Are diabetic foot ulcers complicated by MRSA osteomyelitis associated with worse prognosis? Outcomes of a surgical series

Influence of Staphylococcus aureus Infection on Partially Ischemic Excisional Skin Wounds

Background

Skin wounds, whether medically or incidentally induced, are always at a risk of becoming infected, but the infection risks are greater when the wounds are recovering under ischemic, poorly perfused conditions. Staphylococcus aureus, which frequently infects cutaneous and soft tissue, can infect to a greater extent when wounds are poorly perfused. Bad as this may be, both MSSA and MRSA strains of S. aureus can cause severe infections, with MRSA being considered more aggressive.

Methods

In this study, we used a lagomorph ear excisional wound model to initially test the influence of partial ischemia on uninfected wound healing. We then subsequently test the same ischemic injury model under an active MSSA infection and compared these wounds against normally perfused MSSA-infected wounds. Lastly, we test whether differences in healing exist between MSSA-infected and MRSA-infected wounds, both under the same ischemic model.

Results

The data suggest that partial ischemia considerably reduces healing of noninfected wounds (epithelial gap P=∗∗∗∗, granulation gap P=∗∗∗, and granulation area P=∗∗∗∗). Similarly, partial ischemic wounds coupled with MSSA infection display healing impairments against likewise-infected wounds healing under normal perfusion (epithelial gap P=∗, granulation gap P=∗, and granulation area P=∗∗). No significant differences were observed between MSSA-infected and MRSA-infected wounds healing under ischemia.

Conclusion

The data produced quantitative differences in healing under various conditions consequent to ischemia and S. aureus infection. Although it is well recognized that ischemia and infection adversely influence healing, by testing these conditions, we determined the detrimental magnitude such circumstances inflict on skin healing, thereby providing a relative reference to compare and gauge when met with similar conditions clinically.

Community-associated methicillin-resistant Staphylococcus aureus infection of diabetic foot ulcers in an eastern diabetic foot center in a tertiary hospital in China: a retrospective study

BACKGROUND

Diabetic foot concerns are a major public health problem. Methicillin-resistant Staphylococcus aureus (MRSA) plays a significant role in diabetic foot ulcers. Community-associated MRSA has become notorious for skin and skin soft tissue infections over the last two decades. This study investigated MRSA infection in diabetic foot patients at a tertiary hospital, focusing on the epidemiology and characteristics of community-associated MRSA.

METHODS

A total of 149 patients with diabetic foot infection whose culture results indicated Staphylococcus aureus as the source were selected. Epidemiological investigations, clinical characteristics, laboratory index records, antibiotic susceptibility analysis, and clinical outcome tracking were performed in all cases. Based on oxacillin resistance using the Vitek Compact 2 system, cases were divided into methicillin-sensitive Staphylococcus aureus and MRSA groups. Subgroup analysis of the MRSA group was performed in accordance with the Centers for Disease Control definition: community-associated MRSA and hospital-associated MRSA.

RESULTS

The MRSA group (n = 41, 27.5%) had a longer duration of ulcers and hospital stay and higher hospitalization costs than the methicillin-sensitive Staphylococcus aureus group (n = 108, 72.5%). According to the classification criteria of Infectious Diseases Society of America, the severity of infection in the community-associated MRSA group was higher than that in the hospital-associated MRSA group. The analysis of antimicrobial susceptibility of 41 MRSA isolates showed that the resistance rates to erythromycin, clindamycin, quinolone, gentamicin, tetracycline, and rifampicin were 78.0%, 68.3%, 31.7%, 17.1%, 9.8%, and 2.4%, respectively. All the MRSA strains were sensitive to linezolid, tigecycline, and vancomycin. The resistance rates to quinolones and gentamycin in the community-associated MRSA group (both 0%) were lower than those in the hospital-associated MRSA group.

CONCLUSION

Emergence of MRSA in diabetic foot ulcer was associated with a prolonged wound duration and increased consumption of medical resources. Community-associated MRSA strains predominated among MRSA isolates from diabetic foot wounds and caused more severe infections.

Management patterns and outcomes of patients hospitalized with diabetic foot ulcers at one tertiary care hospital

A diabetic foot ulcer is present in approximately 2.4% of hospitalized patients. Care for diabetic foot ulcers is highly variable. We sought to describe care practice patterns and risk factors for poor outcomes for patients hospitalized with a diabetic foot ulcer in our institution, an 894-bed tertiary care academic hospital located in downtown Chicago, IL. We conducted a retrospective cohort study of patients hospitalized with a diabetic foot ulcer between March 3rd, 2018 and December 31st, 2019. We categorized patients into having an uncomplicated ulcer or a complicated ulcer with cellulitis, wound infection, osteomyelitis, or gangrene. We evaluated rates of diagnostic resource utilization (imaging, cultures, biopsies, and antibiotics) and outcomes of osteomyelitis, amputation, and death. There were 305 patients of interest in the study cohort. A complicated lower extremity ulcer was found in 79% of patients. Amputation was required in 25% of patients, 21% were readmitted, and 13% died. Imaging was obtained in less than 50% of all patients, and in 60% or less of those with osteomyelitis. Bone biopsies were rarely acquired. Empiric antibiotics were prescribed in 77% of patients with osteomyelitis. Male, Black or African-American patients, and those with high Charlson score had the highest risk of poor outcomes. Care practices for patients hospitalized with diabetic foot ulcers were highly variable. Future interventions should target standardization to improve outcomes, with particular attention to health inequities as vulnerable populations have a higher risk of poor outcomes.

Polymicrobial Foot Infection Patterns Are Common and Associated With Treatment Failure

BACKGROUND

That foot infections are predominately polymicrobial has long been recognized, but it is not clear if the various species co-occur randomly or in patterns. We sought nonrandom species co-occurrence patterns that might help better predict prognosis or guide antimicrobial selection.

METHODS

We analyzed tissue (bone, skin, and other soft tissue), fluid, and swab specimens collected from initial foot infection episodes during a 10-year period using a hospital registry. Nonrandom co-occurrence of microbial species was identified using simple pairwise co-occurrence rates adjusted for multiple comparisons, Markov and conditional random fields, and factor analysis. A historical cohort was used to validate pattern occurrence and identify clinical significance.

RESULTS

In total, 156 unique species were identified among the 727 specimens obtained from initial foot infection episodes in 694 patients. Multiple analyses suggested that Staphylococcus aureus is negatively associated with other staphylococci. Another pattern noted was the co-occurrence of alpha-hemolytic Streptococcus, Enterococcus fecalis, Klebsiella, Proteus, Enterobacter, or Escherichia coli, and absence of both Bacteroides and Corynebacterium. Patients in a historical cohort with this latter pattern had significantly higher risk-adjusted rates of treatment failure.

CONCLUSIONS

Several nonrandom microbial co-occurrence patterns are frequently seen in foot infection specimens. One particular pattern with many Proteobacteria species may denote a higher risk for treatment failure. Staphylococcus aureus rarely co-occurs with other staphylococci.

Meta-Analysis: Outcomes of Surgical and Medical Management of Diabetic Foot Osteomyelitis

BACKGROUND

The aim of this study was to evaluate clinical outcomes in the published literature on medical and surgical management of diabetic foot osteomyelitis (DFO).

METHODS

A PubMed and Google Scholar search of articles relating to DFO was performed over the dates of January 1931 to January 2020. Articles that involved Charcot arthropathy, case reports, small case series, review articles, commentaries, nonhuman studies, and non-English articles were excluded. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to rate the bias of each study. A meta-analysis was performed using random-effects and inverse variance methods. The search yielded 1192 articles. After review and the removal of articles that did not meet inclusion criteria, 28 articles remained. Eighteen articles were related to the medical management of DFO and 13 articles were related to surgical management. Three articles looked at a combination of medical and surgical management and were included in both groups. Heterogeneity was evaluated using Cochran Q, I 2, τ2, and τ.

RESULTS

The average success rate was 68.2% (range, 17.0%-97.3%) for medical treatment and 85.7% (range, 65.0%-98.8%) for surgical and medical treatment. There were significant inconsistencies in accounting for peripheral arterial disease and peripheral neuropathy. There was significant heterogeneity in outcomes between studies. However, there was a high rate of successful treatment and a wide range between patients with medical treatment and combined surgical and medical treatment.

CONCLUSIONS

Additional properly designed prospective studies with gold-standard references for diagnosing osteomyelitis are needed to help determine whether medical management of DFO can be successful without surgical intervention.

Comparative Clinical Outcomes of Patients with Diabetic Foot Infection Caused by Methicillin-Resistant Staphylococcus Aureus (MRSA) or Methicillin-Sensitive Staphylococcus Aureus (MSSA)

Few studies have addressed the interaction of specific pathogens with clinical outcomes in patients with diabetic foot infection (DFI). Our study aim was to compare the clinical outcomes among patients with DFI caused by methicillin-resistant Staphylococcus aureus (MRSA) with cases caused by methicillin-sensitive Staphylococcus aureus (MSSA). We gathered the data of 75 consecutive patients admitted at specialized outpatients diabetic with mild or moderate DFI in which S. aureus was isolated from bone or soft tissue specimens in pure or as a part of the polymicrobial culture. Patients were divided into two groups: those with MRSA infection and those with MSSA infection. Patients with MRSA diabetic foot infections were significantly associated with male gender (86% vs. 64%, P = .029), higher SINBAD Classification Score (3.6 ± 0.99 points vs. 2.8 ± 1.06 points, P = .001), longer mean wound evolution [17.8 (3;29.5) weeks versus 9.1 (1;12) weeks, P = .008], bone involvement [18 (50%) versus 9 (23.1%), P = .015] and longer mean healing time [18.2(8;28) weeks versus 9.1 (1;12) weeks, P = .008]. In addition, male gender (OR 8.81, 95% CI 2.00-38.84) and SINBAD Classification Score (OR 2.70, 1.46-5.00) were identified as independent risk factors for MRSA DFI. Significant differences in the number of surgical procedures to resolve infection [15 (41.7%) versus 13 (33.3%), P = .456] or in the mean healing time after surgical treatment [10.5 weeks (6.7;16.5) versus 6.1 weeks (3;8.7), P = .068] were not observed among groups, suggesting that when treatment is based on early and surgical debridement, MRSA infections are not associated with worse prognosis. In conclusion MRSA DFI has importance in clinical outcomes such as time to healing. We propose that recent lines of research regarding the genetic virulence of strains of S. aureus could provide new insights into our results.

Ceramic composite with gentamicin decreases persistent infection and increases bone formation in a rat model of debrided osteomyelitis

Introduction: Current methods of managing osteomyelitic voids after debridement are inadequate and result in significant morbidity to patients. Synthetic ceramic void fillers are appropriate for non-infected bone defects but serve as a nidus of re-infection in osteomyelitis after debridement. CERAMENT G (CG) is an injectable ceramic bone void filler which contains gentamicin and is currently being evaluated for use in osteomyelitic environments after debridement due to its theoretical ability to serve as a scaffold for healing while eliminating residual bacteria after debridement through the elution of antibiotics. The goal of this study was to evaluate (1) the rate of persistent infection and (2) new bone growth of a debrided osteomyelitic defect in a rat model which has been treated with either gentamicin-impregnated ceramic cement (CERAMENT G) or the same void filler without antibiotics (CERAMENT, CBVF). Methods: Osteomyelitis was generated in the proximal tibia of Sprague Dawley rats, subsequently debrided, and the defect filled with either (1) CG ( n = 20 ), (2) CBVF ( n = 20 ), or (3) nothing ( n = 20 ). Each group was euthanized after 6 weeks. Infection was detected through bacterial culture and histology. Bone growth was quantified using microCT. Results: Infection was not detected in defects treated with CG as compared with 35 % of defects ( 7 / 20 ) treated with CBVF and 50 % ( 10 / 20 ) of empty defects ( p = 0.001 ). Bone volume in the defect of CG-treated rats was greater than the CBVF (0.21 vs. 0.17, p = 0.021 ) and empty groups (0.21 vs. 0.11, p < 0.001 ) at 6 weeks after implantation. Conclusions: Ceramic void filler with gentamicin (CERAMENT G) decreased the rate of persistent infection and increased new bone growth as compared to the same void filler without antibiotics (CERAMENT) and an empty defect in a rat model of debrided osteomyelitis.

The Effects of Antimicrobial Resistance and the Compatibility of Initial Antibiotic Treatment on Clinical Outcomes in Patients With Diabetic Foot Infection

We aimed to determine pathogen microorganisms, their antimicrobial resistance patterns, and the effect of initial treatment on clinical outcomes in patients with diabetic foot infection (DFI). Patients with DFI from 5 centers were included in this multicenter observational prospective study between June 2018 and June 2019. Multivariate analysis was performed for the predictors of reinfection/death and major amputation. A total of 284 patients were recorded. Of whom, 193 (68%) were male and the median age was 59.9 ± 11.3 years. One hundred nineteen (41.9%) patients had amputations, as the minor (n = 83, 29.2%) or major (n = 36, 12.7%). The mortality rate was 1.7% with 4 deaths. A total of 247 microorganisms were isolated from 200 patients. The most common microorganisms were Staphylococcus aureus (n = 36, 14.6%) and Escherichia coli (n = 32, 13.0%). Methicillin resistance rates were 19.4% and 69.6% in S aureus and coagulase-negative Staphylococcus spp., respectively. Multidrug-resistant Pseudomonas aeruginosa was detected in 4 of 22 (18.2%) isolates. Extended-spectrum beta-lactamase-producing Gram-negative bacteria were detected in 20 (38.5%) isolates of E coli (14 of 32) and Klebsiella spp. (6 of 20). When the initial treatment was inappropriate, Klebsiella spp. related reinfection within 1 to 3 months was observed more frequently. Polymicrobial infection (p = .043) and vancomycin treatment (p = .007) were independent predictors of reinfection/death. Multivariate analysis revealed vascular insufficiency (p = .004), hospital readmission (p = .009), C-reactive protein > 130 mg/dL (p = .007), and receiving carbapenems (p = .005) as independent predictors of major amputation. Our results justify the importance of using appropriate narrow-spectrum empirical antimicrobials because higher rates of reinfection and major amputation were found even in the use of broad-spectrum antimicrobials.

Outcomes after Emergency Admission with a Diabetic Foot Attack Indicate a High Rate of Healing and Limb Salvage But Increased Mortality: 18-Month Follow-up Study

AIM

The diabetic foot attack (DFA) is perhaps the most devastating form of diabetic foot infection, presenting with rapidly progressive skin and tissue necrosis, threatening both limb and life. However, clinical outcome data in this specific group of patients are not available.

METHODS

Analysis of 106 consecutive patients who underwent emergency hospitalisation for DFA (TEXAS Grade 3B or 3D and Infectious Diseases Society of America (IDSA) Class 4 criteria). Outcomes evaluated were: 1) Healing 2) major amputation 3) death 4) not healed. The first outcome reached in one of these four categories over the follow-up period (18.4±3.6 months) was considered. We also estimated amputation free survival.

RESULTS

Overall, 57.5% (n=61) healed, 5.6% (n=6) underwent major amputation, 23.5% (n=25) died without healing and 13.2% (n=14) were alive without healing. Predictive factors associated with outcomes were: Healing (age<60, p=0.0017; no Peripheral arterial disease (PAD) p= 0.002; not on dialysis p=0.006); major amputation (CRP>100 mg/L, p=0.001; gram+ve organisms, p=0.0013; dialysis, p= 0.001), and for death (age>60, p= 0.0001; gram+ve organisms p=0.004; presence of PAD, p=0.0032; CRP, p=0.034). The major amputation free survival was 71% during the first 12 months from admission, however it had reduced to 55.4% by the end of the follow-up period.

CONCLUSIONS

In a unique population of hospitalised individuals with DFA, we report excellent healing and limb salvage rates using a dedicated protocol in a multidisciplinary setting. An additional novel finding was the concerning observation that such an admission was associated with high 18-month mortality, almost all of which was after discharge from hospital.

Virulence Factor Genes in Staphylococcus aureus Isolated From Diabetic Foot Soft Tissue and Bone Infections

The aim of this study is to describe the presence of genes encoding for 4 virulence factors (pvl, eta, etb, and tsst), as well as the mecA gene conferring resistance to beta-lactam antibiotics, in patients with diabetes and a staphylococcal foot infection. We have also analyzed whether isolates of Staphylococcus aureus from bone infections have a different profile for these genes compared with those from exclusively soft tissue infections. In this cross-sectional study of a prospectively recruited series of patients admitted to the Diabetic Foot Unit, San Juan de Dios Hospital, San José, Costa Rica with a moderate or severe diabetic foot infection (DFI), we collected samples from infected soft tissue and from bone during debridement. During the study period (June 1, 2014 to May 31, 2016), we treated 379 patients for a DFI. S aureus was isolated from 101 wound samples, of which 43 were polymicrobial infections; we only included the 58 infections that were monomicrobial S aureus for this study. Infections were exclusively soft tissue in 17 patients (29.3%) while 41 (70.7%) had bone involvement (osteomyelitis). The mecA gene was detected in 35 cases (60.3%), pvl gene in 4 cases (6.9%), and tsst gene in 3 (5.2%). We did not detect etA and etB in any of the cases. There were no differences in the profile of S aureus genes encoding for virulence factors (pvl, etA, etB, and tsst) recovered from DFIs between those with just soft tissue compared to those with osteomyelitis. However, we found a significantly higher prevalence of pvl+ strains of S aureus associated with soft tissue compared with bone infections. Furthermore, we observed a significantly longer time to healing among patients infected with mecA+ (methicillin-resistant) S aureus (MRSA).

Modern management of diabetic foot osteomyelitis. The when, how and why of conservative approaches

INTRODUCTION

Diabetic foot osteomyelitis (DFO) has long been considered a complex infection that is both difficult to diagnose and treat, and is associated with a high rate of relapse and limb loss. Areas covered: DFO can usually be diagnosed by a combination of clinical evaluation, serum inflammatory markers and plain X-ray. When the results of these procedures are negative or contradictory, advanced imaging tests or bone biopsy may be necessary. Staphylococcus aureus remains the most frequent microorganism isolated from bone specimens, but infection is often polymicrobial. Antibiotic therapy, preferably with oral agents guided by results of bone culture, for a duration of no more than six weeks, appears to be as safe and effective as surgery in cases of uncomplicated forefoot DFO. Surgery (which should be limb-sparing when possible) is always required for DFO accompanied by necrotizing fasciitis, deep abscess, gangrene or in cases not responding (either clinically or radiographically) to apparently appropriate antibiotic treatment. Expert commentary: Research in the past decade has improved diagnosis and treatment of DFO, and most cases can now be managed with a 'conservative' approach, defined as treatment either exclusively with antibiotics or with surgery removing as little bone and soft tissue as necessary.

Methicillin-Resistant Staphylococcus aureus in Foot Osteomyelitis

BACKGROUND

Conflicting studies exist regarding the impact of methicillin-resistant Staphylococcus aureus (MRSA) on increased time to wound healing, future need for surgical procedures, and likelihood of treatment failure in patients with diabetic foot osteomyelitis. The purpose of this study is to determine the overall significance of MRSA in predicting treatment failure in bone infections of the foot and to determine an appropriate pre-operative and empiric post-operative antibiotic regimen.

PATIENTS AND METHODS

Patients presenting with an initial episode of "probable" or "definite" foot osteomyelitis were included for review and analysis if the following criteria were met: (1) Osteomyelitis occurred in the foot (i.e., distal to the malleoli of the ankle); episodes occurring above the ankle were excluded. (2) Patients received either no antibiotics or only oral antibiotics for long-term treatment; episodes managed with long-term parenteral antibiotics were excluded. (3) The infection was managed initially with medical therapy or conservative surgical therapy; episodes managed with major (above-ankle) amputation as the initial treatment were excluded. The primary objective of this study was to assess whether episodes of foot osteomyelitis associated with MRSA resulted in treatment failure more frequently than not.

RESULTS

Of 178 episodes included in the study, 50 (28.1%) episodes had treatment failure. Median time-to-treatment failure was 60 days (range 7-598 days). In 28.1% (9/32 episodes) in which treatment failure occurred and 39.0% (41/105) episodes in which no treatment failure occurred, MRSA was present. The presence of MRSA was not significantly associated with treatment failure (p = 0.99).

CONCLUSIONS

The presence of MRSA in bone culture and whether antibiotic use had anti-MRSA activity was not associated with increased treatment failure of diabetic foot osteomyelitis in our institution. Empiric antibiotic coverage of MRSA may not be necessary for many patients presenting with foot osteomyelitis.

Treatment Failure and Leg Amputation Among Patients With Foot Osteomyelitis

We sought to identify factors associated with treatment failure and leg amputations among those patients who presented with foot osteomyelitis. Characteristics, treatments, and outcomes for all patients treated for probable or definite foot osteomyelitis (per consensus definition) between January 2011 and March 2015 were reviewed. Multivariate Cox regression models were used to identify risk factors for treatment failure (unanticipated resection of additional bone or leg amputation) and of leg amputation alone. A total of 184 episodes of foot osteomyelitis met inclusion criteria. Treatment failure occurred in 53 (28.8%) and leg amputation in 21 (11.4%). Risk factors for treatment failure included severe/unaddressed peripheral artery disease, homelessness, Pseudomonas aeruginosa or Escherichia coli bone isolates, serum albumin <2.8 mg/dL, hallux involvement, insulin therapy, 60 or more pack-years smoking, and <7 days of directed antibiotic therapy for a positive bone margin. Delayed primary wound closure (ie, staged operations) had significantly lower treatment failure risk. Unanticipated resection of bone was not associated with leg amputation. Foot osteomyelitis treatment failure is common. Various factors can help identify those at risk for treatment failure and/or leg amputation, and further studies should focused whether initial management or follow-up should change when these factors are present.

Epidemiology of Methicillin-Resistant Staphylococcus aureus Diabetic Foot Infections in a Large Academic Hospital: Implications for Antimicrobial Stewardship

Introduction

Diabetic foot infections (DFIs) are the leading cause of non-traumatic lower extremity amputations in the United States. Antimicrobials active against methicillin-resistant Staphylococcus aureus (MRSA) are recommended in patients with associated risk factors; however, limited data exist to support these recommendations. Due to the changing epidemiology of MRSA, and the consequences of unnecessary antibiotic therapy, guidance regarding the necessity of empirical MRSA coverage in DFIs is needed. We sought to 1) describe the prevalence of MRSA DFIs at our institution and compare to the proportion of patients who receive MRSA antibiotic coverage and 2) identify risk factors for MRSA DFI.

Methods

This was a retrospective cohort study of all adult, culture-positive DFI patients managed at University Hospital, San Antonio, TX between January 1, 2010 and September 1, 2014. Patient eligibility included a principal ICD-9-CM discharge diagnosis code for foot infection and a secondary diagnosis of diabetes. The primary outcome was MRSA identified in the wound culture. Independent variables assessed included patient demographics, comorbidities, prior hospitalization, DFI therapies, prior antibiotics, prior MRSA infection, and laboratory values. Multivariable logistic regression was used to identify risk factors for MRSA DFI.

Results

Overall, 318 patients met inclusion criteria. Patients were predominantly Hispanic (79%) and male (69%). Common comorbidities included hypertension (76%), dyslipidemia (52%), and obesity (49%). S. aureus was present in 46% of culture-positive DFIs (MRSA, 15%). A total of 273 patients (86%) received MRSA antibiotic coverage, resulting in 71% unnecessary use. Male gender (OR 3.09, 95% CI 1.37–7.99) and bone involvement (OR 1.93, 1.00–3.78) were found to be independent risk factors for MRSA DFI.

Conclusions

Although MRSA was the causative pathogen in a small number of DFI, antibiotic coverage targeted against MRSA was unnecessarily high.

Optimising the quality and outcomes of treatments for diabetic foot infections

INTRODUCTION

Infection is the commonest foot complication that arises in people with diabetes and may lead to amputation and even death. The emergence of multidrug resistant bacteria, especially in Gram negative rods, may have a negative impact on the chances of cure in these patients.

AREAS COVERED

We searched the Medline and Pubmed databases for studies using the keywords 'diabetic foot infection' and 'diabetic foot osteomyelits' from 1980 to 2016. Expert commentary: Much has been done in the field of diabetic foot infection regarding pathophysiology, diagnosis and treatment. The construction of multidisciplinary teams is probably the most efficient way to improve the patients' outcome. The rational use of antibiotics and surgical skills are essential in these potentially severe infections. Each case of diabetic infection deserves to be discussed in the light of the current guidelines and the local resources. Because of the overal poor outcome of these infections, prevention remains a priority.

Staphylococcus aureus Toxins and Diabetic Foot Ulcers: Role in Pathogenesis and Interest in Diagnosis

Infection of foot ulcers is a common, often severe and costly complication in diabetes. Diabetic foot infections (DFI) are mainly polymicrobial, and Staphylococcus aureus is the most frequent pathogen isolated. The numerous virulence factors and toxins produced by S. aureus during an infection are well characterized. However, some particular features could be observed in DFI. The aim of this review is to describe the role of S. aureus in DFI and the implication of its toxins in the establishment of the infection. Studies on this issue have helped to distinguish two S. aureus populations in DFI: toxinogenic S. aureus strains (harboring exfoliatin-, EDIN-, PVL- or TSST-encoding genes) and non-toxinogenic strains. Toxinogenic strains are often present in infections with a more severe grade and systemic impact, whereas non-toxinogenic strains seem to remain localized in deep structures and bone involving diabetic foot osteomyelitis. Testing the virulence profile of bacteria seems to be a promising way to predict the behavior of S. aureus in the chronic wounds.

Six-week versus twelve-week antibiotic therapy for nonsurgically treated diabetic foot osteomyelitis: a multicenter open-label controlled randomized study

OBJECTIVE

Little is known about the optimal duration of antibiotic therapy for diabetic foot osteomyelitis (DFO). This study sought to compare the effectiveness of 6 versus 12 weeks of antibiotic therapy in patients with DFO treated nonsurgically (i.e., antibiotics alone).

RESEARCH DESIGN AND METHODS

This was a prospective randomized trial comparing 6- versus 12-week duration of antibiotic treatment. Remission of osteomyelitis during the monitoring period was defined as complete and persistent (>4 weeks) healing of the wound (if present initially), absence of recurrent infection at the initial site or that of adjacent rays, and no need for surgical bone resection or amputation at the end of a follow-up period of at least 12 months after completion of antibiotic treatment.

RESULTS

Forty patients followed at five French general hospitals were randomized between January 2007 and January 2009, with 20 treated for 6 weeks and 20 treated for 12 weeks with antibiotics. The two groups were comparable for all variables recorded at inclusion in the study. Remission was obtained in 26 (65%) patients, with no significant differences between patients treated for 6 versus 12 weeks (12/20 vs. 14/20, respectively; P = 0.50). We did not identify any significant parameters associated with patient outcome. Fewer patients treated for 6 weeks experienced gastrointestinal adverse events related to antimicrobial therapy compared with patients treated for 12 weeks (respectively, 15 vs. 45%; P = 0.04).

CONCLUSIONS

The present multicenter prospective randomized study provides data suggesting that 6-week duration of antibiotic therapy may be sufficient in patients with DFO for whom nonsurgical treatment is considered.

Staphylococcus aureus–Related Diabetic Osteomyelitis

Staphylococcus aureus is the main cause of diabetic foot osteomyelitis (DFO) and can be treated medically or by surgery. We investigated the outcome of consecutive patients with a diagnosis of S aureus DFO retrospectively in 4 hospitals according to the type of management, medical (including debridement at bedside) or surgical. The outcome was classified as either favorable or failure (relapse, impaired wound healing, or amputation). Seventy-four patients with S aureus DFO, including 26 with methicillin-resistant S aureus, were included with a mean duration of follow-up of 21 ± 1 months. As part of the initial treatment, 47% underwent bone surgery followed with a short course of antibiotic. Others were treated with antibiotic therapy alone with bedside debridement. The outcome was favorable for 84% of these patients, with similar rates in the surgical and medical groups (80% vs 87%, P > .05). Patients in the medical group were less frequently hospitalized (49% vs 94%, P < .001) and had a shorter length of hospital stay (17 ± 3 vs 50 ± 12 days, P = .004). Patients in the surgery group received a shorter course of antibiotic therapy (10 ± 2 vs 11 ± 1 weeks, P = .001) with fewer side effects (9% vs 33%, P = .01). The type of management was not associated with subsequent new episode of noncontiguous DFO, which developed in 32% of cases. In conclusion, except significant differences in duration of hospitalization and antibiotic therapy, medical and surgical management of S aureus DFO had similar outcomes with a cure rate >80%.

Do Diabetic Foot Infections With Methicillin-Resistant Staphylococcus aureus Differ From Those With Other Pathogens?

There is controversy as to whether or not diabetic foot infections (DFIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) are associated with worse outcomes than DFIs caused by other pathogens. To address this issue we performed a nonsystematic literature search of published articles in English language journals seeking studies reporting on the outcomes of DFIs related to their microbiology. We retrieved 48 articles published from 1999 to 2013 that described a total of 7771 cases of DFI. The overall proportion of DFIs with an isolate of S aureus was about 30%; just over one third of these (11% of all cases) were MRSA strains. Among the DFI cases caused by MRSA 1543 were episodes of soft tissue infections and 113 of osteomyelitis, while non-MRSA organisms caused 5761 soft tissue infections and 354 cases of osteomyelitis. Only 5 of the included articles attempted a comparison between DFI caused by MRSA and those caused by other pathogens, with no clear differences noted. The median total duration of antibiotic therapy for DFI caused by MRSA was 26 days, of which a median of 10 days was given intravenously. Only a few articles reported the proportion of patients with a recurrence, but they often did not differentiate between MRSA and non-MRSA cases. Four publications reported a worse functional or microbiological outcome in MRSA, compared to non-MRSA, cases, but the findings were variable and differences did not seem to be significant. Many trials failed to adjust for case-mix or to definitively demonstrate a relationship between microbiology and outcomes. Few of the articles specifically commented on whether the MRSA isolates were health care- or community-acquired strains. Notwithstanding the substantial limitations of the available literature, there does not appear to be a need for any special treatment for DFI caused by MRSA. The current guidelines for treating according to established international recommendations seem appropriate.

Osteomyelitis of the foot and ankle: diagnosis, epidemiology, and treatment

Osteomyelitis of the foot and ankle is a common, potentially devastating condition with diagnostic and treatment challenges. Understanding the epidemiology and pathogenesis of osteomyelitis can raise clinical suspicion and guide testing and treatments. History and physical examination, laboratory studies, vascular studies, histologic and microbiologic analyses, and various imaging modalities contribute to diagnosis and treatment. Treatment including empiric broad-spectrum antibiotics and surgery should take a multidisciplinary approach to optimize patient factors, ensure eradication of the infection, and restore function. Optimization of vascular status, soft tissues, limb biomechanics, and physiologic state of the patient must be considered to accelerate and ensure healing.

Risk factors for methicillin-resistant Staphylococcus aureus in diabetic foot infections

Objective

The purpose of this study was to evaluate risk factors for methicillin-resistant Staphylococcus aureus (MRSA) in patients hospitalized for diabetic foot infections.

Methods

We reviewed hospital admissions for foot infections in patients with diabetes which had nasal swabs, and anaerobic and aerobic tissue cultures at the time of admission. Data collected included patient characteristics and medical history to determine risk factors for developing an MRSA infection in the foot.

Results

The prevalence of MRSA in these infections was 29.8%. Risk factors for MRSA diabetic foot infections were history of MRSA foot infection, MRSA nasal colonization, and multidrug-resistant organisms (p<0.05). Positive predictive value (PPV) and negative predictive value (NPV) of nasal colonization with MRSA to identify MRSA diabetic foot infections were 66.7% and 80.0% (sensitivity 41%, specificity 90%). Admission from a nursing home was not a significant risk factor.

Conclusion

Positive nasal swabs are not predictive of the infecting agent; however, a negative nasal swab rules out MRSA as the infecting agent in foot wounds with 90% accuracy.

Revision Surgery for Diabetic Foot Infections

Revision surgery (RS) is frequently needed to control diabetic foot infections. It is the aim of this retrospective observational study to analyze the variables associated with undergoing RS and the variables associated with undergoing a major amputation when RS was required. We conducted a retrospective study of patients with diabetes treated in our department during 10 years (January 1, 2000 to January 1, 2010) who had foot infections identifying those who required RS. In all, 167 out of 417 patients (40%) with diabetes who underwent surgery for foot infections underwent RS for persistent infection. The predictive variables related to undergoing revision surgery were erythrocyte sedimentation rate >70 mm/h (odds ratio [OR] = 1.6, 95% confidence interval [CI] = 1.1-2.6), leukocytosis (OR = 1.6, 95% CI = 1.1-2.5), peripheral arterial disease (OR = 1.5, 95% CI = 1.0-2.4), and isolation of gram-negative rods from tissue biopsy (OR = 2.2, 95% CI = 1.5-3.4). Seventy-nine out of 167 patients (47.3) who underwent RS required a higher level of surgery achieving a limb salvage rate of 70.7%. Predictive variables related to undergoing a major amputation after RS were persistent infection located in the bone (OR = 0.08, 95% CI = 0.03-0.22), ischemic heart disease (OR = 3.4, 95% CI = 1.4-8.5), 2 or more reoperations (OR = 3.0, 95% CI = 1.2-7.1), isolation of gram-negative rods from tissue biopsy (OR = 3.3, 95% CI = 1.3-8.4), and peripheral arterial disease (OR = 6.5, 95% CI = 1.9-22.8). Despite the fact that 40% of patients underwent reoperations for diabetic foot infections and 47.3% of them required a higher level of surgery, a high rate of limb salvage could be achieved.

Clinical–Pathological Characterization of Diabetic Foot Infections

The present study has 3 aims: ( a) to characterize the clinical and pathological features of diabetic foot infections, ( b) to show the range of clinical presentations of moderate infections, and ( c) to analyze the different behavior of diabetic foot osteomyelitis regarding to its clinical presentation. A definitive diagnosis of the type of infection was made based on intraoperative findings and histopathology. Diabetic foot infections were classified into 2 types: soft tissue and bone infections. Mild infections were always superficial. Severe infections included 75% of necrotizing soft tissue infections. Moderate infections showed ample range of clinical presentations. Eighty-one patients presented osteomyelitis. Osteomyelitis was further classified as follows: osteomyelitis without ischemia and without soft tissue involvement (class 1), osteomyelitis with ischemia without soft tissue involvement (class 2), osteomyelitis with soft tissue involvement (class 3), and osteomyelitis with ischemia and soft tissue involvement (class 4). Forty-eight patients (59.3%) with osteomyelitis underwent conservative surgery, 32 (39.5%) had minor amputations including 9 open transmetatarsal amputations, and there was 1 (1.2%) major amputation. The characterization of osteomyelitis into 4 classes showed a statistically significant trend toward increased severity and increased amputation rate and mortality. In conclusion, the clinical presentation of foot infections in diabetic patients is very heterogeneous and can be classified into soft tissue infections (cellulitis, superficial and deep abscesses, and necrotizing soft tissue infections) and osteomyelitis, which was the most frequent type of infection found in the author’s series. Their division into 4 classes showed a statistically significant trend toward increased severity, amputation rate, and mortality. The diagnosis of deep soft tissue infections associated with osteomyelitis may be difficult to achieve before surgery.

Ceftobiprole: First reported experience in osteomyelitis

A 74-year-old man with long-standing diabetes presented with advanced infection of the right forefoot associated with septic arthritis and osteomyelitis involving the second and third metatarsophalangeal joints. Polymicrobial infection, which included methicillin-resistant Staphylococcus aureus, was documented. First-line antibiotic therapy, which included vancomycin, was not tolerated. A durable cure was obtained following a six-week course of intravenous ceftobiprole medocaril combined with local surgery. The present report is the first to administer intravenous ceftobiprole medocaril to a patient with methicillin-resistant S aureus-associated septic arthritis and osteomyelitis.

Methicillin-resistant Staphylococcus aureus in diabetic foot infections

Diabetic foot ulcers are often complicated by infection. Among pathogens, Staphylococcus aureus predominates. The prevalence of methicillin-resistant S. aureus (MRSA) in infected foot ulcers is 15-30% and there is an alarming trend for increase in many countries. There are also data that recognize new strains of MRSA that are resistant to vancomycin. The risk for MRSA isolation increases in the presence of osteomyelitis, nasal carriage of MRSA, prior use of antibacterials or hospitalization, larger ulcer size and longer duration of the ulcer. The need for amputation and surgical debridement increases in patients infected with MRSA. Infections of mild or moderate severity caused by community-acquired MRSA can be treated with cotrimoxazole (trimethoprim/sulfamethoxazole), doxycycline or clindamycin when susceptibility results are available, while severe community-acquired or hospital-acquired MRSA infections should be managed with glycopeptides, linezolide or daptomycin. Dalbavancin, tigecycline and ceftobiprole are newer promising antimicrobial agents active against MRSA that may also have a role in the treatment of foot infections if more data on their efficacy and safety become available.

Meticillin-resistant Staphylococcus aureus isolated from foot ulcers in diabetic patients in a Chinese care hospital: risk factors for infection and prevalence

A retrospective case–control study of 118 (male : female, 68 : 50) Chinese type 2 diabetic patients with foot ulcers (Wagner's grade 3–5) was conducted to determine the prevalence and risk factors for meticillin-resistant Staphylococcus aureus (MRSA) infection in relation to the original community or hospital parameters. Ulcer specimens were processed for Gram staining, aerobic culture and antimicrobial susceptibility testing. Staphylococcus species were tested for meticillin resistance using oxacillin. S. aureus was the most frequent pathogen (25.6 %) in diabetic patient specimens (160 isolates), and a high proportion of S. aureus isolates were MRSA (63.4 %). A high percentage of S. aureus isolates (65.4 %) satisfied the definition for hospital-associated MRSA (HA-MRSA) infection. The size of ulcers [adjusted odds ratio (OR) 1.61; 95 % confidence interval (CI) 1.22–2.12] and osteomyelitis (adjusted OR 18.51, 95 % CI 2.50–137.21) were independent predictors of MRSA infection. The HA-MRSA group had a significantly different distribution from the community-associated MRSA group with respect to age, history of diabetes and length of hospital stay (all P<0.001). Neuropathy, vascular disease (all P=0.049) and osteomyelitis (P=0.026) were the most common underlying conditions observed in the HA-MRSA group. This study contributes to the establishment of precautions against the emergence of MRSA including MRSA acquired from different sources among the Chinese population with diabetic foot ulcers based on their original or clinical parameters.

Clinical significance of the isolation of Staphylococcus epidermidis from bone biopsy in diabetic foot osteomyelitis

Introduction

Coagulase-negative staphylococci are considered as microorganisms with little virulence and usually as contaminants. In order to establish the role of Staphylococcus epidermidis as a pathogen in diabetic foot osteomyelitis, in addition to the isolation of the sole bacterium from the bone it will be necessary to demonstrate the histopathological changes caused by the infection.

Methods

A consecutive series of 222 diabetic patients with foot osteomyelitis treated surgically in the Diabetic Foot Unit at La Paloma Hospital (Las Palmas de Gran Canaria, Canary Islands, Spain) between 1 October 2002 and 31 October 2008. From the entire series including 213 bone cultures with 241 isolated organisms, we have analyzed only the 139 cases where Staphylococci were found. We analyzed several variables between the two groups: Staphylococcus aureus versus Staphylococcus epidermidis.

Results

Of the 134 patients included in this study, Staphlylococcus epidermidis was found as the sole bacterium isolated in 11 cases and accompanied by other bacteria in 12 cases. Staphlylococcus aureus was found as the sole bacterium isolated in 72 cases and accompanied by other bacteria in 39 cases. Histopathological changes were found in the cases of osteomyelitis where Staphylococcus epidermidis was the sole bacterium isolated. Acute osteomyelitis was found to a lesser extent when Staphylococcus epidermidis was the sole bacterium isolated but without significant differences with the cases where Staphylococcus aureus was the sole bacterium isolated.

Conclusion

Staphylococcus epidermidis should be considered as a real pathogen, not only a contaminant, in diabetic patients with foot osteomyelitis when the bacterium is isolated from the bone. No differences in the outcomes of surgical treatment have been found with cases which Staphlylococcus aureus was isolated.

A Randomized Controlled Trial to Examine the Efficacy and Safety of a New Super-Oxidized Solution for the Management of Wide Postsurgical Lesions of the Diabetic Foot

This randomized trial was done to test the effectiveness and safety of using a novel antiseptic solution (Dermacyn® Wound Care [DWC], Oculus Innovative Sciences, Petaluma, CA) in the management of the postoperative lesions on the infected diabetic foot. 40 patients with postsurgical lesions wider than 5 cm2 left open to heal by secondary intention were randomized into 2 groups. Group A was locally treated with DWC, whereas group B received povidone iodine as local medication, both in adjunct to systemic antibiotic therapy and surgical debridement if needed. Ischemia, renal failure, bilateral lesions, or immunodepression were considered as exclusion criteria. Patients were followed up weekly for 6 months. The primary endpoint was healing rate at 6 months, while secondary endpoints were healing time, time to achieve negative cultures, duration of antibiotic therapy, number of reinterventions, and adverse events. Healing rates at 6 months were significantly shorter in group A (90%) than in group B (55%; P < .01). The time taken for cultures to become negative and duration of antibiotic therapy were also significantly (P < .05) shorter in group A than in group B, whereas the number of reinterventions was significantly higher in group B (P < .05). No difference was noted in the adverse events except that for reinfections, which were more frequent in group B than in group A (P < .01). DWC is as safe as and more effective than standard local antiseptics in the management of wide postsurgical lesions in the infected diabetic foot.

Treatment of Diabetic Foot Osteomyelitis: A Surgical Critique

Osteomyelitis is one of the most frequent infections of the diabetic foot accounting for 10-15% of mild infections and almost 50% of severe infections. The definitive diagnosis of foot osteomyelitis requires obtaining bone samples for microbiological and histopathological studies. The treatment of osteomyelitis of the foot in diabetic patients continues to be debated. Until recently, most experts considered that the standard treatment for diabetic foot osteomyelitis should be the surgical removal of infected bone. Recent data suggest that antibiotic treatment can achieve an apparent remission of osteomyelitis though it is difficult to identify patients for this approach. One of the main arguments used to justify the solely antibiotic treatment of osteomyelitis is the alteration of foot biomechanics produced as a consequence of surgery. Conservative surgery combined with antibiotics is an attractive option in treating diabetic foot osteomyelitis because it may reduce the changes in the biomechanics of the foot and minimize the duration of antibiotic therapy. It is currently accepted that the combination of antibiotics with surgical removal of the infected bone may cure the majority of diabetic foot osteomyelitis. Recent literature emphasizes the role of antibiotics in the management of foot infections while little effort is dedicated to reviewing the surgical treatment of this challenging diabetic complication, apart from amputation. More research, including studies of adjunctive therapies in cases of bone infection in the feet of diabetic patients is required.