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

Antibiotic-eluting scaffolds with responsive dual-release kinetics facilitate bone healing and eliminate S. aureus infection

Osteomyelitis (OM) is a progressive, inflammatory infection of bone caused predominately by Staphylococcus aureus. Herein, we engineered an antibiotic-eluting collagen-hydroxyapatite scaffold capable of eliminating infection and facilitating bone healing. An iterative freeze-drying and chemical crosslinking approach was leveraged to modify antibiotic release kinetics, resulting in a layered dual-release system whereby an initial rapid release of antibiotic to clear infection was followed by a sustained controlled release to prevent reoccurrence of infection. We observed that the presence of microbial collagenase accelerated antibiotic release from the crosslinked layer of the scaffold, indicating that the material is responsive to microbial activity. As exemplar drugs, vancomycin and gentamicin-eluting scaffolds were demonstrated to be bactericidal, and supported osteogenesis in vitro. In a pilot murine model of OM, vancomycin-eluting scaffolds were observed to reduce S. aureus infection within the tibia. Finally, in a rabbit model of chronic OM, gentamicin-eluting scaffolds both facilitated radial bone defect healing and eliminated S. aureus infection. These results show that antibiotic-eluting collagen-hydroxyapatite scaffolds are a one-stage therapy for OM, which when implanted into infected bone defects simultaneously eradicate infection and facilitate bone tissue healing.

Efficacy of ceftaroline and rifampin, alone or combined, in a rat model of methicillin-resistant Staphylococcus epidermidis osteomyelitis without implant

IMPORTANCE

Methicillin-resistant Staphylococcus epidermidis (MRSE) contributes to a high percentage of orthopedic infections, and their treatment represents a huge challenge. The present study aimed to evaluate the efficacy of ceftaroline alone or combined with rifampin in a rat MRSE osteomyelitis model and the bone penetration of ceftaroline. A ceftaroline monotherapy showed a significant bacterial reduction in infected bones after a 7-day period of treatment. The combination ceftaroline plus rifampin leveraged rifampin's bactericidal activity, shortening the duration of positive culture in infected animals. These results suggest that ceftaroline and rifampin combination therapy could represent a valuable therapeutic option for human MRSE osteomyelitis and deserves further preclinical and clinical evaluation.

Calcium alginate nanoparticle crosslinked phosphorylated polyallylamine to the controlled release of clindamycin for osteomyelitis treatment

Osteomyelitis is one of the infections of the bone, and the treatment needs to the infection problems. Here, a local therapeutic approach for efficient drug delivery systems was designed to enhance the antibiotic drug's therapeutic activity. Calcium-Alginate nanoparticle (Ca-Alg) crosslinked phosphorylated polyallylamine (PPAA) was prepared through the salting-out technique, and it achieved 82.55% encapsulation of Clindamycin drug. The physicochemical characterizations of FTIR, SEM/EDX, TEM, and XRD were investigated to confirm the materials nature and formation. Clindamycin loaded Ca-Alg/PPAA system showed sustained Clindamycin release from the carrier. Cell viability was assessed in bone-related cells by Trypan blue assay and MTT assay analysis method. Both assay results exhibited better cell viability of synthesized materials against MG63 cells. MIC value of Ca-Alg/PPAA/Clindamycin in the Methicillin-resistant Staphylococcus aureus (MRSA) pathogen was 275 µg/mL, and it was 120 µg/mL for Enterobacter cloacae pathogen. The materials promising material for Osteomyelitis affected bone regeneration without any destructive effect and speedy recovery of infected parts from these investigations.

Pathogens Causing Diabetic Foot Infection and the Reliability of the Superficial Culture

Background: Diabetic foot infection (DFI) is a severe complication of diabetes and a leading cause of hospitalization in the population with diabetes. Empirical intravenous antibiotic agents are initiated according to guidelines based on previously published data on typical pathogens. Therefore, regular evaluation of the pathogens in DFI and their resistance is important to validate current therapies. We evaluated the most current data on bacterial cultures in patients treated at our hospital for DFI and the resistance to the most common antibiotic agents, as well as the reliability of superficial cultures compared with deep tissue cultures. Patients and Methods: This retrospective study was performed at the University Hospital of Tampere and comprised 325 patients with 405 hospitalizations for DFI during the years 2010-2014. Results: The most frequent pathogens in superficial and deep samples were Staphylococcus aureus (36.9%), gram-negative bacilli (24.6%), and β-hemolytic streptococci (BHS, 19.5%). Septicemia was caused most often by Staphylococcus aureus and BHS (34.6% each). The specificity of superficial culture was 91.8%-92.8% and sensitivity 66.7%-87.5%. Conclusions: This study indicates the need to cover Staphylococcus aureus, BHS, and gram-negative bacilli when treating DFI. The reliability of superficial culture was surprisingly good.

Feasibility of Percutaneous Bone Biopsy as Part of the Management of Diabetic Foot Osteomyelitis in a 100% Neuropathic, Grade 3 IDSA/IWGDF Population on an Outpatient Basis

The present study aimed to evaluate the feasibility of percutaneous bone biopsy in an ambulatory setting as part of the management of diabetic foot osteomyelitis (DFO) on an outpatient basis. DFO may complicate some cases of apparently nonsevere foot infections in patients with diabetes and greatly increase the risk of a lower extremity amputation. It has been suggested that bone culture-based antibiotic therapy is a predictive factor of success in patients with diabetes treated nonsurgically for osteomyelitis of the foot. It is recommended to identify the causative microorganism(s) by the means of either a surgical or percutaneous bone biopsy taken appropriately to select the proper antibiotic therapy. Percutaneous bone biopsy in patients not requiring surgery is, however, not performed in everyday practice as it should be according to the current recommendations. In the present retrospective study, we report a series of 23 consecutive patients with a suspicion of DFO in whom 28 bone samples were collected by percutaneous biopsy at the bedside in an outpatient setting. The percentage of positive cultures was in accordance with that reported in the literature. The mean number of isolates per specimen was 1.04. After a mean 12-month follow-up, the remission was almost of 78%. No adverse event related to the bone biopsy was noted. After a 1-year follow-up, no recurrence was recorded among the patients in remission. The results of the present study suggest that bedside percutaneous bone biopsy performed in the ambulatory setting is a valuable and safe tool in the management of DFO on an outpatient basis.

Section's osseous slice biopsy during major amputation of lower extremity: preliminary results of prospective cohort study

Background

The purpose of this cohort study was to assess the incidence of positive cultures in section’s osseous slice biopsy (SOB) taken at the level of major limb amputation. In case of positive cultures we sought whether the microorganisms present in SOB could take origin from the primary infection site necessitating the amputation. The impact of diabetes on culture results was also investigated.

Methods

This prospective cohort study, which aimed to confirm the results of the pilot study, analysed patients who underwent major limb amputation between 2012 and 2013 in three Lithuanian hospitals. SOBs at the amputation site (surgical bone biopsies) and percutaneous bone biopsies of the distal site were performed simultaneously during limb amputation. Tissue cultures were analysed by microbiologists, and species along with antibiograms were reported. Histopathological assessment and bacterial typing were also evaluated. A positive culture was defined as the identification of at least 1 bacteria not belonging to the skin flora, at least 2 bacteria belonging to the skin flora with the same antibiotic susceptibility profiles or the same bacteria belonging to the skin flora in two different sites. Fisher’s exact test and Student’s test were used to compare the populations and the microbiological results. The statistical significance level was set at P < 0.05.

Results

Sixty-nine patients (35 males/34 females), mean age 68.7 (S = 13.6) years, including 21 (30.4 %) with diabetes underwent the major limb amputation. Forty-five amputations (65.2 %) were done above the knee. In total, 207 SOBs and 207 percutaneous distal site biopsies were studied. SOB cultures were positive in 11 (15.9 %) cases. In 5 (45.5 %) cases the same microorganisms were identified in both SOB and distal biopsy cultures. No association between culture results and presence of diabetes was identified.

Conclusions

Our results suggest that, independently of the diabetes status, foot infection may silently spread along the bone and can achieve the site of major limb amputation. Additional investigations aiming to confirm this hypothesis and to evaluate a prognostic value are in progress.

In-office distal Symes lesser toe amputation: a safe, reliable, and cost-effective treatment of diabetes-related tip of toe ulcers complicated by osteomyelitis

Diabetes-related tip of lesser toe ulcers have typically been associated with both underlying hammertoe contracture and peripheral neuropathy. The combination of digital deformity and neuropathy commonly results in non-healing, deep sores that frequently become complicated by osteomyelitis. We report on a well-known, but poorly reported, technique for surgical management of non-healing tip of lesser toe ulcers. After approval by the institutional review board, a review was performed of consecutive patients who had undergone office-based distal Symes toe amputation for a non-healing tip of lesser toe ulcer from January 2007 to December 2012. A variety of clinical, laboratory, and radiographic data were collected. A total of 48 consecutive patients (48 toe ulcers) were identified for inclusion in the present study. All patients had ulcers at the time of surgery, and no patient developed repeat ulceration of the involved digit postoperatively. Of the 48 patients, 44 (92%) had hammertoe deformity preoperatively. Also, 30 patients (63%) had positive probe-to-bone results, and 29 (97%) of these patients had culture or histologic findings positive for osteomyelitis. Of the 48 patients (48 ulcers), 73% had positive bone cultures, 69% had positive pathologic findings demonstrating osteomyelitis, and 100% had clean margins. Methicillin-resistant Staphylococcus epidermidis was the most common pathogen isolated (13 of 48, 27%). No patient required additional amputation related to the operative digit. The mean follow-up period was 28.79 months. Our results have shown that in-office distal Symes lesser toe amputation is a safe, reliable, and likely cost-effective treatment of non-healing tip of lesser toe ulcers complicated by osteomyelitis. This office-based procedure allows bone biopsy diagnosis, removes the non-healing ulcer, confirms clear margins regarding the osteomyelitis, and addresses the underlying toe deformity to minimize the chances of repeat ulceration.

Evidences and Controversies About Recurrence of Diabetic Foot Osteomyelitis

Recurrence is one of the most worrying issues when dealing with diabetic foot osteomyelitis (DFO). In accordance with expert opinion in other areas of bone infection, it is accepted that very late relapse of apparently successfully treated osteomyelitis is not uncommon. However, the physiopathology of infections in large bones secondary to hematogenous osteomyelitis, infected prostheses, and open fractures is quite different from what is seen in the feet of patients with diabetes. The anatomy of the bones, the mechanism of infection and alterations in host defenses that are frequently seen in patients with diabetes may condition the onset, clinical course, and outcomes. Apparent eradication, disappearance of inflammatory signs, wound healing, bone healing based on image studies, and no recurrences during follow-up are common terms used for defining the success of therapy for DFO. Failure of initial surgical treatment, readmission to hospital, and new episodes of infection at the same or a contiguous site are considered as recurrence of osteomyelitis. Theoretically, bacteria living in the bone could be the source of clinical recurrence, but is it possible to obtain complete healing while bacteria remain alive in the bone in the feet of patients with diabetes? Can these bacteria grow and spread from the bone to the skin after years of healing? In the author’s opinion, this type of long-term recurrence of DFO has not been well documented in the medical literature. It is the aim of this illustrated guide to review the evidence and controversies regarding the recurrence of DFO.