage and to reduce adverse effects of long-term administration of antibiotics. With differing pattern of use of antimicrobials and their resistance pattern in different countries, it is empirical to determine the microbiological characteristics of bone cultures in DFO from a referral institute in South India.

MATERIALS AND METHODS

This study was a retrospective chart review of all cases of proven DFO who had consented for debridement and bone culture or those who underwent amputation. Both deep soft tissue (DST) and bone cultures were obtained for aerobic bacteria. Clinical characteristics and site(s) of DFO were recorded. Investigations for peripheral artery disease were performed if clinically indicated.

RESULTS

In all, 105 patients with DFO were reviewed. Mean age was 62 years and 70% were men. Of those who were screened, 57% had evidence of peripheral arterial disease by arterial doppler. 46% of bone culture samples were sterile. Gram- negative organisms were more common (58%). Following staphylococcus, pseudomonas was the second common isolate. Of total staphylococcal isolates 37% were MRSA and 33% of klebsiella isolates were ESBL producing. Concordance rate between DST and bone cultures was 66%. 90% were mono-bacterial isolates. The commonest site of involvement of DFO was terminal phalanges of toes rather than base of 1st metatarsal.

CONCLUSION

Widespread use of antibiotics, tropical climate and route of entry of organisms causing DFO differed in our cohort of patients. Further studies from different regions of world would shed light onto different pattern of microbes causing DFO.

Microbial Interplay in Skin and Chronic Wounds

Purpose of Review

Microbial infections in chronic wounds can often lead to lower-limb amputation, decrease in quality of life, and increase in mortality rate, and there is an unmet need to distinguish between pathogens and colonisers in these chronic wounds. Hence, identifying the composition of healthy skin microbiota, microbes associated with chronic wound and healing processes, and microbial interactions and host response in healing wounds vs. non-healing wounds can help us in formulating innovative individual-centric treatment protocols.

Recent Findings

This review highlights various metabolites and biomarkers produced by microbes that have been identified to modulate these interactions, particularly those involved in host–microbe and microbe–microbe communication. Further, considering that many skin commensals demonstrate contextual pathogenicity, we provide insights into promising initiatives in the wound microbiome research.

Summary

The skin microbiome is highly diverse and variable, and considering its importance remains to be a hotspot of medical investigations and research to enable us to prevent and treat skin disorders and chronic wound infections. This is especially relevant now considering that non-healing and chronic wounds are highly prevalent, generally affecting lower extremities as seen in diabetic foot ulcers, venous leg ulcers, and pressure ulcers. Pathogenic bacteria are purported to have a key role in deferring healing of wounds. However, the role of skin microflora in wound progression has been a subject of debate. In this review, we discuss biomarkers associated with chronic wound microenvironment along with the relevance of skin microflora and their metabolites in determining the chronicity of wounds.

Metatranscriptome sequencing identifies Escherichia are major contributors to pathogenic functions and biofilm formation in diabetes related foot osteomyelitis

Osteomyelitis in the feet of persons with diabetes is clinically challenging and is associated with high rates of amputation. In this study RNA-sequencing was employed to explore microbial metatranscriptomes with a view to understand the relative activity and functions of the pathogen/s responsible for diabetes foot osteomyelitis (DFO). We obtained 25 intraoperative bone specimens from persons with confirmed DFO, observing that Escherichia spp. (7%), Streptomyces spp. (7%), Staphylococcus spp. (6%), Klebsiella spp. (5%) and Proteus spp. (5%) are the most active taxa on average. Data was then subset to examine functions associated with pathogenesis (virulence and toxins), biofilm formation and antimicrobial/multi-drug resistance. Analysis revealed Escherichia spp. are the most active taxa relative to pathogenic functions with K06218 (mRNA interferase relE), K03699 (membrane damaging toxin tlyC) and K03980 (putative peptidoglycan lipid II flippase murJ), K01114 (membrane damaging toxin plc) and K19168 (toxin cptA) being the most prevalent pathogenic associated transcripts. The most abundant transcripts associated with biofilm pathways included components of the biofilm EPS matrix including glycogen synthesis, cellulose synthesis, colonic acid synthesis and flagella synthesis. We further observed enrichment of a key enzyme involved in the biosynthesis of L-rhamnose (K01710 -dTDP-glucose 4,6-dehydratase rfbB, rmlB, rffG) which was present in all but four patients with DFO.

Conservative surgical treatment for metatarsal osteomyelitis in diabetic foot: experience of two French centres

AIMS

Conservative surgery (CS) for diabetic foot osteomyelitis (DFO) consists in removing all or part of the infected bone tissues without amputation, in complement with antibiotic therapy. Data on CS for DFO therapy are scarce.

MATERIAL AND METHODS

We performed a retrospective analysis of all DFO episodes treated with CS between 06/2007 and 12/2017. Remission was defined by the absence of soft-tissue infection, complete sustained (i.e. > 1 month) healing of the foot ulcer, favourable (i.e., stabilisation or improvement) radiological outcome, and no need for additional surgery during a 1-year follow-up.

RESULTS

During the study period, 47 episodes (in 41 patients) were analysed. Excluding deaths (all unrelated to the DFO; n = 3) or loss to follow-up before 1 year (n = 5), the remission rate was 64.2%. Most failures occurred during the first 6 months (79%, 11/14). Patients who experienced failure had a higher rate of peripheral arterial disease with arterial stenosis than patients in remission (57% vs. 24%, P = 0.03), a higher C-reactive protein rate at admission (116 ± 112 mg/L vs. 48 ± 46 mg/L, P = 0.02), and a trend for a higher rate of abscesses (29% vs. 4%, P = 0.06). At 1-year follow-up, foot ulcers related to transfer lesion were identified in 25.5% of the cases. At the last follow-up (mean 3 ± 2 years), the remission rate was 23/25 (92%).

CONCLUSIONS

Our results suggest that CS is a therapeutic option in patients with localised but severe DFO. Clinicians should, however, consider the necessity of revascularisation, and higher risk of failure if surgery is performed in patients presenting with acute foot infections.

In vitro efficacy of antibiotic loaded calcium sulfate beads (Stimulan Rapid Cure) against polymicrobial communities and individual bacterial strains derived from diabetic foot infections

Introduction. Diabetic foot infection (DFI) is the main reason for diabetes-related hospitalisation and is a major cause of diabetes-related amputation. DFIs are often complicated by ischaemia in the affected limb, the presence of polymicrobial biofilms and increasingly the occurrence of antibiotic resistant bacteria.Hypothesis/Gap statement. Antibiotic loaded beads could inhibit the growth of polymicrobial DFI communities with differing compositions in vitro.Aim. This study investigates the in vitro efficacy of antibiotic loaded calcium sulfate beads (Stimulan Rapid Cure, Biocomposites Ltd., UK) against polymicrobial DFI communities and individual bacterial strains derived from DFIs.Methodology. Debrided tissue obtained from the base of infected diabetic foot ulcers was homogenised and spread over the surface of Columbia blood agar (CBA) and fastidious anaerobe agar (FAA) plates. Calcium sulfate beads containing a combination of vancomycin and gentamicin were then placed on the surface of the agar and following incubation, zones of inhibition (ZOI) were measured. For individual bacterial strains isolated from the infected tissue, calcium sulfate beads containing vancomycin, gentamicin, flucloxacillin or rifampicin and beads containing a combination of vancomycin and gentamicin or flucloxacillin and rifampicin were tested for their ability to inhibit growth.Results. Calcium sulfate beads loaded with a combination of vancomycin and gentamicin were able to inhibit bacterial growth from all polymicrobial tissue homogenates tested, with ZOI diameters ranging from 15 to 40 mm. In the case of individual bacterial strains, beads containing combinations of vancomycin and gentamicin or flucloxacillin and rifampicin were able to produce ZOI with Gram-positive facultatitive anaerobic strains such as Staphylococcus aureus and Enterococcus faecalis, Gram-negative facultative anaerobic strains such as Pseudomonas aeruginosa and obligate anaerobic strains such as Finegoldia magna even where acquired resistance to one of the antibiotics in the combination was evidenced.Conclusion. The local use of calcium sulfate beads containing a combination of two antibiotics demonstrated high efficacy against polymicrobial DFI communities and individual DFI bacterial strains in in vitro zone of inhibition tests. These results show promise for clinical application, but further research and clinical studies are required.

Biofilm Survival Strategies in Chronic Wounds

Bacterial biofilms residing in chronic wounds are thought to have numerous survival strategies, making them extremely difficult to eradicate and resulting in long-term infections. However, much of our knowledge regarding biofilm persistence stems from in vitro models and experiments performed in vivo in animal models. While the knowledge obtained from such experiments is highly valuable, its direct translation to the human clinical setting should be undertaken with caution. In this review, we highlight knowledge obtained from human clinical samples in different aspects of biofilm survival strategies. These strategies have been divided into segments of the following attributes: altered transcriptomic profiles, spatial distribution, the production of extracellular polymeric substances, an altered microenvironment, inter-and intra-species interactions, and heterogeneity in the bacterial population. While all these attributes are speculated to contribute to the enhanced persistence of biofilms in chronic wounds, only some of them have been demonstrated to exist in human wounds. Some of the attributes have been observed in other clinical diseases while others have only been observed in vitro. Here, we have strived to clarify the limitations of the current knowledge in regard to this specific topic, without ignoring important in vitro and in vivo observations.

Emerging Diabetic Foot Ulcer Microbiome Analysis Using Cutting Edge Technologies

One of the most prevalent complications of diabetes mellitus are diabetic foot ulcers (DFU). Diabetic foot ulcers represent a complex condition placing individuals at-risk for major lower extremity amputations and are an independent predictor of patient mortality. DFU heal poorly when standard of care therapy is applied. In fact, wound healing occurs only approximately 30% within 12 weeks and only 45% regardless of time when standard of care is utilized. Similarly, diabetic foot infections occur in half of all DFU and conventional microbiologic cultures can take several days to process before a result is known. DFU represent a significant challenge in this regard because DFU often demonstrate polymicrobial growth, become resistant to preferred antibiotic therapy, and do not inform providers about long-term prognosis. In addition, conventional culture yields may be affected by the timing of antibiotic administration and collection of tissue for analysis. This may lead to suboptimal antibiotic administration or debilitating amputations. The microbiome of DFU is a new frontier to better understand the interactions between host organisms and pathogenic ones. Newer molecular techniques are readily available to assist in analyzing the constituency of the microbiome of DFU. These emerging techniques have already been used to study the microbiome of DFU and have clinical implications that may alter standard of care practice in the near future. Here emerging molecular techniques that can provide clinicians with rapid DFU-related-information and help prognosticate outcomes in this vulnerable patient population are presented.

Human skin microbiota in health and disease: The cutaneous communities' interplay in equilibrium and dysbiosis: The cutaneous communities' interplay in equilibrium and dysbiosis

Cutaneous microbial composition is driven by the microenvironment of the skin, as well as by internal and external factors. Local changes in the microenvironment can affect the configuration of the community, which may lead toward an imbalance of microbiota. Alterations in the microbial profile are common in both inflammatory skin diseases and chronic infections. A shift in balance within the microbiota, toward limited variation and a greater abundance of specific pathogens, may further worsen the pathogenicity of the diseases. These alterations may be prevented by topical treatment of probiotic solutions stimulating a balanced multispecies community. Compositional variations may further constitute potential biomarkers to predict flares or monitor efficacy during therapy. New approaches such as machine learning may contribute to this prediction of microbial alterations prior to the development of chronic infections and flares. This review provides insight into the composition and distribution of a healthy community of microorganisms in the skin and draws parallels with the community in chronic infections and chronic inflammatory skin diseases such acne vulgaris and Hidradenitis Suppurativa. We discuss the potential role of specific species in the pathogenesis and the possible prevention of disease exacerbation.

Comparative study of culture, next-generation sequencing, and immunoassay for identification of pathogen in diabetic foot ulcer

Treatment of deep musculoskeletal infection (MSKI) begins with accurate identification of the offending pathogen, surgical excision/debridement, and a course of culture-directed antibiotics. Despite this, the incidence of recurrent infection continues to rise. A major contributor to this is inaccurate or negative initial cultures. Accurate identification of the main pathogen is paramount to treatment success. This is especially important in treating diabetic foot infections (DFIs) with limb salvage efforts. This study seeks to utilize standard culture, next-generation sequencing (NGS), and immunoassay for newly synthesized antibodies (NSA) to Staphylococcus aureus and Streptococcus agalactiae for diagnosis. This is a level II prospective observational study approved by our IRB. Thirty patients > 18 years of age who presented with a DFI and underwent surgical debridement or amputation by a single academic orthopedic surgeon from October 2018 to September 2019 were enrolled. Intraoperative samples were obtained from the base of the wound and sent for culture, NGS, and a peripheral blood sample was obtained at the time of diagnosis. NGS and culture were highly correlated for S. aureus (κ = 0.86) and S. agalactiae (κ = 1.0), NSA immunoassay and culture demonstrated a fair correlation for S. aureus (κ = 0.18) and S. agalactiae (κ = 0.67), and NGS and NSA immunoassay demonstrated fair correlation for S. aureus (κ = 0.1667) and S. agalactiae (κ = 0.67). Our study demonstrates a high concordance between culture and NGS in identifying the dominant pathogen in DFU. NGS may be a useful adjunct in DFI diagnosis.

Impact of the Host-Microbiome on Osteomyelitis Pathogenesis

The microbiome is a collection of genomes from microbiota, including all microorganisms in a niche, through direct and indirect interactions with the host. Certain microorganisms can exist in areas conventionally considered to be sterile, such as the bone matrix. Osseous microbiota dysbiosis caused by host-microbiome perturbation or external infections may ultimately lead to osteomyelitis, a bone inflammatory disorder. Our review covers the current discoveries on the impact of host-microbiome on osteomyelitis and some common osseous diseases. Some studies suggest that the microbiotas from both osseous and non-osseous tissues (e.g., blood or gut) impact the pathogenicity of osteomyelitis and other osseous diseases (e.g., rheumatoid arthritis). We believe that this review will provide readers with a better understanding on the role of the microbiome to the host’s bone health.

Next-Generation Sequencing for Pathogen Identification in Infected Foot Ulcers

Background:

Accurate identification of primary pathogens in foot infections remains challenging due to the diverse microbiome. Conventional culture may show false-positive or false-negative growth, leading to ineffective postoperative antibiotic treatment. Next-generation sequencing (NGS) has been explored as an alternative to standard culture in orthopedic infections. NGS is highly sensitive and can detect an entire bacterial genome along with genes conferring antibiotic resistance in a given sample. We investigated the potential use of NGS for accurate identification and quantification of microbes in infected diabetic foot ulcer (DFU). We hypothesize that NGS will aid identification of dominant pathogen and provide a more complete profile of microorganisms in infected DFUs compared to the standard culture method.

Methods:

Data were prospectively collected from 30 infected DFU patients who underwent operative treatment by a fellowship-trained orthopedic foot and ankle surgeon from October 2018 to September 2019. The average age of the patient was 60.4 years. Operative procedures performed were irrigation and debridement (12), toe or ray amputation (13), calcanectomies (4), and below-the-knee amputation (1). Infected bone specimens were obtained intraoperatively and processed for standard culture and NGS. Concordance between the standard culture and NGS was assessed.

Results:

In 29 of 30 patients, pathogens were identified by both NGS and culture, with a concordance rate of 70%. In standard culture, Staphylococcus aureus (58.6%) was the most common pathogen, followed by coagulase-negative Staphylococcus (24.1%), Corynebacterium striatum (17.2%), and Enterococcus faecalis (17.2%). In NGS, Finegoldia magna (44.8%) was the most common microorganism followed by S. aureus (41.4%), and Anaerococcus vaginalis (24.1%). On average, NGS revealed 5.1 (range, 1-11) pathogens in a given sample, whereas culture revealed 2.6 (range, 1-6) pathogens.

Conclusion:

NGS is an emerging molecular diagnostic method of microbial identification in orthopedic infection. It frequently provides different profiles of microorganisms along with antibiotic-resistant gene information compared to conventional culture in polymicrobial foot infection. Clinical use of NGS for management of foot and ankle infections warrants further investigation.

Level of Evidence:

Level II, diagnostic study.

Metagenomics to Identify Pathogens in Diabetic Foot Ulcers and the Potential Impact for Clinical Care

PURPOSE OF REVIEW

Diabetes mellitus may affect every third adult American by 2050, and about one-third will develop a diabetic foot ulcer (DFU) during their lifetime. The current standard of care results in healing of less than 50% of all DFUs. Many individuals with DFU develop limb-threatening infection which place them at risk for additional morbidity and mortality. We review research associated with culture-independent next-generation sequencing techniques pertaining to diabetic foot ulcers and their potential for clinical application.

RECENT FINDINGS

Diabetic foot ulcers are a growing problem and clinicians are limited by their reliance on conventional culture. Metagenomic sequencing technology provides an unparalleled viewpoint of the polymicrobial constituency of DFU. The microbiome techniques used to study the microbial constituency of DFU may offer insight to improve care for these patients, but without standardized approaches in research based on real-world clinical practices, a significant knowledge gap will remain.

Nanopore 16S Amplicon Sequencing Enhances the Understanding of Pathogens in Medically Intractable Diabetic Foot Infections

Diabetic foot infections (DFIs) cause substantial morbidity and mortality. The mainstay of the treatment is empiric antibiotics and surgical debridement in severe cases. In this study, we performed nanopore 16S rDNA sequencing from the debridement specimens of DFIs. Fifty-four surgical debridement specimens obtained from 45 patients with medically intractable DFI were included. The 16S rDNA PCR was performed on each specimen, and Nanopore sequencing was performed for up to 3 h. The reads were aligned to the BLAST database, and the results were compared with conventional culture studies. The 16S sequencing results revealed that the majority of the DFIs (44 of 54, 81.5%) were polymicrobial infections. All bacteria isolated by conventional culture studies were detected by 16S sequencing. Several anaerobes (Prevotella, Finegoldia, Anaerococcus, Bacteroides) were commonly identified by 16S sequencing but were frequently missed by culture studies. In many cases, certain bacteria only revealed by the 16S sequencing were more abundant than the bacteria isolated by the culture studies. In conclusion, nanopore 16S sequencing was capable of pathogen identification in DFIs and has many advantages over conventional culture studies. Nanopore 16S sequencing enables a comprehensive understanding of the bacteria involved in DFIs.

Biofilm-Innate Immune Interface: Contribution to Chronic Wound Formation

Delayed wound healing can cause significant issues for immobile and ageing individuals as well as those living with co-morbid conditions such as diabetes, cardiovascular disease, and cancer. These delays increase a patient’s risk for infection and, in severe cases, can result in the formation of chronic, non-healing ulcers (e.g., diabetic foot ulcers, surgical site infections, pressure ulcers and venous leg ulcers). Chronic wounds are very difficult and expensive to treat and there is an urgent need to develop more effective therapeutics that restore healing processes. Sustained innate immune activation and inflammation are common features observed across most chronic wound types. However, the factors driving this activation remain incompletely understood. Emerging evidence suggests that the composition and structure of the wound microbiome may play a central role in driving this dysregulated activation but the cellular and molecular mechanisms underlying these processes require further investigation. In this review, we will discuss the current literature on: 1) how bacterial populations and biofilms contribute to chronic wound formation, 2) the role of bacteria and biofilms in driving dysfunctional innate immune responses in chronic wounds, and 3) therapeutics currently available (or underdevelopment) that target bacteria-innate immune interactions to improve healing. We will also discuss potential issues in studying the complexity of immune-biofilm interactions in chronic wounds and explore future areas of investigation for the field.

Efficacy of a topical concentrated surfactant gel on microbial communities in non-healing diabetic foot ulcers with chronic biofilm infections: A proof-of-concept study

This proof‐of‐concept study sought to determine the effects of standard of care (SOC) and a topically applied concentrated surfactant gel (SG) on the total microbial load, community composition, and community diversity in non‐healing diabetic foot ulcers (DFUs) with chronic biofilm infections. SOC was provided in addition to a topical concentrated SG, applied every 2 days for 6 weeks. Wound swabs were obtained from the base of ulcers at baseline (week 0), week 1, mid‐point (week 3), and end of treatment (week 6). DNA sequencing and real‐time quantitative polymerase chain reaction (qPCR) were employed to determine the total microbial load, community composition, and diversity of patient samples. Tissue specimens were obtained at baseline and scanning electron microscopy and peptide nucleic acid fluorescent in situ hybridisation with confocal laser scanning microscopy were used to confirm the presence of biofilm in all 10 DFUs with suspected chronic biofilm infections. The application of SG resulted in 7 of 10 samples achieving a reduction in mean log10 total microbial load from baseline to end of treatment (0.8 Log10 16S copies, ±0.6), and 3 of 10 samples demonstrated an increase in mean Log10 total microbial load (0.6 log10 16S copies, ±0.8) from baseline to end of treatment. Composition changes in microbial communities were driven by changes to the most dominant bacteria. Corynebacterium sp. and Streptococcus sp. frequently reduced in relative abundance in patient samples from week 0 to week 6 but did not disappear. In contrast, Staphylococcus sp., Finegoldia sp., and Fusobacterium sp., relative abundances frequently increased in patient samples from week 0 to week 6. The application of a concentrated SG resulted in varying shifts to diversity (increase or decrease) between week 0 and week 6 samples at the individual patient level. Any shifts in community diversity were independent to changes in the total microbial loads. SOC and a topical concentrated SG directly affect the microbial loads and community composition of DFUs with chronic biofilm infections.

Distant metastatic foci of infection in adult patients with diabetic foot - not as rare as we think?: case series and review of the literature

BACKGROUND

Diabetic foot is one of the common complications of diabetes mellitus. We report clinical and microbiological characteristics and outcomes of cases with distant metastatic foci of infection arising from diabetic foot.

METHODS

Retrospective review of adult patients with diabetic foot infection or diabetic foot ulcer who demonstrated distant metastatic foci of infection between August 2017 and December 2019. We performed a literature search of similar cases published until June 2020.

RESULTS

Twelve patients with diabetic foot infection or diabetic foot ulcer with distant metastatic foci of infection were identified. The median age of patients was 67.5 years (range 60.5-73.5 years) and 11 males. The most common distant metastatic foci of infection included endocarditis (n = 7) followed by septic arthritis (n = 3) and spine infections (n = 2). Five patients had multiple site and organ involvement. Staphylococcus aureus was the only organism isolated from blood (n = 11), diabetic foot (n = 7), and metastatic foci (n = 8) sources. Three patients died and three had a relapse of distant metastatic foci of infection. Thirty-eight cases were identified in the literature with similar characteristics.

CONCLUSIONS

Prevalence of distant metastatic foci of infection in adult patients with diabetic foot and burden of illness, in terms of mortality, morbidity, and length of hospital stay, appears to be underreported in the literature. A large prospective study is needed to assess the true prevalence of complications, associated risk factors, outcomes and prognostic factors.

Diabetic foot infection and osteomyelitis. Are deep-tissue cultures necessary?

Introduction

Diabetic foot infections (DFIs) are common and difficult to treat. The objective of this study was to compare swab and tissue cultures as indicators of appropriate treatment of DFIs.

Methods

This is a prospective study conducted during a 4-year period. All patients with DFIs and/or diabetic foot osteomyelitis (DFO) admitted to the University Hospital of Heraklion, Greece, were included. Clinical data were collected, while cultures taken with swabs and/or tissue biopsies were used as indicators of the microbiological cause and the appropriate treatment.

Results

In total, 83 individuals (62.7% males) with mean age of 72 years, were enrolled. Coexisting osteomyelitis was present in 18.1%. From tissue and pus cultures, 131 and 176 pathogens, respectively, were isolated. Gram-positive aerobes were the most common microorganisms, followed by Gram-negatives. Infection was polymicrobial in 40 (70.2%) out of 57 patients with tissue culture and in 54 (75.0%) out of 72 with pus culture. Microbiological results from tissue cultures were compatible with those from pus at a rate of 80%, while in cases of osteomyelitis concordance reached 100%. Multidrug-resistant organisms (MDROs) were isolated from 32 (24.4%) tissue and 44 (25%) pus cultures (p=0.910). Initial empirical antimicrobial treatment was considered inappropriate in 44.6% of cases.

Conclusions

A high concordance between easily taken swab cultures and those taken by biopsy was noted, especially in DFO. This was helpful for early change to appropriate treatment in cases where MDROs were isolated and empirical treatment was inappropriate. Further research is needed to confirm this observation in clinical practice.

Skin and Soft Tissue Infections in Patients with Diabetes Mellitus

Skin and soft tissue infections are common in diabetics. Diabetic foot infection usually results from disruption of the skin barrier, trauma, pressure, or ischemic wounds. These wounds may become secondarily infected or lead to development of adjacent soft tissue or deeper bone infection. Clinical assessment and diagnosis of these conditions using a multidisciplinary management approach, including careful attention to antibiotic selection, lead to the best outcomes in patient care.

Do Mixed-Species Biofilms Dominate in Chronic Infections?-Need for in situ Visualization of Bacterial Organization

Chronic infections present a serious economic burden to health-care systems. The severity and prevalence of chronic infections are continuously increasing due to an aging population and an elevated number of lifestyle related diseases such as diabetes. Treatment of chronic infections has proven difficult, mainly due to the presence of biofilms that render bacteria more tolerant toward antimicrobials and the host immune response. Chronic infections have been described to harbor several different bacterial species and it has been hypothesized that microscale interactions and mixed-species consortia are present as described for most natural occurring biofilms i.e., aquatic systems and industrial settings, but also for some commensal human biofilms i.e., the mouth microbiota. However, the presence of mixed-species biofilms in chronic infections is most often an assumption based on culture-based methods and/or by means of molecular approaches, such as PCR and sequencing performed from homogenized bulk tissue samples. These methods disregard the spatial organization of the bacterial community and thus valuable information on biofilm aggregate composition, spatial organization, and possible interactions between different species is lost. Hitherto, only few studies have made visual in situ presentations of mixed-species biofilms in chronic infections, which is pivotal for the description of bacterial composition, spatial distribution, and interspecies interaction on the microscale. In order for bacteria to interact (synergism, commensalism, mutualism, competition, etc.) they need to be in close proximity to each other on the scale where they can affect e.g., solute concentrations. We argue that visual proof of mixed species biofilms in chronic infections is scarce compared to what is seen in e.g., environmental biofilms and call for a debate on the importance of mixed-species biofilm in chronic infections.

Surgical techniques for Bone Biopsy in Diabetic Foot Infection, and association between results and treatment duration

Surgery is an important part of the management of patients diagnosed with DFO. It consists in some selected patients, to remove all or part of the infected bone(s) or even to amputate all or part of the foot. Despite the use of sophisticated imaging techniques, it is however difficult to remove all the infected tissue while respecting the principles of an economical surgery. Bone biopsy performed at the margins of the resection permits to identify residual osteomyelitis and to adjust the post-surgical antibiotic treatment. Some recent studies have reported the way to perform bone margin biopsies and have assessed the impact of the bone results on the patient's outcome. However, the real impact of a residual osteomyelitis on the risk of recurrent DFO is still debated and questions regarding the interpretation of the results remain to be solved. Similarly, the consequences in terms of choice and duration of the antimicrobial treatment to use in case of positive bone margin are not clearly established.

Admission Time Deep Swab Specimens Compared With Surgical Bone Sampling in Hospitalized Individuals With Diabetic Foot Osteomyelitis and Soft Tissue Infection

Whether deep swab cultures taken at admission reliably identify pathogens compared to surgical bone specimens in hospitalized individuals with diabetic foot osteomyelitis and soft tissue infection is unclear. Comparison of microbiological isolates between a deep wound swab (DWS) taken at the time of admission through the actively infected, discharging ulcer probing to the bone and the subsequent surgical bone sample (SBS) taken during surgical debridement was made. A total of 63 subjects (age 60.8 ± 13.5 years, 75% male, 80% Type 2 diabetes, HbA1C 8.9%±2.2%) were included. The proportion of Gram-positive (DWS 49% v SBS 52%) and Gram-negative (DWS 60% v SBS 60%) isolates was similar between the techniques. However, the overall concordance of isolates between the two techniques was only fair (κ=0.302). The best concordance was observed for Staphylococcus aureus (κ=0.571) and MRSA (κ=0.644). There was a correlation between number of isolates in SBS with prior antibiotic therapy of any duration (r= -0.358, p=0.005) and with the duration of ulceration (r=0.296, p=0.045); no clinical correlations were found for DWS. Prior antibiotic therapy (p=0.03) and duration of ulceration <8 weeks (p=0.025) were predictive of negative growth on SBS. In conclusion, we found only a fair concordance between deep wound swabs acquired at admission and surgical bone specimens in those presenting with a severe diabetic foot infection and features of osteomyelitis. Ensuring early surgical debridement of all infected tissue and obtaining bone specimens should be considered a clinical priority, which may also reduce the likelihood of negative growth on SBS.

Diagnosing diabetic foot osteomyelitis

Bone involvement during an infection of the diabetic foot represents a serious complication associated with a high risk of amputation, prolonged antibiotic treatment and hospitalization. Diabetic foot osteomyelitis (DFOs) require a multidisciplinary approach given the usual complexity of these situations. DFO should be suspected in most cases especially in the most severe forms of soft tissue diabetic foot infections (DFIs) where the prevalence of bone infection may be up to 60%. Suspicion is based on clinical signs in particular a positive probe-to-bone (PTB) test, elevated inflammatory biomarkers especially erythrocyte sedimentation rate and abnormal imaging assessment using plain X-ray as a first-line choice. The combination of PTB test with plain X-ray has proven effective in the diagnosis of DFO. The confirmation (definite) diagnosis of DFO is based on the results of a bone sample examination obtained by either surgical or percutaneous biopsy. Sophisticated imaging examinations such as Magnetic Resonance Imaging (MRI) and nuclear imaging techniques are useful where doubt persists after first-line imaging assessment. These techniques may also help localize the bone infection site and increase the diagnostic performance of percutaneous bone biopsy. The quality of the microbiological documentation of DFO is likely to improve the adequacy of the antimicrobial therapy especially when medical (ie, no surgical resection of the infected bone tissues) is considered. The use of new (molecular) techniques for the identification of the bone pathogens have not yet proven superiority on classic cultural techniques for the management of such patients.

Diagnosis of infection in the foot in diabetes: a systematic review

BACKGROUND

Securing an early accurate diagnosis of diabetic foot infections and assessment of their severity are of paramount importance since these infections can cause great morbidity and potentially mortality and present formidable challenges in surgical and antimicrobial treatment.

METHODS

In June 2018, we searched the literature using PuEbMed and EMBASE for published studies on the diagnosis of diabetic foot infection. On the basis of predetermined criteria, we reviewed prospective controlled, as well as noncontrolled, studies in any language, seeking translations for those not in English. We then developed evidence statements on the basis of the included papers.

RESULTS

From the 4242 records screened, we selected 35 papers that met our inclusion criteria. The quality of all but one of the evidence statements was low because of the weak methodology of nearly all of the studies. The available data suggest that diagnosing diabetic foot infections on the basis of clinical signs and symptoms and classified according to the International Working Group of the Diabetic Foot scheme correlates with the patient's likelihood of ulcer healing, of lower extremity amputation, and risk of death. Elevated levels of selected serum inflammatory markers are supportive, but not diagnostic, of soft tissue or bone infection. In patients with suspected diabetic foot osteomyelitis, both a positive probe-to-bone test and an elevated erythrocyte sedimentation rate are strongly associated with its presence. Culturing tissue samples of soft tissues or bone, when care is taken to avoid contamination, provides more accurate microbiological information than culturing superficial (swab) samples. Plain X-ray remains the first-line imaging examination when there is suspicion of diabetic foot osteomyelitis, but advanced imaging methods help in cases when either the diagnosis or the localization of infection is uncertain.

CONCLUSION

The results of this first reported systematic review on the diagnosis of diabetic foot infections provide some guidance for clinicians, but there is a need for more prospective controlled studies of high quality.

Guidelines on the diagnosis and treatment of foot infection in persons with diabetes (IWGDF 2019 update)

The International Working Group on the Diabetic Foot (IWGDF) has published evidence-based guidelines on the prevention and management of diabetic foot disease since 1999. This guideline is on the diagnosis and treatment of foot infection in persons with diabetes and updates the 2015 IWGDF infection guideline. On the basis of patient, intervention, comparison, outcomes (PICOs) developed by the infection committee, in conjunction with internal and external reviewers and consultants, and on systematic reviews the committee conducted on the diagnosis of infection (new) and treatment of infection (updated from 2015), we offer 27 recommendations. These cover various aspects of diagnosing soft tissue and bone infection, including the classification scheme for diagnosing infection and its severity. Of note, we have updated this scheme for the first time since we developed it 15 years ago. We also review the microbiology of diabetic foot infections, including how to collect samples and to process them to identify causative pathogens. Finally, we discuss the approach to treating diabetic foot infections, including selecting appropriate empiric and definitive antimicrobial therapy for soft tissue and for bone infections, when and how to approach surgical treatment, and which adjunctive treatments we think are or are not useful for the infectious aspects of diabetic foot problems. For this version of the guideline, we also updated four tables and one figure from the 2016 guideline. We think that following the principles of diagnosing and treating diabetic foot infections outlined in this guideline can help clinicians to provide better care for these patients.

Management of diabetic foot infections in the light of recent literature and new international guidelines

Introduction: In May 2019 the International Working Group on the Diabetic Foot (IWGDF) launched their quadrennially updated guidelines on the management of diabetic foot infections (DFIs). Concomitantly, the number of new publications regarding DFI increased.Areas covered: The IWGDF committee developed and addressed key questions and produced evidence-based recommendations related to diagnosing and treating DFIs. This narrative review provides an overview of this new guideline and also of other recently published literature in the field of DFIs.Expert opinion: The 2019 IWGDF guidelines provide an authoritative, international, evidence-based approach to diagnosing and treating DFIs. The 27 recommendations are supported by systematic reviews of both diagnosis and interventions. Our review of this guideline, along with other recent publications in the field, allows us to offer state-of-the-art guidance for caring for these difficult infections. As the evidence base for management of DFIs remains suboptimal, we need further research to improve the management of DFIs.

Analysis of proximal bone margins in diabetic foot osteomyelitis by conventional culture, DNA sequencing and microscopy

Multiple approaches were employed to detect pathogens from bone margins associated with Diabetic Foot Osteomyelitis (DFO). Intra-operative bone specimens of 14 consecutive subjects with suspected DFO were collected over a six-month study period from Liverpool Hospital. Infected bone and a proximal bone margins presumed to be 'clean/non-infected' were collected. Bone material was subjected to conventional culture, DNA sequencing and microscopy. In total, eight of 14 (57%) proximal bone margins had no growth by conventional culture but were identified in all proximal bone specimens by DNA sequencing. Proximal margins had lower median total microbial counts than infected specimens, but these differences were not statistically significant. Pathogens identified by sequencing in infected specimens were identified in proximal margins and the microbiomes were similar (ANOSIM = 0.02, p = 0.59). Using a combination of SEM and/or PNA-FISH, we visualized the presence of microorganisms in infected bone specimens and their corresponding proximal margins of seven patients (50%) with DFO. We identify that bacteria can still reside in what seems to be proximal 'clean' margins. The significance and implications of clinical outcomes requires further analysis from a larger sample size that incorporates differences in surgical and post-operative approaches, correlating any outcomes back to culture-sequence findings.

A Clinical Review of Diabetic Foot Infections

"Diabetic foot infections (DFIs) are a common cause of morbidity and mortality. This article summarizes current knowledge regarding DFI epidemiology, disease pathogenesis, and the impact of antimicrobial resistance among DFI. An evidence-based approach to clinical assessment, diagnosing osteomyelitis, as well as medical and surgical treatment is discussed, including a review of empiric and directed antibiotic treatment recommendations. The current state and needs of the clinical literature are identified throughout, with a discussion of the supporting role of infectious diseases specialists as well as future directions of the field."