Merlin Guggenheim

Changes in bacterial isolates from burn wounds and their antibiograms: a 20-year study (1986-2005).

BACKGROUND Our aim is to elucidate shifts in the bacterial spectrum colonising burn wounds and corresponding antibiotic susceptibilities during a 20-year study period. METHODS Microbiological results from burn patients collected between 1986 and 2005 were analysed retrospectively. RESULTS Staphylococcus aureus was isolated most frequently (20.8%), followed by Escherichia coli (13.9%), Pseudomonas aeruginosa (11.8%), coagulase-negative staphylococci (CNS) (10.9%), Enterococcus sp. (9.7%), Enterobacter cloacae (5.6%), Klebsiella pneumoniae (5%), Acinetobacter sp. (3.2%), Proteus mirabilis (2%) and Stenotrophomonas maltophilia (1.4%). Susceptibility of S. aureus to broad-spectrum substances such as ciprofloxacin or penicillinase-stable penicillins has waned, others such as cotrimoxazole or netilmicin remained effective. Not a single resistance against vancomycin was recorded. Increases in methicillin-resistant S. aureus (MRSA) were pronounced (3% in 1986-1997 (the first of the three study periods) to 16% in 1998-2001 and 13% in 2002-2005). Results for methicillin-resistant CNS (MRCNS) show an even greater increase. P. aeruginosa has shown increasing susceptibility against netilmicin (1986-1989: 84%, 2002-2005: 95%). Susceptibility of P. aeruginosa to ceftazidime has decreased markedly. S. maltophilia has shown clinically relevant susceptibility mainly against ciprofloxacin. Acinetobacter sp. have shown little susceptibility to most antibiotics. Imipenem or meropenem have been very reliable reserve antibiotics throughout the study period for the fermenting Enterobacteriaceae (E. coli, K. pneumoniae, E. cloacae and P. mirabilis), with susceptibilities of or near 100%. CONCLUSION In-depth knowledge of the bacteria causing infectious complications and of their antibiotic susceptibilities is a prerequisite for treating burn patients. Our study shows shifts in the microbial spectrum and their antibiogram, which mandate frequent reassessments.

Spider silk fibres in artificial nerve constructs promote peripheral nerve regeneration

Abstract.  Objective: In our study, we describe the use of spider silk fibres as a new material in nerve tissue engineering, in a 20‐mm sciatic nerve defect in rats. Materials and methods: We compared isogenic nerve grafts to vein grafts with spider silk fibres, either alone or supplemented with Schwann cells, or Schwann cells and matrigel. Controls, consisting of veins and matrigel, were transplanted. After 6 months, regeneration was evaluated for clinical outcome, as well as for histological and morphometrical performance. Results: Nerve regeneration was achieved with isogenic nerve grafts as well as with all constructs, but not in the control group. Effective regeneration by isogenic nerve grafts and grafts containing spider silk was corroborated by diminished degeneration of the gastrocnemius muscle and by good histological evaluation results. Nerves stained for S‐100 and neurofilament indicated existence of Schwann cells and axonal re‐growth. Axons were aligned regularly and had a healthy appearance on ultrastructural examination. Interestingly, in contrast to recently published studies, we found that bridging an extensive gap by cell‐free constructs based on vein and spider silk was highly effective in nerve regeneration. Conclusion: We conclude that spider silk is a viable guiding material for Schwann cell migration and proliferation as well as for axonal re‐growth in a long‐distance model for peripheral nerve regeneration.

Morbidity and recurrence after completion lymph node dissection following sentinel lymph node biopsy in cutaneous malignant melanoma.

Objective:To assess the nature and rates of complications and recurrences after completion lymph node dissection (CLND) following positive sentinel lymph node biopsy (SLNB) in melanoma patients. Summary Background Data:In contrast to SLNB, CLND is associated with considerable morbidity. CLND delays nodal recurrence, thereby prolonging disease-free survival (DFS), but not overall melanoma-specific survival. Elaborate studies on morbidity and recurrence rates after CLND are scarce. Therefore, many controversies concerning extent and nature of CLND exist. Methods:We conducted a retrospective study on 100 melanoma patients, on whom we performed CLND between October 1999 and December 2005. The median observation period was 38.8 months. Results:We performed a total of 102 CLNDs, [46.1% axillary (47/102), 42.2% groin (43/102), 11.8% neck (12/102)]. Groin dissection (GD) and axillary dissection (AD) led to comparable morbidity (47.6% and 46.8%), but complications were more severe in GD, mandating additional surgery in 25.6% (11/43), versus 8.5% (4/47) in AD. Of the GD patients, 18.5% (8/43) were readmitted for complications compared with 10.4% (5/47) of AD patients. Only 8.3% (1/12) of ND patients suffered complications, mandating neither readmittance nor further surgery. During the median observation period, 65 (65%) of these patients showed DFS, and 35 (35%) exhibited recurrences after a median DFS of 12.5 months. Of the recurrences, 31.4% were nodal, 42.9% distant, and 25.7% local/in-transit. Of our AD patients, 28.3% suffered recurrences (13/46), as did 33.3% of the GD (14/42) and 66.7% of the ND patients (8/12). Conclusions:CLND is fraught with considerable morbidity. Local control of the dissected nodal basins was achieved with a modified radical approach in ADs (levels I + II only) and, to a lesser extent, GDs, but not in NDs. Clinical trials are necessary to establish guidelines on the extent of lymphatic dissection.

Application of the Zürich biofilm model to problems of cariology.

The term biofilm is increasingly replacing ‘plaque’ in the literature, but concepts and existing paradigms are changing much more slowly. There is little doubt that biofilm research will lead to more realistic perception and interpretation of the physiology and pathogenicity of microorganisms colonizing plaques in the oral cavity. There is clear evidence that the genotypic and phenotypic expression profiles of biofilm and planktonic bacteria are different. Several techniques are available today to study multispecies biofilms of oral bacteria, each having its particular advantages and weaknesses. We describe a biofilm model developed in Zürich and demonstrate a number of applications with direct or indirect impact on prophylactic dentistry: spatial arrangement and associative behavior of various species in biofilms; multiplex fluorescent in situ hybridization analysis of oral bacteria in biofilms; use of the biofilm model to predict in vivo efficacy of antimicrobials reliably; mass transport in biofilms; de- and remineralization of enamel exposed to biofilms in vitro. The potential of biofilm experimentation in oral biology has certainly not yet been fully exploited and dozens of possible interesting applications could be investigated. The overall physiological parameters of multispecies biofilms can be measured quite accurately, but it is still impossible to assess in toto the multitude of interactions taking place in such complex systems. What can and should be done is to test hypotheses stemming from experiments with planktonic cells in monospecies cultures. In particular, it will be interesting to investigate the relevance to biofilm composition and metabolism of specific gene products by using appropriate bacterial mutants.

Spider silk constructs enhance axonal regeneration and remyelination in long nerve defects in sheep.

Background Surgical reapposition of peripheral nerve results in some axonal regeneration and functional recovery, but the clinical outcome in long distance nerve defects is disappointing and research continues to utilize further interventional approaches to optimize functional recovery. We describe the use of nerve constructs consisting of decellularized vein grafts filled with spider silk fibers as a guiding material to bridge a 6.0 cm tibial nerve defect in adult sheep. Methodology/Principal Findings The nerve constructs were compared to autologous nerve grafts. Regeneration was evaluated for clinical, electrophysiological and histological outcome. Electrophysiological recordings were obtained at 6 months and 10 months post surgery in each group. Ten months later, the nerves were removed and prepared for immunostaining, electrophysiological and electron microscopy. Immunostaining for sodium channel (NaV 1.6) was used to define nodes of Ranvier on regenerated axons in combination with anti-S100 and neurofilament. Anti-S100 was used to identify Schwann cells. Axons regenerated through the constructs and were myelinated indicating migration of Schwann cells into the constructs. Nodes of Ranvier between myelin segments were observed and identified by intense sodium channel (NaV 1.6) staining on the regenerated axons. There was no significant difference in electrophysiological results between control autologous experimental and construct implantation indicating that our construct are an effective alternative to autologous nerve transplantation. Conclusions/Significance This study demonstrates that spider silk enhances Schwann cell migration, axonal regrowth and remyelination including electrophysiological recovery in a long-distance peripheral nerve gap model resulting in functional recovery. This improvement in nerve regeneration could have significant clinical implications for reconstructive nerve surgery.

The influence of sentinel lymph node tumour burden on additional lymph node involvement and disease-free survival in cutaneous melanoma--a retrospective analysis of 392 cases.

Twenty per cent of sentinel lymph node (SLN)-positive melanoma patients have positive non-SLN lymph nodes in completion lymph node dissection (CLND). We investigated SLN tumour load, non-sentinel positivity and disease-free survival (DFS) to assess whether certain patients could be spared CLND. Sentinel lymph node biopsy was performed on 392 patients between 1999 and 2005. Median observation period was 38.8 months. Sentinel lymph node tumour load did not predict non-SLN positivity: 30.8% of patients with SLN macrometastases (⩾2 mm) and 16.4% with micrometastases (⩽2 mm) had non-SLN positivity (P=0.09). Tumour recurrences after positive SLNs were more than twice as frequent for SLN macrometastases (51.3%) than for micrometastases (24.6%) (P=0.005). For patients with SLN micrometastases, the DFS analysis was worse (P=0.003) when comparing those with positive non-SLNs (60% recurrences) to those without (17.6% recurrences). This difference did not translate into significant differences in DFS: patients with SLN micrometastasis, either with (P=0.022) or without additional positive non-SLNs (P<0.0001), fared worse than patients with tumour-free SLNs. The 2-mm cutoff for SLN tumour load accurately predicts differences in DFS. Non-SLN positivity in CLND, however, cannot be predicted. Therefore, contrary to other studies, no recommendations concerning discontinuation of CLND based on SLN tumour load can be deduced.

30 years later—Does the ABSI need revision?

In light of changes in patient demographics together with constant developments in burn care, the predictive accuracy of the Abbreviated Burns Severity Index (ABSI) - first described in 1982 - for estimating the mortality of present day burns patients, may be questionable. We reviewed the records of 2813 burns patients treated between January 1968 and December 2008 in the intensive care unit at our institution, aiming to identify emerging discrepancies between the estimated and calculated outcome, based on each of the ABSI variables and the total burn score. The predictive value of each of the defined ABSI variables was confirmed to be highly significant. Univariable and multivariable analysis revealed an exponential increase in odds ratio (OR) for mortality for patients older than 60 years and more than 30% TBSA burned and showed OR values over 10 times higher than other significant variables like inhalation injury. Nevertheless, the ABSI for the estimation of mortality in our entire patient collective was highly accurate and could not be optimised by adapting the point distribution to the increase in OR. Our data indicates that despite significant changes in patient demographics and medical advances over the past 30 years, the ABSI scoring system is still an accurate and valuable tool in the prediction of burn patient mortality.

A case-matched controlled study on high-voltage electrical injuries vs thermal burns.

The aim of this study was to provide an increased level of evidence on surgical management of high-tension electrical injuries compared with thermal burns using a case-controlled study design. Sixty-eight patients (64 males, 4 females, aged 33.7 ± 13 years) with high-tension electrical burns were matched for age, gender, and burnt extent with a cohort of patients sustaining thermal burns. Data were analyzed for cause of accident (occupational vs nonoccupational), concomitant injuries, extent of burn and burn depth, surgical management, complications, and hospital stay. High-tension electrical burn patients required an average of 5.2 ± 4 operations (range, 1-23 operations) compared with 3.3 ± 1.9 (range, 1-10 operations) after thermal burns (P = .0019). Amputation rates (19.7% vs 1.5%), escharotomy/fasciotomy rates (47% vs 21%), and total hospitalization days (44 d vs 32 d) were significantly higher in high-tension electrical injuries (P < .05). Creatinine kinase levels were significantly elevated during the first 2 days in patients with subsequent amputations. Free flap failure was observed during the first 4 weeks after the trauma, whereas no flap failure occurred at later stages. Local, pedicled, and distant flaps were used in 15% of the patients. The mortality in both groups was 13.2% vs 11%, respectively (nonsignificant). High-voltage electrical injury remains a complex surgical challenge. When performing free flap coverage, caution must be taken for a vulnerable phase lasting up to 4 weeks after the trauma. This phase is likely the result of a progressive intima lesion, potentially hazardous to microvascular reconstruction. The use of pedicle flaps may resemble an alternative to free flaps during this period.

Interactions between Spider Silk and Cells – NIH/3T3 Fibroblasts Seeded on Miniature Weaving Frames

Background Several materials have been used for tissue engineering purposes, since the ideal matrix depends on the desired tissue. Silk biomaterials have come to focus due to their great mechanical properties. As untreated silkworm silk has been found to be quite immunogenic, an alternative could be spider silk. Not only does it own unique mechanical properties, its biocompatibility has been shown already in vivo. In our study, we used native spider dragline silk which is known as the strongest fibre in nature. Methodology/Principal Findings Steel frames were originally designed and manufactured and woven with spider silk, harvesting dragline silk directly out of the animal. After sterilization, scaffolds were seeded with fibroblasts to analyse cell proliferation and adhesion. Analysis of cell morphology and actin filament alignment clearly revealed adherence. Proliferation was measured by cell count as well as determination of relative fluorescence each after 1, 2, 3, and 5 days. Cell counts for native spider silk were also compared with those for trypsin-digested spider silk. Spider silk specimens displayed less proliferation than collagen- and fibronectin-coated cover slips, enzymatic treatment reduced adhesion and proliferation rates tendentially though not significantly. Nevertheless, proliferation could be proven with high significance (p<0.01). Conclusion/Significance Native spider silk does not require any modification to its application as a biomaterial that can rival any artificial material in terms of cell growth promoting properties. We could show adhesion mechanics on intracellular level. Additionally, proliferation kinetics were higher than in enzymatically digested controls, indicating that spider silk does not require modification. Recent findings concerning reduction of cell proliferation after exposure could not be met. As biotechnological production of the hierarchical composition of native spider silk fibres is still a challenge, our study has a pioneer role in researching cellular mechanics on native spider silk fibres.

Lower limb revascularisation preceding surgical wound coverage – An interdisciplinary algorithm for chronic wound closure

BACKGROUND Chronic wounds may occur or persist due to arterial insufficiency. Despite the high prevalence of arterial occlusive disease, a search of the literature has yielded a paucity of data on the benefit of interventions to recanalise lower extremity arteries prior to surgical closure of chronic wounds. OBJECTIVE To investigate the correlation of simple clinical examinations and apparative diagnostics for the detection of arterial occlusive disease of the lower extremity in patients with chronic wounds, and to evaluate the benefit of vascular procedures to optimise wound perfusion before surgical closure. PATIENTS AND METHODS During a 6-year period, 150 patients with chronic lower extremity wounds (no healing for more than 30 days) were included into this prospective study. All patients underwent palpation of foot pulses, Doppler sonography and measurement of occlusive pressures. Positive clinical findings were re-evaluated by angiography. All patients with peripheral extremity vessel occlusions underwent vascular interventions (percutaneous transluminal angioplasty with stenting, open thrombectomy or vascular bypass surgery) prior to surgical wound closure. RESULTS In all 34 patients (21%) with missing foot pulses, suspicious Doppler signals or pathological occlusive pressure measurements, the clinical diagnosis of arterial occlusion was confirmed by angiography. An arterial pathology had previously been diagnosed in merely two of those patients. Nineteen patients underwent percutaneous transluminal angioplasty and 21 stents were implanted; in 10 cases, open thrombectomy or vascular bypasses were performed. In all 34 patients, sufficient peripheral recanalisation and improved wound perfusion were successfully achieved. For definitive wound closure, microsurgical tissue transplantation was performed in 15 patients. Angiography was performed prior to surgery. In 11 patients, regional or local flaps were used. Six patients received split skin grafting only; two wounds healed conservatively following vascular intervention. Vacuum-assisted closure (VAC) therapy was applied in 15 cases. Postoperatively, three cases of impaired wound healing and one infection occurred. CONCLUSIONS Arterial insufficiency can be diagnosed safely by simple clinical examination. All clinically pathological results were successfully confirmed by angiography, allowing for a targeted peripheral vessel reopening to improve wound perfusion before surgery. This straightforward algorithm helped to improve the success of surgical therapy of chronic lower extremity wounds.