Microbiology of diabetic foot infections: from Louis Pasteur to 'crime scene investigation'

In Vivo Biocompatibility of Electrospun Biodegradable Dual Carrier (Antibiotic + Growth Factor) in a Mouse Model-Implications for Rapid Wound Healing

Tissue engineering technologies involving growth factors have produced one of the most advanced generations of diabetic wound healing solutions. Using this approach, a nanocomposite carrier was designed using Poly(d,l-lactide-co-glycolide) (PLGA)/Gelatin polymer solutions for the simultaneous release of recombinant human epidermal growth factor (rhEGF) and gentamicin sulfate at the wound site to hasten the process of diabetic wound healing and inactivation of bacterial growth. The physicochemical characterization of the fabricated scaffolds was carried out using scanning electron microscopy (SEM) and X-ay diffraction (XRD). The scaffolds were analyzed for thermal stability using thermogravimetric analysis and differential scanning calorimetry. The porosity, biodegradability, and swelling behavior of the scaffolds was also evaluated. Encapsulation efficiency, drug loading capacity, and in vitro drug release were also investigated. Further, the bacterial inhibition percentage and detailed in vivo biocompatibility for wound healing efficiency was performed on diabetic C57BL6 mice with dorsal wounds. The scaffolds exhibited excellent wound healing and continuous proliferation of cells for 12 days. These results support the applicability of such systems in rapid healing of diabetic wounds and ulcers.

Insight into multidrug-resistant microorganisms from microbial infected diabetic foot ulcers

AIM

This study was undertaken to inspect the preponderance of multidrug-resistant (MDR) microorganisms in microbial infected diabetic foot ulcers (DFUs) in north Egypt. Moreover, their later impact on the patients and previous antibiotic therapies were taken into consideration.

METHODS

To accomplish this goal, twenty-two of diabetic foot patients with purulent wounds were enrolled in this prospective study. These wounds were swabbed and the antibiotics susceptibility patterns of most virulent bacteria and yeast were studied. Furthermore, bacterial and yeast strains were identified using 16S rRNA and 16S rRNA nucleotide sequences, respectively, and following their phenotypic characteristics employing the VITEK 2 system.

RESULTS

Microbial profiles showed a predominance of monomicrobial infections (77.3%), while polymicrobial infections were found in 22.7%. A total of 24 bacterial isolates (15 Gram-positive and 9 Gram-negative) and four yeast isolates were perceived. Four bacteria were selected based on their resistance toward more than six of empirical antibiotics. They were identified and deposited in GenBank as Acinetobacter baumanni MT3 (KY421195), Staphylococcus aureus MT1 (KY421197), Klebsiella pneumonia MT2 (KY421196), and Staphylococcus aureus MT4 (KY421198). On the other hand, one strain belonged to yeast was opted and identified as Candida albicans MT5 (MG851796).

CONCLUSION

These findings might effectively help to avert the severe complications of diabetic foot infections (DFIs) besides our endeavours to find new antimicrobial wound dressings.

A review on diabetic foot challenges in Guyanese perspective

BACKGROUND

Diabetes mellitus signifies a major public health threat worldwide. Type 2 diabetes has been reported as the fourth leading cause of death and has affected 15.5% of the adult population in Guyana, South America. Diabetes has also led to major lower extremity amputation at the only referral public hospital in Guyana. Diabetic foot and related complications are known to be multifactorial.

CONCLUSION

In this review, we highlight the information on the diabetic foot and related complications with an emphasis on Guyanese background.

Risk factors for mortality among patients undergoing major amputations due to infected diabetic feet

Background

Foot ulcers in patients with diabetes are a major public health problem and are often associated with lower limbs amputation and mortality in this population.

Objectives

To investigate the risk factors associated with mortality in patients with infected diabetic foot ulcers and major lower limb amputations.

Methods

This was an observational, retrospective, case-control study with a sample of 78 patients with infected diabetic foot ulcers who had major lower limb amputations at a Vascular Surgery Service at a university hospital.

Results

The mean age of the study sample was 63.8 ± 10.5 years, 54 (69.2%) were male, mean serum creatinine was 2.49 ± 2.4 mg/dL and mean serum hemoglobin was 7.36 ± 1.7 g/dL. There was a 47.4% rate of readmissions to the same hospital. Transtibial amputation was performed in 59.0%; and transfemoral amputation in 39.7% of the sample. In this sample, 87.2% had a positive culture, predominantly (68.0%) monomicrobial and nosocomial infection of ulcers was observed in 30.8%. The most common bacterial genera were Acinetobacter spp. (24.4%), Morganella spp. (24.4%) and Proteus spp. (23.1%). No bacterial genus was identified as a predictor of death. Creatinine level ≥ 1.3 mg/dL (OR 17.8; IC 2.1-150) and transfemoral amputation (OR 4.5; IC: 1.3-15.7) were associated with death.

Conclusions

Serum creatinine levels ≥ 1.3 mg/dL and transfemoral amputation were risk factors for death.

Prosthetic Joint Infection Trends at a Dedicated Orthopaedics Specialty Hospital

Introduction

Historically, a majority of prosthetic joint infections (PJIs) grew Gram-positive bacteria. While previous studies stratified PJI risk with specific organisms by patient comorbidities, we compared infection rates and microbiologic characteristics of PJIs by hospital setting: a dedicated orthopaedic hospital versus a general hospital serving multiple surgical specialties.

Methods

A retrospective review of prospectively collected data on 11,842 consecutive primary hip and knee arthroplasty patients was performed. Arthroplasty cases performed between April 2006 and August 2008 at the general university hospital serving multiple surgical specialties were compared to cases at a single orthopaedic specialty hospital from September 2008 to August 2016.

Results

The general university hospital PJI incidence rate was 1.43%, with 5.3% of infections from Gram-negative species. In comparison, at the dedicated orthopaedic hospital, the overall PJI incidence rate was substantially reduced to 0.75% over the 8-year timeframe. Comparing the final two years of practice at the general university facility to the most recent two years at the dedicated orthopaedics hospital, the PJI incidence was significantly reduced (1.43% vs 0.61%). Though the overall number of infections was reduced, there was a significantly higher proportion of Gram-negative infections over the 8-year timeframe at 25.3%.

Conclusion

In transitioning from a multispecialty university hospital to a dedicated orthopaedic hospital, the PJI incidence has been significantly reduced despite a greater Gram-negative proportion (25.3% versus 5.3%). These results suggest a change in the microbiologic profile of PJI when transitioning to a dedicated orthopaedic facility and that greater Gram-negative antibiotic coverage could be considered.

Platelet-rich plasma plays an antibacterial, anti-inflammatory and cell proliferation-promoting role in an in vitro model for diabetic infected wounds

Aim

This study was designed to examine the potential mechanism underlying these roles of platelet-rich plasma in treating diabetic foot ulcers (DFUs).

Methods

Staphylococcus aureus and HaCaT were co-cultured under high glucose conditions to serve as an in vitro model for infected cells in DFUs. Platelet-rich gel (PRG) or extract liquid of platelet-rich gel (EPG) were used to interfere with the model to observe the growth of HaCaT cells and S. aureus, and the effect of miR-21 changes in HaCaT cells on PDCD4, NF-κB activity and related inflammatory factors.

Results

Incubation of HaCaT cells with S. aureus promoted the decline of cell proliferation. Under this condition, the level of PDCD4 and the activity of NF-κB were increased in HaCaT cells with concomitant increased of IL-6, TNF-α and decreased IL-10, TGF-β1 in cultured supernatant. Both of PRG and EPG exhibited specific anti-S. aureus activity where they protect HaCaT cells from bacterial damage and promote cell proliferation. Meanwhile, EPG was observed to increase intracellular miRNA-21 while reduce PDCD4 expression and inhibit NF-κB activity to suppress the inflammation in HaCaT cells.

Conclusion

This in vitro model provides a valuable tool for study of wound healing in the treatment of DFUs. Our results suggest that miRNA-21 may regulate the expression of NF-κB through PDCD4 where it plays an anti-inflammatory role and promote proliferation in infected DFUs treated by PRP. These findings could provide novel therapeutic targets for refractory wounds.

Management of bacterial skin and skin structure infections with polymicrobial etiology

INTRODUCTION

Skin and Soft Tissue Infections (SSTIs) are some of the most commonly occurring bacterial infections, with a wide range of possible etiological pathogens and a considerable variety of clinical presentations and severity; from mild to severe life-threatening infections. Several classifications have been proposed based on a specific variable, such as anatomical localization, skin extension, progression rate, clinical presentation, severity, and etiological agent. Areas covered: The last criteria allows the differentiation of SSTIs as monomicrobial and polymicrobial. Among them, especially those infections with a long lasting or chronic course can be sustained by multiple microbial etiology. Most polymicrobial SSTIs can be included in the following: diabetes foot infections (DFIs), pressure ulcers infection, burn infection, and infected chronic ulcers. Expert commentary: The medical management of these infections comprises the administration of wide a spectrum antibiotic, taking into consideration the frequent occurrence of multidrug resistant microorganisms as responsible agents. An appropriate deep tissue specimen for microbiological examination is a very important issue, especially for polymicrobial infections, sometimes permitting the distinction between real pathogens and contaminants avoiding more complex antibiotic treatments. This aspect must be strongly emphasized, as frequently superficial swabs remain the specimen of choice because they are easy to obtain.

Potential bactericidal activity of S. nux-vomica-ZnO nanocomposite against multidrug-resistant bacterial pathogens and wound-healing properties

Multidrug resistance in bacterial strains has become the greatest challenge for healthcare professionals for treating non-healing ulcers such as diabetic foot infections (DFI). Plant-mediated synthesis of S. nux-vomica-ZnO nanocomposite appears as a potential new alternative therapeutic agent that might be capable of tackling antibiotic-resistant bacterial pathogens and for treating a non-healing ulcer. The aim of the study was to investigate the antibacterial potential of S. nux-vomica-ZnO nanocomposite biosynthesised from Strychnos nux-vomica against multidrug-resistant organisms (MDROs) from DFU, wound-healing properties, and cytotoxic effects. The antibacterial potential was assessed by minimum inhibitory concentration (MIC)/ minimum bactericidal concentration (MBC) assays, time-kill kinetics, protein-leakage, and flow cytometric analysis. The wound-healing properties were assessed by scratch assay on mouse L929 fibroblastic cell line to quantify cell migration towards the injured area. Cytotoxicity was assessed using 3-[4,5-dimethyl-2-thiazol-yl]-2,5-diphenyl- 2H-tetrazolium bromide (MTT) cellular viability assay on the L929 cell line and human embryonic kidney epithelial (HEK-293) cell line. Strychnos nux-vomica-ZnO nanocomposite at a size range of 10-12 nm exhibited significant bactericidal potency at a concentration of 100-200 μg/ml against MDR-Methicillin-resistant Staphylococcus aureus, MDR-Escherichia coli, MDR-Pseudomonas aeruginosa, MDR-Acinetobacter baumannii, and also against standard bacterial strains S. aureus ATCC 29213, E. coli ATCC 25922, P. aeruginosa ATCC 27853, E. faecalis ATCC 29212. S. nux-vomica-ZnO nanocomposite also exhibited wound-healing and reduced cytotoxic properties at the antimicrobially active concentrations. Our findings thus suggested remarkable bactericidal properties of S. nux-vomica-ZnO nanocomposite and can be further exploited towards for the development of an antibacterial agent against the threatening superbugs.

Resolving Digital Staphylococcal Osteomyelitis Using Bacteriophage-A Case Report

Infections involving diabetic foot ulcers (DFU) are a major public health problem and have a substantial negative impact on patient outcomes. Osteomyelitis in an ulcerated foot substantially increases the difficulty of successful treatment. While literature suggests that osteomyelitis in selected patients can sometimes be treated conservatively, with no, or minimal removal of bone, we do not yet have clear treatment guidelines and the standard treatment failure fallback remains amputation. The authors report on the successful treatment, with a long term follow up, of a 63 YO diabetic female with distal phalangeal osteomyelitis using bacteriophage, a form of treatment offering the potential for improved outcomes in this era of escalating antibiotic resistance and the increasingly recognized harms associated with antibiotic therapy.

Low Frequency of Staphylococcus Aureus in Lower Extremity Skin and Soft Tissue Infections

BACKGROUND

Staphylococcus aureus is often implicated in skin/soft tissue infections (SSTI). However, SSTI at sites of pressure necrosis and peripheral vascular disease (PVD) are often polymicrobial. The frequency of S aureus in these infections is uncertain.

METHODS

We retrospectively reviewed culture results from adults (January 1, 2015-March 31, 2017), evaluated their records and selected SSTI in lower extremities. The patient demographics, comorbidities, characteristics and culture results were recorded. The results were stratified by S aureus status and a composite risk score (RS) was developed (2 points for each difference in S aureus frequency with P < 0.05 [chi-square test] and 1 point for P = 0.06-0.1). The predictors of S aureus were determined by regression analysis using SSPS software.

RESULTS

We encountered 356 lower extremity-SSTI (243 foot/ankle, 56 tibia/calf, 30 thigh, 12 hip and 15 groin). S aureus was detected in 173 (48.6%) cases, 59.6% were methicillin-resistant isolates. S aureus was more common in lesions without necrosis (56.3% vs. 42.9%; P = 0.01), with drainage (59.6% vs. 44.7%; P = 0.02), in male sex (53.2% vs. 40.0%; P = 0.02) and was less common in patients with PVD (38.1% vs. 50.9%; P = 0.07), and paraplegia (39.6% vs. 50.0%; P = 0.2). S aureus was less common in polymicrobial SSTI (45.0% vs. 58.5%; P = 0.03). RS of 0-8 correlated with increasing S aureus prevalence from 23.1% (RS = 0-1) to 78.6% (RS = 8; P<0.001). The predictors of S aureus were drainage (odds ratio [OR] = 1.83; 95% confidence intervals [CI]: 1.11, 3.02), lack of PVD (OR = 1.59; CI: 1.03, 2.46) and absence of necrosis (OR = 1.91; CI: 1.08, 3.40).

CONCLUSIONS

Patients with suspected polymicrobial lower extremity-SSTI and low RS may not need empirical antistaphylococcal therapy.

Applications of Bacteriophages in the Treatment of Localized Infections in Humans

In the recent years, multidrug-resistant bacteria have become a global threat, and phage therapy may to be used as an alternative to antibiotics or, at least, as a supplementary approach to treatment of some bacterial infections. Here, we describe the results of bacteriophage application in clinical practice for the treatment of localized infections in wounds, burns, and trophic ulcers, including diabetic foot ulcers. This mini-review includes data from various studies available in English, as well as serial case reports published in Russian scientific literature (with, at least, abstracts accessible in English). Since, it would be impossible to describe all historical Russian publications; we focused on publications included clear data on dosage and rout of phage administration.

Concordance in diabetic foot ulceration: a cross-sectional study of agreement between wound swabbing and tissue sampling in infected ulcers

BACKGROUND

There is inadequate evidence to advise clinicians on the relative merits of swabbing versus tissue sampling of infected diabetic foot ulcers (DFUs).

OBJECTIVES

To determine (1) concordance between culture results from wound swabs and tissue samples from the same ulcer; (2) whether or not differences in bacterial profiles from swabs and tissue samples are clinically relevant; (3) concordance between results from conventional culture versus polymerase chain reaction (PCR); and (4) prognosis for patients with an infected DFU at 12 months' follow-up.

METHODS

This was a cross-sectional, multicentre study involving patients with diabetes and a foot ulcer that was deemed to be infected by their clinician. Microbiology specimens for culture were taken contemporaneously by swab and by tissue sampling from the same wound. In a substudy, specimens were also processed by PCR. A virtual 'blinded' clinical review compared the appropriateness of patients' initial antibiotic regimens based on the results of swab and tissue specimens. Patients' case notes were reviewed at 12 months to assess prognosis.

RESULTS

The main study recruited 400 patients, with 247 patients in the clinical review. There were 12 patients in the PCR study and 299 patients in the prognosis study. Patients' median age was 63 years (range 26-99 years), their diabetes duration was 15 years (range 2 weeks-57 years), and their index ulcer duration was 1.8 months (range 3 days-12 years). Half of the ulcers were neuropathic and the remainder were ischaemic/neuroischaemic. Tissue results reported more than one pathogen in significantly more specimens than swabs {86.1% vs. 70.1% of patients, 15.9% difference [95% confidence interval (CI) 11.8% to 20.1%], McNemar's p-value < 0.0001}. The two sampling techniques reported a difference in the identity of pathogens for 58% of patients. The number of pathogens differed in 50.4% of patients. In the clinical review study, clinicians agreed on the need for a change in therapy for 73.3% of patients (considering swab and tissue results separately), but significantly more tissue than swab samples required a change in therapy. Compared with traditional culture, the PCR technique reported additional pathogens for both swab and tissue samples in six (50%) patients and reported the same pathogens in four (33.3%) patients and different pathogens in two (16.7%) patients. The estimated healing rate was 44.5% (95% CI 38.9% to 50.1%). At 12 months post sampling, 45 (15.1%) patients had died, 52 (17.4%) patients had a lower-extremity ipsilateral amputation and 18 (6.0%) patients had revascularisation surgery.

LIMITATIONS

We did not investigate the potential impact of microbiological information on care. We cannot determine if the improved information yield from tissue sampling is attributable to sample collection, sample handling, processing or reporting.

CONCLUSIONS

Tissue sampling reported both more pathogens and more organisms overall than swabbing. Both techniques missed some organisms, with tissue sampling missing fewer than swabbing. Results from tissue sampling more frequently led to a (virtual) recommended change in therapy. Long-term prognosis for patients with an infected foot ulcer was poor.

FUTURE WORK

Research is needed to determine the effect of sampling/processing techniques on clinical outcomes and antibiotic stewardship.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Antibiotic Susceptibility Profiles of Bacteria from Diabetic Foot Infections in Selected Teaching Hospitals in Southwestern Nigeria

One of the serious complications associated with diabetes is foot ulcer and this condition affects the quality of life in patients in all classes, races and ages. Chronic wounds are prone to colonization by wide array of microorganisms which could be extremely hazardous to patients if effective and timely therapeutic intervention is not made. This study was conducted to determine the antibiotic susceptibility profiles of bacteria from diabetic foot infections in southwestern Nigeria. Samples were collected from a total of 142 diabetic foot ulcer patients with moistened sterile cotton swabs. Nutrient agar, Mac-Conkey agar, blood agar and mannitol salt agar media were used for the isolation of total viable bacteria, Gram-negative non-spore forming lactose fermenters, fastidious bacteria and staphylococci, respectively. Morphological and biochemical characteristics of pure cultures were determined in accordance with standard laboratory criteria. API 20 E and API 20 NE were used for the confirmation of identity of the bacterial isolates. The disc diffusion technique was employed for the determination of antibiotic susceptibility of bacterial isolates in accordance with standard procedures. The antibiotics investigated included amikacin, amoxicillin, ampicillin, ceftazidime, cefazolin, ceftriaxone, chloramphenicol, ciprofloxacin, clindamycin, gentamicin, imipenem, linezolid, methicillin, netilmicin, ofloxacin, oxacillin, penicillin, piperacilin, sulfamethoxazole, trimethoprim and vancomycin. One hundred and seventy-seven isolates were encountered and these were characterized into eleven bacterial species. These included Staphylococcus aureus (22.03%), Pseudomonas aeruginosa (16.95%), Staphylococcus epidermidis (12.43%), Proteus mirabilis (8.48%), Klebsiella pneumoniae (7.91%), E. coli (7.35%), Staphylococcus saprophyticus (6.78%), Streptococcus pyogenes (5.65%), Morganella morganii (5.09%), Citrobacter freundii (4.52%) and Acinetobacter baumannii (2.83%). Gram-negative bacteria showed 76.99% susceptibility to the antibiotics while 22.85% was resistant. Gram-positive bacteria showed 93.75% susceptibility and 5.01% resistance to the antibiotics. This study revealed that there is no definite aetiologic bacterial agent for diabetic foot infections and many of the associated bacteria are sensitive to certain antibiotics.

Enhanced antibacterial effects of green synthesized ZnO NPs using Aristolochia indica against Multi-drug resistant bacterial pathogens from Diabetic Foot Ulcer

BACKGROUND

Increased incidence of Multi-drug resistance in microorganisms has become the greatest challenge in the treatment of Diabetic Foot Ulcer (DFU) and urges the need of a new antimicrobial agent. In this study, we determined the bactericidal effects of ZnO nanoparticles (ZnO NPs) green synthesized from Aristolochia indica against Multi-drug Resistant Organisms (MDROs) isolated from pus samples of DFU patients attending in a tertiary care hospital in South India.

METHODS

ZnO NPs were characterized by UV-vis-DRS spectroscopy, Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) and for its zeta potential value. MIC/MBC assays were performed to determine bactericidal or bacteriostatic effects. Time-kill assays, Protein leakage and Flow cytometric analysis evaluated bacterial cell death at 1x MIC and 2x MIC concentrations of ZnO NPs.

RESULTS

ZnO NPs of size 22.5nm with a zeta potential of -21.9±1mV exhibited remarkable bactericidal activity with MIC/MBC ranging from 25 to 400μg/ml with a significant reduction in viable count from 2h onwards. Protein leakage and Flow cytometric analysis confirmed bacterial cell death due to ZnO NPs.

CONCLUSION

This study concluded that green synthesis protocol offers reliable, eco-friendly approach towards the development of antimicrobial ZnO NPs to combat antibiotic drug resistance.

In vivo diabetic wound healing with nanofibrous scaffolds modified with gentamicin and recombinant human epidermal growth factor

Diabetic wounds are susceptible to microbial infection. The treatment of these wounds requires a higher payload of growth factors. With this in mind, the strategy for this study was to utilize a novel payload comprising of Eudragit RL/RS 100 nanofibers carrying the bacterial inhibitor gentamicin sulfate (GS) in concert with recombinant human epidermal growth factor (rhEGF); an accelerator of wound healing. GS containing Eudragit was electrospun to yield nanofiber scaffolds, which were further modified by covalent immobilization of rhEGF to their surface. This novel fabricated nanoscaffold was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The thermal behavior of the nanoscaffold was determined using thermogravimetric analysis and differential scanning calorimetry. In the in vitro antibacterial assays, the nanoscaffolds exhibited comparable antibacterial activity to pure gentemicin powder. In vivo work using female C57/BL6 mice, the nanoscaffolds induced faster wound healing activity in dorsal wounds compared to the control. The paradigm in this study presents a robust in vivo model to enhance the applicability of drug delivery systems in wound healing applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 641-651, 2018.

Risk Factors for Infection with Pseudomonas aeruginosa in Diabetic Foot Infections

BACKGROUND

Selecting empirical therapy for a diabetic foot infection (DFI) requires knowing how likely infection with Pseudomonas aeruginosa is in a particular patient. We designed this study to define the risk factors associated with P aeruginosa in DFI.

METHODS

We performed a preplanned microbiological subanalysis of data from a study assessing the effects of treatment with intralesional epidermal growth factor for diabetic foot wounds in patients in Turkey between January 1, 2012, and December 31, 2013. Patients were screened for risk factors, and the data of enrolled individuals were recorded in custom-designed patient data forms. Factors affecting P aeruginosa isolation were evaluated by univariate and multivariate logistic regression analyses, with statistical significance set at P < .05.

RESULTS

There were 174 patients enrolled in the main study. Statistical analysis was performed in 90 evaluable patients for whom we had microbiological assessments. Cultures were sterile in 19 patients, and 89 bacterial isolates were found in the other 71. The most frequently isolated bacteria were P aeruginosa (n = 23, 25.8%) and Staphylococcus aureus (n = 12, 13.5%). Previous lower-extremity amputation and a history of using active wound dressings were the only statistically significant independent risk factors for the isolation of P aeruginosa in these DFIs.

CONCLUSIONS

This retrospective study provides some information on risk factors for infection with this difficult pathogen in patients with DFI. We need prospective studies in various parts of the world to better define this issue.

Direct Gram staining and its various benefits in the diagnosis of bacterial infections

In the era of rapid development of molecular and other diagnostic methods, direct Gram staining (DGS) tends to remain in the background, although it can provide both microbiologists and clinicians numerous benefits. The aim of this review was to emphasize the importance of DGS for the diagnosis of many clinically important infections. A PubMed search was carried out using relevant keywords for articles published primarily since 2010. The DGS can provide early information for a timely diagnosis of infections, can reveal the causative agents of the infections even under suboptimal conditions of specimen collection, transport or identification methods, can detect the presence of rare/unusual pathogens, moreover, the method shows the specimen quality, by distinguishing between contamination and true infection, it can direct or change initial antibiotic treatment before the availability of culture results, can indicate the need of other methods for pathogen identification and, in some cases, can show the need for emergency attention such as urgent antibiotic therapy and surgical measures. Briefly, the DGS remains an easy, rapid, inexpensive and important method, which use should be encouraged in conditions of a standardized and controlled performance to avoid technical or interpretation errors.

Microbiota of Chronic Diabetic Wounds: Ecology, Impact, and Potential for Innovative Treatment Strategies

World Health Organization considered diabetes as one of the 20th century epidemics, estimating that over 10% of the world population is diabetic or at high risk. Self-assessment studies indicate that diabetic patients consider chronic wounds to affect their quality of life more dramatically than vision loss or renal failure. In addition to being the main reason for diabetic patients' hospitalization, the economic burden of diabetic chronic wounds is close to 1% of United Kingdom and United States health systems budgets, which exceeds the funds allocated to the treatment of some types of cancer in both countries. Among the factors preceding the emergence of chronic diabetic wounds, also designated diabetic foot ulcers (DFUs), hygiene and pressure in specific areas are under patient control, while others are still far from being understood. A triple impairment in the innervation, immune responses, and vascularization associated to DFU has been extensively studied by the scientific community. However, the skin natural microbiota has only recently emerged as having a tremendous impact on DFU emergence and evolution to chronicity. Despite the great inter- and intra-variability of microbial colonizers, ongoing efforts are now focused on deciphering the impact of commensal and pathogenic microbiota on DFU etiology, as well as the mechanisms of interkingdom microbial-host communication. This review summarizes recent work in this context and offers new microbiological perspectives that may hold potential in the prevention and treatment of chronic diabetic wounds.

Skin and Soft Tissue Infections

The skin is colonized by a diverse collection of microorganisms which, for the most part, peacefully coexist with their hosts. Skin and soft tissue infections (SSTIs) encompass a variety of conditions; in immunocompromised hosts, SSTIs can be caused by diverse microorganisms-most commonly bacteria, but also fungi, viruses, mycobacteria, and protozoa. The diagnosis of SSTIs is difficult because they may commonly masquerade as other clinical syndromes or can be a manifestation of systemic disease. In immunocompromised hosts, SSTI poses a major diagnostic challenge, and clinical dermatological assessment should be initially performed; to better identify the pathogen and to lead to appropriate treatment, etiology should include cultures of lesions and blood, biopsy with histology, specific microbiological analysis with special stains, molecular techniques, and antigen-detection methodologies. Here, we reviewed the epidemiology, pathophysiology, clinical presentation, and diagnostic techniques, including molecular biological techniques, used for SSTIs, with a focus on the immunocompromised host, such as patients with cellular immunodeficiency, HIV, and diabetic foot infection.

Can molecular DNA-based techniques unravel the truth about diabetic foot infections?

Diabetes foot infections are a common condition and a major causal pathway to lower extremity amputation. Identification of causative pathogens is vital in directing antimicrobial therapy. Historically, clinicians have relied upon culture-dependent techniques that are now acknowledged as both being selective for microorganisms that thrive under the physiological and nutritional constraints of the microbiology laboratory and that grossly underestimate the microbial diversity of a sample. The amplification and sequence analysis of the 16S rRNA gene has revealed a diversity of microorganisms in diabetes foot infections, extending the view of the diabetic foot microbiome. The interpretation of these findings and their relevance to clinical care remains largely unexplored. The advent of molecular methods that are culture-independent and employ massively parallel DNA sequencing technology represents a potential 'game changer'. Metagenomics and its shotgun approach to surveying all DNA within a sample (whole genome sequencing) affords the possibility to characterize not only the microbial diversity within a diabetes foot infection (i.e. 'which microorganisms are present') but the biological functions of the community such as virulence and pathogenicity (i.e. 'what are the microorganisms capable of doing'), moving the focus from single species as pathogens to groups of species. This review will examine the new molecular techniques for exploration of the microbiome of infected and uninfected diabetic foot ulcers, exploring the potential of these new technologies and postulating how they could translate to improved clinical care. Copyright © 2016 John Wiley & Sons, Ltd.

Bacterial Profile and Antibiotic Resistance in Patients with Diabetic Foot Ulcer in Guangzhou, Southern China: Focus on the Differences among Different Wagner's Grades, IDSA/IWGDF Grades, and Ulcer Types

OBJECTIVE

To understand the bacterial profile and antibiotic resistance patterns in diabetic foot infection (DFI) in different Wagner's grades, IDSA/IWGDF grades, and different ulcer types in Guangzhou, in order to provide more detailed suggestion to the clinician about the empirical antibiotic choice.

METHODS

207 bacteria were collected from 117 DFIs in Sun Yat-sen Memorial Hospital from Jan.1, 2010, to Dec.31, 2015. The clinical data and microbial information were analyzed.

RESULTS

The proportion of Gram-negative bacteria (GNB) was higher than Gram-positive bacteria (GPB) (54.1% versus 45.9%), in which Enterobacteriaceae (73.2%) and Staphylococcus (65.2%) were predominant, respectively. With an increasing of Wagner's grades and IDSA/IWGDF grades, the proportion of GNB bacterial infection, especially Pseudomonas, was increased. Neuro-ischemic ulcer (N-IFU) was more susceptible to GNB infection. Furthermore, with the aggravation of the wound and infection, the antibiotic resistance rates were obviously increased. GPB isolated in ischemic foot ulcer (IFU) showed more resistance than the N-IFU, while GNB isolates were on the opposite.

CONCLUSIONS

Different bacterial profiles and antibiotic sensitivity were found in different DFU grades and types. Clinician should try to stay updated in antibiotic resistance pattern of common pathogens in their area. This paper provided them the detailed information in this region.

Comparing the Effectiveness of Polymer Debriding Devices Using a Porcine Wound Biofilm Model

Objective: Debridement to remove necrotic and/or infected tissue and promote active healing remains a cornerstone of contemporary chronic wound management. While there has been a recent shift toward less invasive polymer-based debriding devices, their efficacy requires rigorous evaluation.

Approach: This study was designed to directly compare monofilament debriding devices to traditional gauze using a wounded porcine skin biofilm model with standardized application parameters. Biofilm removal was determined using a surface viability assay, bacterial counts, histological assessment, and scanning electron microscopy (SEM).

Results: Quantitative analysis revealed that monofilament debriding devices outperformed the standard gauze, resulting in up to 100-fold greater reduction in bacterial counts. Interestingly, histological and morphological analyses suggested that debridement not only removed bacteria, but also differentially disrupted the bacterially-derived extracellular polymeric substance. Finally, SEM of post-debridement monofilaments showed structural changes in attached bacteria, implying a negative impact on viability.

Innovation: This is the first study to combine controlled and defined debridement application with a biologically relevant ex vivo biofilm model to directly compare monofilament debriding devices.

Conclusion: These data support the use of monofilament debriding devices for the removal of established wound biofilms and suggest variable efficacy towards biofilms composed of different species of bacteria.

Diabetes mellitus and the skin

Diabetes is a debilitating, life-threatening disease accounting in 2015 for the death of 5 million people worldwide. According to new estimations, 415 million adults currently suffer from the disease, and this number is expected to rise to 642 million by 2040. High glucose blood levels also affect the skin among systemic organs, and skin disorders can often predict the onset of this metabolic disorder. In this review, we address the pathomechanistic effects of diabetes on the skin and give an overview on the most common skin diseases associated with diabetes.

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.

Susceptibility patterns of Staphylococcus aureus biofilms in diabetic foot infections

BACKGROUND

Foot infections are a major cause of morbidity in people with diabetes and the most common cause of diabetes-related hospitalization and lower extremity amputation. Staphylococcus aureus is by far the most frequent species isolated from these infections. In particular, methicillin-resistant S. aureus (MRSA) has emerged as a major clinical and epidemiological problem in hospitals. MRSA strains have the ability to be resistant to most β-lactam antibiotics, but also to a wide range of other antimicrobials, making infections difficult to manage and very costly to treat. To date, there are two fifth-generation cephalosporins generally efficacious against MRSA, ceftaroline and ceftobripole, sharing a similar spectrum. Biofilm formation is one of the most important virulence traits of S. aureus. Biofilm growth plays an important role during infection by providing defence against several antagonistic mechanisms. In this study, we analysed the antimicrobial susceptibility patterns of biofilm-producing S. aureus strains isolated from diabetic foot infections. The antibiotic minimum inhibitory concentration (MIC) was determined for ten antimicrobial compounds, along with the minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC), followed by PCR identification of genetic determinants of biofilm production and antimicrobial resistance.

RESULTS

Results demonstrate that very high concentrations of the most used antibiotics in treating diabetic foot infections (DFI) are required to inhibit S. aureus biofilms in vitro, which may explain why monotherapy with these agents frequently fails to eradicate biofilm infections. In fact, biofilms were resistant to antibiotics at concentrations 10-1000 times greater than the ones required to kill free-living or planktonic cells. The only antibiotics able to inhibit biofilm eradication on 50 % of isolates were ceftaroline and gentamicin.

CONCLUSIONS

The results suggest that the antibiotic susceptibility patterns cannot be applied to biofilm established infections. Selection of antimicrobial therapy is a critical step in DFI and should aim at overcoming biofilm disease in order to optimize the outcomes of this complex pathology.

Molecular typing, virulence traits and antimicrobial resistance of diabetic foot staphylococci

BACKGROUND

Diabetes mellitus is a major chronic disease that continues to increase significantly. One of the most important and costly complications of diabetes are foot infections that may be colonized by pathogenic and antimicrobial resistant bacteria, harboring several virulence factors, that could impair its successful treatment. Staphylococcus aureus is one of the most prevalent isolate in diabetic foot infections, together with aerobes and anaerobes.

METHODS

In this study, conducted in the Lisbon area, staphylococci isolated (n = 53) from diabetic foot ulcers were identified, genotyped and screened for virulence and antimicrobial resistance traits. Genetic relationship amongst isolates was evaluated by pulsed-field-gel-electrophoresis with further multilocus sequence typing of the identified pulsotypes. PCR was applied for detection of 12 virulence genes and e-test technique was performed to determine minimal inhibitory concentration of ten antibiotics.

RESULTS

Among the 53 isolates included in this study, 41 Staphylococcus aureus were identified. Staphylococcal isolates were positive for intercellular adhesins icaA and icaD, negative for biofilm associated protein bap and pantone-valentine leucocidin pvl. S. aureus quorum sensing genes agrI and agrII were identified and only one isolate was positive for toxic shock syndrome toxin tst. 36 % of staphylococci tested were multiresistant and higher rates of resistance were obtained for ciprofloxacin and erythromycin. Clonality analysis revealed high genomic diversity and numerous S. aureus sequence types, both community- and hospital-acquired, belonging mostly to clonal complexes CC5 and C22, widely diffused in Portugal nowadays.

CONCLUSIONS

This study shows that diabetic foot ulcer staphylococci are genomically diverse, present resistance to medically important antibiotics and harbour virulence determinants. These properties suggest staphylococci can contribute to persistence and severity of these infections, leading to treatment failure and to the possibility of transmitting these features to other microorganisms sharing the same niche. In this context, diabetic patients may become a transmission vehicle for microorganisms' clones between community and clinical environments.

Isolation and Genetic Analysis of Multidrug Resistant Bacteria from Diabetic Foot Ulcers

Severe diabetic foot ulcers (DFUs) patients visiting Sir Sunderlal Hospital, Banaras Hindu University, Varanasi, were selected for this study. Bacteria were isolated from swab and deep tissue of 42 patients, for examining their prevalence and antibiotic sensitivity. DFUs of majority of the patients were found infected with Enterococcus spp. (47.61%), Escherichia coli (35.71%), Staphylococcus spp. (33.33%), Alcaligenes spp. (30.95%), Pseudomonas spp. (30.95%), and Stenotrophomonas spp. (30.95%). Antibiotic susceptibility assay of 142 bacteria with 16 antibiotics belonging to eight classes showed the presence of 38 (26.76%) isolates with multidrug resistance (MDR) phenotypes. MDR character appeared to be governed by integrons as class 1 integrons were detected in 26 (68.42%) isolates. Altogether six different arrays of genes (aadA1, aadB, aadAV, dhfrV, dhfrXII, and dhfrXVII) were found within class 1 integron. Gene cassette dhfrAXVII-aadAV (1.6 kb) was present in 12 (3 Gram positive and 9 Gram negative) isolates and was conserved across all the isolates as evident from RFLP analysis. In addition to the presence of class 1 integron, six β-lactamase resistance encoding genes namely bla TEM, bla SHV, bla OXA, bla CTX-M-gp1, bla CTX-M-gp2, and bla CTX-M-gp9 and two methicillin resistance genes namely mecA and femA and vancomycin resistance encoding genes (vanA and vanB) were identified in different isolates. Majority of the MDR isolates were positive for bla TEM (89.47%), bla OXA (52.63%), and bla CTX-M-gp1 (34.21%). To our knowledge, this is the first report of molecular characterization of antibiotic resistance in bacteria isolated from DFUs from North India. In conclusion, findings of this study suggest that class-1 integrons and β-lactamase genes contributed to the MDR in above bacteria.

The diabetic foot in 2015: an overview

In 2015, it can be said that the diabetic foot is no longer the Cinderella of diabetic complications. Thirty years ago there was little evidence-based research taking place on the diabetic foot, and there were no international meetings addressing this topic. Since then, the biennial Malvern Diabetic Foot meetings started in 1986, the American Diabetes Association founded their Foot Council in 1987, and the European Association for the Study of Diabetes established a Foot Study Group in 1998. The first International Symposium on the Diabetic Foot in The Netherlands was convened in 1991, and this was soon followed by the establishment of the International Working Group on the Diabetic Foot that has produced useful guidelines in several areas of investigation and the management of diabetic foot problems. There has been an exponential rise in publications on diabetic foot problems in high impact factor journals, and a comprehensive evidence-base now exists for many areas of treatment. Despite the extensive evidence available, it, unfortunately, remains difficult to demonstrate that most types of education are efficient in reducing the incidence of foot ulcers. However, there is evidence that education as part of a multi-disciplinary approach to diabetic foot ulceration plays a pivotal role in incidence reduction. With respect to treatment, strong evidence exists that offloading is the best modality for healing plantar neuropathic foot ulcers, and there is also evidence from two randomized controlled trials to support the use of negative-pressure wound therapy in complex post-surgical diabetic foot wounds. Hyperbaric oxygen therapy exhibits the same evidence level and strength of recommendation. International guidelines exist on the management of infection in the diabetic foot. Many randomized trials have been performed, and these have shown that the agents studied generally produced comparable results, with the exception of one study in which tigecycline was shown to be clinically inferior to ertapenem ± vancomycin. Similarly, there are numerous types of wound dressings that might be used in treatment and which have shown efficacy, but no single type (or brand) has shown superiority over others. Peripheral artery disease is another major contributory factor in the development of ulceration, and its presence is a strong predictor of non-healing and amputation. Despite the proliferation of endovascular procedures in addition to open revascularization, many patients continue to suffer from severely impaired perfusion and exhaust all treatment options. Finally, the question of the true aetiopathogenesis of Charcot neuroarthropathy remains enigmatic, although much work is currently being undertaken in this area. In this area, it is most important to remember that a clinically uninfected, warm, insensate foot in a diabetic patient should be considered as a Charcot foot until proven otherwise, and, as such, treated with offloading, preferably in a cast.

Managing infection: a holistic approach

All wound infection presents risks for the patient, but the risks are multiplied in the presence of a comorbidity such as diabetes, when they can potentially be fatal. Where diabetic foot ulcer (DFU) infection is concerned, early recognition is crucial. Prompt treatment, comprising wound cleansing, debridement of devitalised tissue and use of antimicrobial dressings, can stop locally infected ulcers from deteriorating further.

The role of anaerobes in diabetic foot infections

Diabetic foot infections (DFI) are a common cause of morbidity and, on occasion, even mortality. Infection can be either mono- or polymicrobial, with a wide variety of potential pathogens. Anaerobes may be involved, particularly in wounds that are deeper or more chronic, and are more frequently identified when using modern molecular techniques, such as 16s PCR and pyrosequencing. It remains unclear whether the presence of anaerobes in DFI leads to more severe manifestations, or if these organisms are largely colonizers associated with the presence of greater degrees of tissue ischemia and necrosis. Commonly used empiric antibiotic therapy for diabetic foot infections is generally broad-spectrum and usually has activity against the most frequently identified anaerobes, such as Peptostreptococcus and Bacteroides species. Adequate surgical debridement and, when needed, foot revascularization may be at least as important as the choice of antibiotic to achieve a successful treatment outcome.