Prospective Analysis of Surgical Bone Margins After Partial Foot Amputation in Diabetic Patients Admitted With Moderate to Severe Foot Infections

Microbiological characterization of neuropathic diabetic foot infection: a retrospective study at a Portuguese tertiary hospital

Diabetic foot infection imposes a significant burden and is the major cause of nontraumatic limb amputation. Adequate patient management with effective antibiotic therapy is crucial.This retrospective cohort study aimed to characterize the microbiology and resistance patterns of moderate to severe neuropathic diabetic foot infection in patients hospitalized at a tertiary referral hospital between January 2020 and June 2023. Deep tissue specimens from ulcers were collected for culture.Sixty inpatients were included (62% male, mean age 59.1 ± 11.5 years). Osteomyelitis was present in 90% of the patients. Among 102 microorganisms (average of 1.91 ± 1.25 pathogens per patient), 60.8% were gram-positive bacteria, 31.4% were gram-negative, 3.92% were anaerobic bacteria, and 3.92% were fungi. Staphylococcus aureus (19%) and Enterococcus faecium (17%) were the most common. Pseudomonas aeruginosa (8%) and bacteria of the Enterobacterales family (24%) accounted for all the isolated gram-negative bacteria. Sixteen percent of Staphylococcus aureus and 67% of coagulase-negative Staphylococci were resistant to methicillin. Resistance to ampicillin was found in 11% of Enterococci. All Pseudomonas aeruginosa isolates were sensitive to piperacillin-tazobactam, ceftazidime, or cefepime. Among the Enterobacterales, resistance rates were 35% for piperacillin-tazobactam, 38% for ceftazidime, 21% for cefepime, and 13% for carbapenems.Although the prevalence of methicillin-resistant staphylococci was lower than that in other studies, carbapenem resistance among gram-negative bacteria warrants attention. This study highlights the importance of understanding local epidemiology for effective diabetic foot infection management and resistance mitigation.

Diagnosis of infection in the foot of patients with 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 potential mortality and present formidable challenges in surgical and antimicrobial treatment.

METHODS

In June 2022, we searched the literature using PubMed and EMBASE for published studies on the diagnosis of diabetic foot infection (DFI). On the basis of pre-determined criteria, we reviewed prospective controlled, as well as non-controlled, studies in English. We then developed evidence statements based on the included papers.

RESULTS

We selected a total of 64 papers that met our inclusion criteria. The certainty of the majority 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/Infectious Diseases Society of America scheme correlates with the patient's likelihood of the need for hospitalisation, lower extremity amputation, and risk of death. Elevated levels of selected serum inflammatory markers such as erythrocyte sedimentation rate (ESR), C-reactive protein and procalcitonin are supportive, but not diagnostic, of soft tissue infection. 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. Although non-culture techniques, especially next-generation sequencing, are likely to identify more bacteria from tissue samples including bone than standard cultures, no studies have established a significant impact on the management of patients with DFIs. In patients with suspected diabetic foot osteomyelitis, the combination of a positive probe-to-bone test and elevated ESR supports this diagnosis. Plain X-ray remains the first-line imaging examination when there is suspicion of diabetic foot osteomyelitis (DFO), but advanced imaging methods including magnetic resonance imaging (MRI) and nuclear imaging when MRI is not feasible help in cases when either the diagnosis or the localisation of infection is uncertain. Intra-operative or non-per-wound percutaneous biopsy is the best method to accurately identify bone pathogens in case of a suspicion of a DFO. Bedside percutaneous biopsies are effective and safe and are an option to obtain bone culture data when conventional (i.e. surgical or radiological) procedures are not feasible.

CONCLUSIONS

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

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.

Evaluation of routine proximal bone analysis for microbiology and histopathology in diabetes-related foot infections and osteomyelitis

PURPOSE

The value of proximal bone analysis for surgical clearance of infection remains debated. Real-world practice traditionally utilized proximal bone microbiology rather than histopathology to diagnose residual diabetes-related osteomyelitis of the foot (DFO) post-amputation. We assessed the concordance between proximal bone microbiology and histopathology in determining residual infection and their predictability for revision operation in DFO and diabetes-related foot infection (DFI).

METHODOLOGY

A single-centre retrospective study was conducted between June and December 2020 at a tertiary institution. We recruited patients with diabetes mellitus who had minor amputations for DFO and DFI and analyzed their proximal bone microbiology, histopathology and outcomes at 6 months.

RESULTS

Eighty-four patients were recruited; 64 (76.2%) were male. The mean age was 69.3 years. The mean HbA1c was 8.6%. Seventy-seven operations were performed for DFO and 17 for DFI. Negative microbiology showed complete concordance with histopathology; and none had revision operation (P = 0.99). Positive microbiology had 9.8% concordance with histopathology (P = 0.99). Positive histopathology was associated with a higher rate of revision operation (80% vs. 12.5%; P = 0.01). High preoperative C-reactive protein was associated with residual DFO (P = 0.02) and revision operation (P = 0.01).

CONCLUSION

Positive histopathology was more reliable for determining significant residual DFO and predicting revision operation. Positive microbiology was valuable for guiding antibiotic selection. We suggest routine proximal bone analysis for both histopathology and microbiology to optimize the treatment of DFO and DFI.

Clinical practice recommendations for infectious disease management of diabetic foot infection (DFI) - 2023 SPILF

In march 2020, the International Working Group on the Diabetic Foot (IWGDF) published an update of the 2015 guidelines on the diagnosis and management of diabetic foot infection (DFI). While we (the French ID society, SPILF) endorsed some of these recommendations, we wanted to update our own 2006 guidelines and specifically provide informative elements on modalities of microbiological diagnosis and antibiotic treatment (especially first- and second-line regiments, oral switch and duration). The recommendations put forward in the present guidelines are addressed to healthcare professionals managing patients with DFI and more specifically focused on infectious disease management of this type of infection, which clearly needs a multidisciplinary approach. Staging of the severity of the infection is mandatory using the classification drawn up by the IWGDF. Microbiological samples should be taken only in the event of clinical signs suggesting infection in accordance with a strict preliminarily established protocol. Empirical antibiotic therapy should be chosen according to the IWGDF grade of infection and duration of the wound, but must always cover methicillin-sensitive Staphylococcus aureus. Early reevaluation of the patient is a fundamental step, and duration of antibiotic therapy can be shortened in many situations. When osteomyelitis is suspected, standard foot radiograph is the first-line imagery examination and a bone biopsy should be performed for microbiological documentation. Histological analysis of the bone sample is no longer recommended. High dosages of antibiotics are recommended in cases of confirmed osteomyelitis.

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.

Empirical Antibiotic Therapy in Diabetic Foot Ulcer Infection Increases Hospitalization

Background

We evaluated the outcomes associated with initial antibiotic management strategies for infected diabetic foot ulcers (DFUs) diagnosed in an outpatient multidisciplinary center.

Methods

Consecutive outpatient individuals with infected DFUs, stratified according to Infectious Diseases Society of America infection severity, were followed for 1 year from the initial antibiotic administration to treat acute infection. The main outcomes were hospitalization rates for a diabetes-related foot complication within 30 days of diagnosis and requiring an amputation or death during follow-up. Outcomes were analyzed by regression analysis, accounting for demographics, clinical characteristics, and antibiotic therapy.

Results

Among 147 outpatients with infected DFUs, 116 were included. Infections were categorized as mild (68%), moderate (26%), and severe (6%). Empirical antibiotics (not culture-guided) were prescribed as initial treatment in 39 individuals, while 77 received culture-based antibiotics. There were no differences in demographic or clinical characteristics between the antibiotic administration groups, except for a higher body mass index and prevalence of chronic kidney disease in the empirical cohort. Forty-two infected DFU patients required hospitalization within 30 days of diagnosis for the same reason. The relative risk for hospitalizations was 1.87 greater in those with mild infections when treated with empirical antibiotics compared with culture-directed antibiotics. There were no differences in amputations and/or death at 1 year follow-up.

Conclusions

These data support obtaining tissue culture to guide antibiotic therapy, regardless of DFU infection severity, to decrease hospitalizations.

Residual osteomyelitis at the resection margin after conservative surgery is not associated with the recurrence of diabetic foot infection and may successfully be treated without postoperative antibiotic therapy

AIMS

We hypothesize that microbiology- and pathology-confirmed positive bone margins after the resection of diabetes-related foot osteomyelitis are associated with worse outcomes.

METHODS

We conducted a prospective study consisting of a cohort of 93 patients with diabetes-related foot osteomyelitis (histopathology confirmed) who underwent bone resection and where an additional bone biopsy was taken at the resection margin. The primary outcome was the recurrence of the infection.

RESULTS

Pathology-confirmed positive margins were detected in 62 cases (66.7%), microbiology-confirmed positive margins were detected in 75 cases (80.6%) and recurrence was detected in 19 patients (20.4%). Chi-squared test failed to show the presence of an association between the recurrence of the infection with pathology-confirmed positive margins (p = 0.82), with microbiology-confirmed positive margins, (p = 0.34) and with the use of postoperative antibiotics (p = 0.70). Healing in patients with pathology-confirmed positive margins was achieved in a median of 12 weeks (95% CI 9.2-18) and those with pathology-confirmed negative margins in 14.9 weeks (95% CI 10.2-21.9), Log-rank test, p = 0.74. Thirty-four patients out of 61 available for follow-up (55.7%) with pathology-confirmed positive margins were treated without postoperative antibiotics. In that group, Chi-squared test failed to show the presence of an association between the recurrence of the infection with the use of postoperative antibiotics (p = 0.47).

CONCLUSIONS

A positive margin was neither associated with the recurrence of the infection nor with the time to healing. More than half of patients with pathology-confirmed positive margins were treated without postoperative antibiotics and this approach was not associated with the recurrence of the infection.

Retrospective study of outcomes of short versus long duration of antibiotic therapy for residual osteomyelitis in surgically resected diabetic foot infection

INTRODUCTION

Optimal treatment duration for residual osteomyelitis (OM) post-amputation in diabetic foot infection (DFI) remains unclear, with resultant heterogeneity in prescribing noted in clinical practice. We aimed to identify a difference in outcomes of long duration of antibiotics (LD) with short duration (SD) in patients with culture-positive proximal bone specimen post-amputation.

METHODS

In this single-centre retrospective cohort study (Melbourne, Australia), we analysed antibiotic duration of DFI patients requiring amputation with culture-positive proximal bone specimen over a 31 month period (January 2019-September 2021). Primary outcome was reamputation or debridement at the same and/or contiguous site of amputation at 6 months. Secondary outcomes were readmission to hospital and/or recommencement of antibiotics for DFI at the same and/or contiguous site at 6 months.

RESULTS

Among 92 patients (83% male, median age 67 years), 26 received <4 weeks (SD) and 66 received ≥4 weeks (LD) antibiotic therapy. In the SD group, primary outcome occurred in 9 patients (35%) compared with 15 patients (23%) in the LD group (P = 0.246). Both secondary outcomes occurred in 12 patients (46%) in the SD group compared with 18 patients (27%) in the LD group (P = 0.086). Adjusted logistic regression analysis showed SD was not significantly associated with primary outcome [OR 1.12 (95% CI 0.38-3.31)] or secondary outcomes [OR 1.67 (95% CI 0.60-4.66)].

CONCLUSIONS

This single-centre experience did not demonstrate significant difference in outcomes between antibiotic duration of <4 weeks and ≥4 weeks in DFI patients with culture-positive proximal bone specimen post-amputation. These data provide background for larger international randomized control trials to establish optimal treatment duration.

More Specialties, Fewer Problems: Using Collaborative Competency Between Infectious Diseases, Podiatry, and Pathology to Improve the Care of Patients with Diabetic Foot Osteomyelitis

BACKGROUND

Diabetic foot osteomyelitis is a common infection where treatment involves multiple services, including infectious diseases, podiatry, and pathology. Despite its ubiquity in the hospital, consensus on much of its management is lacking.

METHODS

Representatives from infectious diseases, podiatry, and pathology interested in quality improvement developed multidisciplinary institutional recommendations culminating in an educational intervention describing optimal diagnostic and therapeutic approaches to diabetic foot osteomyelitis (DFO). Knowledge acquisition was assessed by preintervention and postintervention surveys. Inpatients with forefoot DFO were retrospectively reviewed before and after intervention to assess frequency of recommended diagnostic and therapeutic maneuvers, including appropriate definition of surgical bone margins, definitive histopathology reports, and unnecessary intravenous antibiotics or prolonged antibiotic courses.

RESULTS

A postintervention survey revealed significant improvements in knowledge of antibiotic treatment duration and the role of oral antibiotics in managing DFO. There were 104 consecutive patients in the preintervention cohort (April 1, 2018, to April 1, 2019) and 32 patients in the postintervention cohort (November 5, 2019, to March 1, 2020), the latter truncated by changes in hospital practice during the coronavirus disease 2019 pandemic. Noncategorizable or equivocal disease reports decreased from before intervention to after intervention (27.0% versus 3.3%, respectively; P = .006). We observed nonsignificant improvement in correct bone margin definition (74.0% versus 87.5%; P = .11), unnecessary peripherally inserted central catheter line placement (18.3% versus 9.4%; P = .23), and unnecessary prolonged antibiotics (21.9% versus 5.0%; P = .10). In addition, by working as an interdisciplinary group, many solvable misunderstandings were identified, and processes were adjusted to improve the quality of care provided to these patients.

CONCLUSIONS

This quality improvement initiative regarding management of DFO led to improved provider knowledge and collaborative competency between these three departments, improvements in definitive pathology reports, and nonsignificant improvement in several other clinical endpoints. Creating collaborative competency may be an effective local strategy to improve knowledge of diabetic foot infection and may generalize to other common multidisciplinary conditions.

Outcomes of Hallux Amputation Versus Partial First Ray Resection in People with Non-Healing Diabetic Foot Ulcers: A Pragmatic Observational Cohort Study

There are few data comparing outcomes after hallux amputation or partial first ray resection after diabetic foot ulcer (DFU). In a similar context, the choice to perform one of these two surgeries is attributable to clinician preference based on experience and characteristics of the patient and the DFU. Therefore, the purpose of this study was to determine the more definitive surgery between hallux amputation and partial first ray resection. We abstracted data from a cohort of 70 patients followed for a 1-year postoperative period to support clinical practice. We also attempted to identify patient characteristics leading to these outcomes. Our results suggested no statistical difference between the type of surgery and outcomes such as recurrence of DFU and amputation at 3, 6, and 12 months or death. However, there was a statistically significantly increased likelihood of re-ulceration for patients with CAD who underwent hallux amputation (p = 0.02). There was also a significantly increased likelihood of re-ulceration for people with depression or a history when the partial ray resection was performed (p = 0.02). Patients with prior amputation showed a higher probability of undergoing another re-amputation with partial ray resection (p = 0.01). Although the trends that emerge from this project are limited to what is observed in this statistical context, where the number of patients included and the number of total observations per outcome were limited, it highlights interesting data for future research to inform clinical decisions to support best practices for the benefit of patients.

Lower extremity reamputation in people with diabetes: a systematic review and meta-analysis

In this study, we determined the reamputation-free survival to both limbs and to the contralateral limb only following an index amputation of any-level and assessed whether reamputation rates have changed over time. We completed a systematic search using PubMed and screened a total of 205 articles for data on reamputation rates. We reported qualitative characteristics of 56 studies that included data on reamputation rates and completed a meta-analysis on 22 of the studies which enrolled exclusively participants with diabetes. The random-effects meta-analysis fit a parametric survival distribution to the data for reamputations to both limbs and to the contralateral limb only. We assessed whether there was a temporal trend in the reamputation rate using the Mann-Kendall test. Incidence rates were high for reamputation to both limbs and to the contralateral limb only. At 1 year, the reamputation rate for all contralateral and ipsilateral reamputations was found to be 19% (IQR=5.1%-31.6%), and at 5 years, it was found to be 37.1% (IQR=27.0%-47.2%). The contralateral reamputation rate at 5 years was found to be 20.5% (IQR=13.3%-27.2%). We found no evidence of a trend in the reamputation rates over more than two decades of literature analyzed. The incidence of lower extremity reamputation is high among patients with diabetes who have undergone initial amputations secondary to diabetes, and rates of reamputation have not changed over at least two decades.

Multidrug resistant organism predicts ulcer recurrence following surgical management of diabetic foot osteomyelitis

Diabetic foot ulcers commonly precede diabetic foot osteomyelitis (DFO) and once the latter occurs, surgical management is often performed. The presence of osteomyelitis is an independent risk factor for the development of re-ulceration. We investigated the relationship between causative organisms in osteomyelitis and 1-year diabetic foot outcomes (re-ulceration, amputation, and death) following surgical management in an observational cohort of 223 patients. Univariate and multivariate analyses were performed for available demographic, clinical, and laboratory data. In addition, random forest plots were used to identify microbiologic predictors of 1-year outcomes. Patients with osteomyelitis managed surgically were younger and exhibited more painful peripheral neuropathy than outpatients with diabetes alone (both P < .0001). Osteomyelitis proximal margin cultures were diverse, at times polymicrobial, and included multidrug-resistant organisms in 13.9% of the cohort. In patients who underwent surgery, 44.5% experienced a re-ulceration on the same foot within 12 months of surgery. The presence of multidrug-resistant organisms on proximal bone culture was found to be a significant predictor of diabetic foot ulcer recurrence in univariate modelling (P < .001) and importance rankings. This is the first study to use prediction modelling to identify a relationship between multidrug-resistant organisms and diabetic foot ulcer recurrence following DFO.

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.

Making the equivocal unequivocal: standardization of clean margins in diabetic foot osteomyelitis

Background

The prevalence of diabetes mellitus continues to rise. Diabetic foot ulcers with osteomyelitis are a diabetes-related complication presenting a significant burden to this cohort. A cure to diabetic foot osteomyelitis remains elusive and standard of care has failed to improve outcomes. To advance research and better patient outcomes, the authors offer specific guidance with terminology to enhance operative dictations which may improve surgical practice and guide treatment.

Methods

A consecutive review of podiatric surgical dictations for inpatient diabetic foot osteomyelitis within a tertiary care facility was performed. Surgical descriptors of bone were standardized: density, anatomic structure, vascular thrombosis, color, and draining sinus. Correlations between the five categories and histopathological results were performed after kappa analysis for interrater reliability was performed.

Results

Kappa coefficient demonstrated high inter-reliability of surgical findings. This suggests potential agreement amongst surgeons performing similar procedures. It was also found that specific bone descriptors had moderate to strong correlation with clean histopathologic bone margins when biopsied. This further suggests that the use of standardized terms may help guide definitive therapy.

Conclusions

The authors suggest a standardized approach which includes consistent descriptors of intraoperative bone. With use of standardized terms, vague and blanket descriptors are eliminated. This has potential to improve understanding of changes within bone as a result of infection and diabetes. Early and improved communication of intraoperative findings will enhance the multidisciplinary approach. This could potentially lead to changes in diabetic foot management and may limit hospital waste waiting for final cultures and pathology reports.

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.

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.

Fungal Osteomyelitis in Diabetic Foot Infections: A Case Series and Comparative Analysis

Fungal osteomyelitis (OM) is relatively rare. There is scarce literature discussing fungal OM in diabetic foot infections (DFIs). This case series explores the clinical characteristics of patients treated at a large tertiary academic center for DFI and found to have a causative agent of fungal origin in their bone on surgical intervention. Between July 2017 and March 2018, a prospective longitudinal analysis was performed of patients with diabetes admitted to our institution who underwent operative management of OM. Demographic, clinical, radiographic, and laboratory data were collected for all patients. Data between bacterial and fungal OM cohorts was analyzed for differences and similarities in patient characteristics and outcomes. All patients were followed 20 weeks postoperatively. Five patients with fungal OM were identified from the 35 cases where OM was confirmed through podiatric surgical intervention. In each fungal case, a Candida species was isolated from operative bone culture which included subspecies Candida albicans, C parapsilosis, and C glabrata. A P value ⩾.05 was found in clinical characteristics between our cohorts. Wound healing was achieved in 40% of patients with fungal OM, and oral fluconazole successfully treated Candida OM in the cases that achieved healing. Diabetes can increase the risk of Candida OM. In DFIs, fungus can impede wound healing if not recognized and treated. Because Candida OM is typically indolent in nature, bone biopsy and mycological culture is recommended for definitive diagnosis and treatment.