Diagnostic value of the CD 15 focus score in two-stage revision arthroplasty of periprosthetic joint infections : High specificity in diagnosing infect eradication.

INTRODUCTION: The purpose of this study is to use the CD15 focus score (FS) to determine the sensitivity and specificity of bacterial infection persistence in spacer-based two-stage revision arthroplasty. METHODS: The analysis comprises 112 cases that were subjected to revision due to the presence of infection upon replacement of a joint endoprosthesis. The histopathological data were collected in accordance with the synovial-like interface membrane (SLIM) classification and the CD15-FS and correlated with the microbiological data (MD). The quantifying evaluation of the CD15-FS was performed without knowledge regarding the microbiological data (MD). Correlation with the MD was performed after a 14-day cultivation period. RESULTS: With a single evaluation (1 focus, field area: 1.2 mm2) with a score value of 42, the CD15-FS showed a sensitivity for the eradication of infections of 0.64 and a specificity of 0.79 (PPV = 0.5; NPV = 0.87). With tenfold evaluation (10 foci, field area: 12 mm2) with a score value of 220, the sensitivity for the eradication was 0.68, the specificity 0.91 (PPV = 0.7; NPV = 0.89). No statistically significant correlation between the score values and the different infectious species could be detected. Based on the MD in 112 cases the rate of infection eradication was 75%. Polymethylmethacrylate-particles (PMMA) were detected in the perispacertissue in 64 cases (58%). No significant correlation could be established between microbiological pathogen detection and the presence of PMMA. CONCLUSION: In all cases (n = 112), periimplant synovial tissue (SLIM) with variable fibroblastic cellularity, capillary proliferation, leukocytic infiltration, fibrin deposition, new formation of woven bone and detection of PMMA particles was observed. These cases were classified as type IX perispacer synovialis/SLIM: type IX­A with histopathological infection eradication and type IX­B with histopathological infection persistence.

Acceptable mid- to long-term survival rates and functional outcomes following a single design rotating hinge total knee arthroplasty.

PURPOSE: This study first analyzes implant survival of this single design modular rotating hinge knee and identifies potential risk factors for failure and evaluates joint function using the postoperative WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) score, active flexion and extension deficit. METHODS: 131 prostheses implanted for failure of prior total knee arthroplasty (n = 120) or complex primary procedures (n = 11) using a single modular implant (MUTARS-modular universal tumor and revision system GenuX, Implantcast, Buxtehude, Germany) between 2006 and 2014 including 73 patients treated for periprosthetic joint infection with a two-stage revision protocol were retrospectively identified. Implant survival was assessed using the Kaplan-Meier method; potential risk factors were identified using the log-rank test, as well as non-parametric analysis. Postoperative function was assessed using the WOMAC and measurement of range of motion. RESULTS: After a median follow-up of 62 months, 37 implants required implant revision (28%). Five-year survival was 69.7% [95% CI (confidence interval) 60.9-78.5] with periprosthetic (re-) infection being the main cause for failure (15%), followed by aseptic loosening (9%). In cases of periprosthetic infection, infection-free survival was 83% at 5 years (95% CI 74-92) with twelve patients suffering reinfection (16%).While body mass index (p = 0.75), age (p = 0.16) or indication for rotating hinge knee arthroplasty (p = 0.25) had no influence on survival, Charlson comorbidity score (CCI) (p = 0.07) and number of previous revision surgeries (p = 0.05) correlated with implant failure. There was trend (p = 0.1) for improved survival in fully cemented implants. Mean postoperative WOMAC was 127(range 55-191), 11 patients (15%) had limited knee extension. CONCLUSIONS: Rotating hinge total knee arthroplasty using a single modular implant shows acceptable survival rates and function compared to previous studies with (re-)infection being the most relevant mode of failure. Patients with a high CCI and multiple previous surgeries are at increased risk for failure. LEVEL OF EVIDENCE: Retrospective cohort study, III.

Biocide-Tolerant Listeria monocytogenes Isolates from German Food Production Plants Do Not Show Cross-Resistance to Clinically Relevant Antibiotics.

Contamination of food during processing is recognized as a main transmission route of Listeria monocytogenes To prevent microbial contamination, biocides are widely applied as disinfectants in food processing plants. However, there are concerns about the development of antimicrobial resistance in foodborne pathogens due to widespread biocide usage. In our study, 93 L. monocytogenes isolates from German food production facilities were (i) tested for biocide and antibiotic susceptibility using broth microdilution assays, (ii) analyzed for links between reduced biocide susceptibility and antibiotic resistance, and (iii) characterized by whole-genome sequencing, including the detection of genes coding for biocide tolerance, antibiotic resistance, and other virulence factors. Fifteen L. monocytogenes isolates were tolerant to benzalkonium chloride (BAC), and genes conferring BAC tolerance were found in 13 of them. Antibiotic resistance was not associated with biocide tolerance. BAC-tolerant isolates were assigned to 6 multilocus sequence type (MLST) clonal complexes, and most of them harbored internalin A pseudogenes with premature stop codons or deletions (n = 9). Our study demonstrated a high genetic diversity among the investigated isolates including genotypes that are frequently involved in human infections. Although in vitro adaptation studies to biocides have raised concerns about increasing cross-resistance to antibiotics, our results do not provide evidence for this phenomenon in field isolates.IMPORTANCE Foodborne pathogens such as L. monocytogenes can persist in food production environments for a long time, causing perennial outbreaks. Hence, bacterial pathogens are able to survive cleaning and disinfection procedures. Accordingly, they may be repeatedly exposed to sublethal concentrations of disinfectants, which might result in bacterial adaptation to these biocides. Furthermore, antibiotic coresistance and cross-resistance are known to evolve under biocide selection pressure in vitro Hence, antimicrobial tolerance seems to play a crucial role in the resilience and persistence of foodborne pathogens in the food chain and might reduce therapeutic options in infectious diseases.

What is the Likelihood That Tumor Endoprostheses Will Experience a Second Complication After First Revision in Patients With Primary Malignant Bone Tumors And What Are Potential Risk Factors?

BACKGROUND: Endoprosthetic reconstruction of massive bone defects has become the reconstruction method of choice after limb-sparing resection of primary malignant tumors of the long bones. Given the improved survival rates of patients with extremity bone sarcomas, an increasing number of patients survive but have prosthetic complications over time. Several studies have reported on the outcome of first endoprosthetic complications. However, no comprehensive data, to our knowledge, are available on the likelihood of an additional complication and the associated risk factors, despite the impact of this issue on the affected patients. QUESTIONS/PURPOSES: (1) What are the types and timing of complications and the implant survivorship free from revision after the first complication? (2) Does survivorship free from repeat revision for a second complication differ by anatomic sites? (3) Is the type of first complication associated with the risk or the type of a second complication? (4) Are patient-, tumor-, and treatment-related factors associated with a higher likelihood of repeat revision? METHODS: Between 1993 and 2015, 817 patients underwent megaprosthetic reconstruction after resection of a tumor in the long bones with a single design of a megaprosthetic system. No other prosthetic system was used during the study period. Of those, 75% (616 of 817) had a bone sarcoma. Seventeen patients (3%) had a follow-up of less than 6 months, 4.5% (27 of 599) died with the implant intact before 6 months and 43% (260 of 599 patients) underwent revision. Forty-three percent of patients (260 of 599) experienced a first prosthetic complication during the follow-up period. Ten percent of patients (26 of 260) underwent amputation after the first complication and were excluded from further analysis. Second complications were classified using the classification of Henderson et al. to categorize surgical results. Briefly, this system categorizes complications as wound dehiscence (Type 1); aseptic loosening (Type 2); implant fractures or breakage and periprosthetic fracture (Type 3); infection (Type 4); and tumor progression (Type 5). Implant survival curves were calculated with the Kaplan-Meier method and compared using the log-rank test. Hazard ratios (HR) were estimated with their respective 95% CIs in multivariate Cox regression models. RESULTS: A second complication occurred in 49% of patients (115 of 234) after a median of 17 months (interquartile range [IQR] 5 to 48) after the surgery for the first complication. The time to complication did not differ between the first (median 16 months; IQR 5 to 57) and second complication (median 17 months; IQR 5 to 48; p = 0.976). The implant survivorship free from revision surgery for a second complication was 69% (95% CI 63 to 76) at 2 years and 46% (95% CI 38 to 53) at 5 years. The most common mode of second complication was infection 39% (45 of 115), followed by structural complications with 35% (40 of 115). Total bone and total knee reconstructions had a reduced survivorship free from revision surgery for a second complication at 5 years (HR 2.072 [95% CI 1.066 to 3.856]; p = 0.031) compared with single joint replacements. With the numbers we had, we could not show a difference between the survivorship free of revision for a second complication based on the type of the first complication (HR 0.74 [95% CI 0.215 to 2.546]; p = 0.535). We did not detect an association between total reconstruction length, patient BMI, and patient age and survivorship free from revision for a second complication. Patients had a higher risk of second complications after postoperative radiotherapy (HR 1.849 [95% CI 1.092 to 3.132]; p = 0.022) but not after preoperative radiotherapy (HR 1.174 [95% CI 0.505 to 2.728]; p = 0.709). Patients with diabetes at the time of initial surgery had a reduced survivorship free from revision for a second complication (HR 4.868 [95% CI 1.497 to 15.823]; p = 0.009). CONCLUSIONS: Patients who undergo revision to treat a first megaprosthetic complication must be counseled regarding the high risk of future complications. With second complications occurring relatively soon after the first revision, regular orthopaedic follow-up visits are advised. Preoperative rather than postoperative radiotherapy should be performed when possible. Future studies should evaluate the effectiveness of different approaches in treating complications considering implant survivorship free of revision for a second complication. LEVEL OF EVIDENCE: Level III, therapeutic study.

Genetic and phenotypic analysis of Vibrio cholerae non-O1, non-O139 isolated from German and Austrian patients.

Vibrio cholerae belonging to the non-O1, non-O139 serogroups are present in the coastal waters of Germany and in some German and Austrian lakes. These bacteria can cause gastroenteritis and extraintestinal infections, and are transmitted through contaminated food and water. However, non-O1, non-O139 V. cholerae infections are rare in Germany. We studied 18 strains from German and Austrian patients with diarrhea or local infections for their virulence-associated genotype and phenotype to assess their potential for infectivity in anticipation of possible climatic changes that could enhance the transmission of these pathogens. The strains were examined for the presence of genes encoding cholera toxin and toxin-coregulated pilus (TCP), as well as other virulence-associated factors or markers, including hemolysins, repeats-in-toxin (RTX) toxins, Vibrio seventh pandemic islands VSP-1 and VSP-2, and the type III secretion system (TTSS). Phenotypic assays for hemolysin activity, serum resistance, and biofilm formation were also performed. A dendrogram generated by incorporating the results of these analyses revealed genetic differences of the strains correlating with their clinical origin. Non-O1, non-O139 strains from diarrheal patients possessed the TTSS and/or the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin, which were not found in the strains from ear or wound infections. Routine matrix-assisted laser desorption/ionization (MALDI-TOF) mass spectrometry (MS) analysis of all strains provided reliable identification of the species but failed to differentiate between strains or clusters. The results of this study indicate the need for continued surveillance of V. cholerae non-O1, non-O139 in Germany, in view of the predicted increase in the prevalence of Vibrio spp. due to the rise in surface water temperatures.

[Bone defect reconstruction in bone sarcoma surgery: tumour endoprosthesis versus biological reconstruction]. / Rekonstruktion knöcherner Defekte in der Knochensarkomchirurgie: Tumorendoprothese vs. biologische Rekonstruktion.

BACKGROUND: Primary bone sarcomas typically arise in the long bones and the pelvis of children and adolescence but may also occur in adults. Meta/diaphysial tumour involvement resulting in the necessity of a joint replacement is more common than diaphysial tumour sites. AIM: In the treatment of these tumours, both endoprosthetic replacement and biological reconstruction techniques are used. Each technique has method-specific advantages and disadvantages. RESULTS: To choose the appropriate surgical method, a multitude of influencing parameters need to be considered. The age at treatment (soft tissue situation/estimated growth/biological potential of the bone), therapeutic concept (palliative vs. curative), the tumour site (upper/lower extremity), tumour expansion (diaphysis/metaphysis) and oncological treatment concept (chemotherapy/radiotherapy) are key factors significantly influencing the surgical technique in terms of functional outcome and longevity of the reconstruction. CONCLUSION: Surgical treatment of bone sarcoma requires broad-based experience of the oncological surgeon. Knowledge of the different surgical technics and reconstruction methods is decisive to offer the individual patient the best oncological and functional outcome.

[Management of complications in megaprostheses]. / Komplikationsmanagement bei Megaprothesen.

BACKGROUND: Megaprostheses are frequently used after segmental resection of bone sarcomas, bone metastases, and in large osseous defects in revision arthroplasty. OBJECTIVES: The incidence of the most common complications associated the use of megaprostheses are reported. The management of complications including therapeutic recommendations are described. MATERIALS AND METHODS: The current knowledge and our own experience of complication management with the use of megaprostheses are presented. RESULTS: Prospective, randomized studies or meta-analyses on this topic are lacking. An analysis of the literature shows that beside the occurrence of a local recurrence, periprosthetic infection remains the most serious complication. Two-stage revision remains the gold standard, but a single-stage exchange of the prosthesis without removing the stems might be possible in selected cases. Infection is associated with a higher risk of secondary amputation. In contrast, mechanical failures (e.g., wear of the bushings in knee replacements and aseptic loosening of the stems) can be treated more easily. Dislocation of a proximal femur replacement can mostly be prevented by using bi- or tripolar cups. CONCLUSIONS: Complications with the use of megaprostheses can be successfully treated by revision surgery in most cases.

[Histopathological diagnostics of arthrofibrosis]. / Histopathologische Diagnostik der Arthrofibrose.

Joint surgery is one of the most important and successful disciplines in surgery; nevertheless, complications still occur, especially in total knee arthroplasty and surgery of the anterior cruciate ligament. A significant disease in this context is arthrofibrosis. This review article presents the cellular and molecular pathogenetic concept of arthrofibrosis, the spectrum of histopathological diagnostics and differential diagnostics and a classification into joint endoprosthesis-associated and non-joint endoprosthesis-associated arthrofibrosis is proposed. The basis of the histopathological diagnostics is the standardized tissue removal with subsequent fixation in formalin. In the case of joint implant failure and the problem of endoprosthesis-associated arthrofibrosis, the histopathological diagnostics can be carried out according to the consensus classification of synovia-like interface membrane (SLIM). Arthrofibrosis is characterized by fibrosis, a high fibroblast cellularity with immunohistochemical detection of cytoplasmic beta catenin expression. The presence of endoprosthesis-associated arthrofibrosis is probable above a threshold of 20 beta catenin positive fibroblasts per high-power field (HPF). The diagnosis of a non-endoprosthesis-associated arthrofibrosis can be classified according to the joint pathology algorithm. Diffuse non-endoprosthesis-associated arthrofibrosis is characterized by generalized proliferation of connective tissue in the whole joint and localized circumscribed arthrofibrosis is characterized by a nodose cyclops-like fibrosis. The clarification of the cause of arthrofibrosis is based on an interdisciplinary cooperation. In addition to the histopathological diagnostics, this includes clinical, surgical, biomechanical, arthroscopic, microbiological, laboratory parameter and radiological findings.

Characterization of a Yersinia enterocolitica biotype 1A strain harbouring an ail gene.

AIMS: The chromosomal ail gene (attachment and invasion locus) is commonly used as target gene for the detection of pathogenic Y. enterocolitica strains in food testing. The ail PCR does not detect strains of biotype 1A (BT1A), which are regarded as non-pathogenic because BT1A strains lack the virulence plasmid and chromosomally encoded virulence genes. In some recent reports, however, BT1A strains were discovered that harboured the ail gene. We isolated an ail-positive strain and characterized this strain with phenotypic and genotypic methods to study its possible relation to pathogenic Y. enterocolitica strains. METHODS AND RESULTS: The ail region of the BT1A strain was sequenced and compared with the corresponding region of nonpathogenic BT1A strains and pathogenic strains. Pulsed field gel electrophoresis (PFGE) analysis was applied revealing no similarity of the PFGE pattern of this strain to the patterns of pathogenic strains. Virulence-gene-based PCR analyses showed the strain to be positive for ystB, but negative for virulence genes ystA, virF and yadA. Whole-cell MALDI-TOF MS combined with a shrinkage discriminant analysis approach was applied and clearly classified the ail-positive biotype 1A strain within the cluster of BT1A strains. CONCLUSIONS: PCR detection of ail sequences in food matrices should be followed by the isolation of the responsible strain and its characterization using phenotypic or genotypic methods. SIGNIFICANCE AND IMPACT OF THE STUDY: The ail gene may be present in Y. enterocolitica BT1A strains, which are commonly considered as nonpathogenic. Efficient methods such as PCR typing of other virulence genes or rapid MALDI-TOF MS-based bacterial profiling allow a more comprehensive assessment of the pathogenicity potential of Yersinia strains.

5-(4-Hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-7-phenyl-2,3,6,7-tetrahydro-1,4-thiazepines as compounds with high affinity at the benzodiazepine binding site on GABA(A) receptors.

A series of thiazepines has been studied as new ligands for the benzodiazepine binding site of the GABAA receptor. Compounds with high affinity and weak selectivity regarding alpha beta3gamma2, alpha2beta3gamma2, alpha3beta3gamma2, and alpha5beta3gamma2 subtypes were found. The pharmacophore is discussed based on experimental and theoretical results. The thiazepine sulfur atom was found to be able to act as hydrogen bond acceptor.

[Vibrio infections from food and sea water. Introducing the "VibrioNet"]. / Vibrio-Infektionen durch Lebensmittel und Meerwasser. Das Netzwerk "VibrioNet" stellt sich vor.

Vibrio is a genus of bacteria present in surface and coastal waters as well as in marine organisms worldwide. In many countries, pathogenic Vibrio species are a main cause of bacterial diarrhea, which may result from comsumption of contaminated seafood and fish products or from drinking contaminated water. Vibrio infections may also gain in importance in our regions due to global warming and the increase in the world trade of seafood. The research network "VibrioNet" studies pathogenic Vibrios in the marine environment and in seafood consumed by humans as a potential, new emerging zoonotic agent. An assessment of the risk arising from pathogenic non-cholera-vibrios in central Europe is the target of a multidisciplinary research effort. The research network will be strengthened by cooperations with international partners from countries in which Vibrio infections play a major role (Bangladesh, Chile, India, Thailand, and Vietnam).

Rapid identification and characterization of Vibrio species using whole-cell MALDI-TOF mass spectrometry.

AIMS: Vibrio identification by means of traditional microbiological methods is time consuming because of the many biochemical tests that have to be performed to distinguish closely related species. This work aimed at evaluating the use of MALDI-TOF mass spectrometry for the rapid identification of Vibrio (V.) spp. as an advantageous application to rapidly discriminate the most important Vibrio spp. and distinguish Vibrio spp. from closely related bacterial species like Photobacterium damselae and Grimontia hollisae and other aquatic bacteria like Aeromonas spp. METHODS AND RESULTS: Starting from sub-colony amounts of pure cultures grown on agar plates, a very simple sample preparation procedure was established and combined with a rapid and automated measurement protocol that allowed species identification within minutes. Closely related species like Vibrio alginolyticus and Vibrio parahaemolyticus or Vibrio cholerae and Vibrio mimicus could thus be differentiated by defining signatures of species-identifying biomarker ions (SIBIs). As a reference method for species designation and for determination of relationships between strains with molecular markers, partial rpoB gene sequencing was applied. CONCLUSIONS: The MALDI-TOF MS-based method as well as the rpoB sequence-based approach for Vibrio identification described in this study produced comparable classification results. The construction of phylogenetic trees from MALDI-TOF MS and rpoB sequences revealed a very good congruence of both methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results suggest that whole-cell MALDI-TOF MS-based proteometric characterization represents a powerful tool for rapid and accurate classification and identification of Vibrio spp. and related species.

Fungal prosthetic joint infection in total hip or knee arthroplasty: a retrospective single-centre study of 26 cases.

AIMS: Fungal prosthetic joint infections (PJIs) are rare and account for about 1% of total PJIs. Our aim was to present clinical and microbiological results in treating these patients with a two-stage approach and antifungal spacers. PATIENTS AND METHODS: We retrospectively reviewed our institutional database and identified 26 patients with positive fungal cultures and positive Musculoskeletal Infection Society (MSIS) criteria for PJI who were treated between 2009 and 2017. We identified 18 patients with total hip arthroplasty (THA) and eight patients with total knee arthroplasty (TKA). The surgical and antifungal treatment, clinical and demographic patient data, complications, relapses, and survival were recorded and analyzed. RESULTS: The median follow-up was 33 months. The success rate was 38.5% (10/26). Fluconazole resistance was found in 15%. Bacterial co-infection was common in 44% of patients for THA and 66% of patients with TKA. Mortality, reoperations, and treatment failure were common complications. CONCLUSION: Treatment with a two-stage exchange is a possible option for treatment, although fungal infections have a high failure rate. Therapeutic factors for treatment success remain unclear. Cite this article: Bone Joint J 2019;101-B:589-595.

First description of an Anaerobiospirillum succiniciproducens prosthetic joint infection.

Anaerobiospirillum succiniciproducens belongs to the normal flora of cats and dogs and can rarely infect humans. Here, we report the first case of an A. succiniciproducens prosthetic joint infection.

Relationship between activating and editing functions of the adenylation domain of apo-tyrocidin synthetase 1 (apo-TY1).

Tyrocidine synthetase 1 (TY1), the initial monomodular constituent of the tyrocidine biosynthetic system, exhibits relaxed substrate specificity, however an efficient editing of the mis-activated amino acid provides for fidelity of product formation. We chose to analyse the consequence of single amino acid substitutions, in the amino acid activation site of apo-TY1, on the editing functions of the enzyme. Discrimination between L-Phe and D-Phe by apo-TY1 depends primarily on the editing reaction. Distraction of unnatural amino acid substrates, such as L-PheSer, implies that editing is not designated to select a specific mis-activated amino acid, but instead to discriminate all mis-activated amino acid analogues. It was shown that active site residues which interact with the adenylate are essential for both activation and editing. Substitution of Lys186 with arginine substantially reduces the editing capacity of the protein. Loss of amino acid discrimination ability by the apo-K186T and apo-R416T mutant proteins suggests a role of active site residues in maintaining the structural determinants for substrate selection. Inadequate conformational changes, induced by non-cognate amino acid substrates, promote ATP breakdown yielding P(i) and ADP. Replacement of residue Lys186 or Arg416 enhances ATP hydrolysis implying a role in binding or adjusting of the triphosphate chain for adenylate formation and pyrophosphate cleavage.

Synthesis of (di)adenosine polyphosphates by non-ribosomal peptide synthetases (NRPS).

In response to nutritional stress conditions, Bacillus brevis produces the cyclodecapeptide antibiotic tyrocidine via tyrocidine synthetase, a multifunctional non-ribosomal peptide synthetase. The apo-form of tyrocidine synthetase 1 forms adenosine (5')tetraphospho(5')adenosine, when incubated with MgATP(2-), amino acid and inorganic pyrophosphatase. The synthesis is an intrinsic property of the adenylation domain, is strictly dependent upon the amino acid, and proceeds from a reverse reaction of adenylate formation involving a second ATP molecule. In the presence of tri- or tetrapolyphosphate preferential synthesis of adenosine 5'-tetraphosphate and adenosine 5'-pentaphosphate occurs, respectively. A potential involvement of adenosine (5')-n-phospho(5')adenosine in the regulation of the biosynthetic process has been suggested.

Probing the domain structure and ligand-induced conformational changes by limited proteolysis of tyrocidine synthetase 1.

The boundaries of the structural domains in peptide synthetases and the conformational changes related to catalysis were investigated by limited proteolysis of tyrocidine synthetase 1 (TY1). Four regions sensitive to proteolysis were detected (cleavage site at Arg13, Arg424, Arg509 and Arg602) that, in addition to an N-terminal extension, accurately delineate the domain boundaries of the adenylate-forming domain, the aminoacyl carrier domain, and the epimerisation domain. Limited proteolysis of an active N-terminal truncated deletion mutant, His6DeltaTY1, generated two stable and structurally independent subunits, corresponding to the subdomains of the adenylation domain. The structural integrity of the carrier domain was substantiated by its resistance to proteolytic degradation. Evidence is provided that the C-terminal "spacer" region with epimerising and/or condensing activity folds into an autonomous domain stable against degradation by limited proteoly sis. In the presence of substrates, reduced susceptibility to proteolysis was observed in the linker region connecting the subdomains of the adenylation domain, and corresponding to a peptide stretch of low electron density in the X-ray structure of the homologous firefly luciferase. Sequence analysis has shown that the respective linker contains conserved residues, whereas the linker regions connecting the structural domains are of low homology with a significant content of Pro, Ala, Glu and polar residues. A combination of kinetic and proteolytic studies using ATP analogues with substitutions in the phosphate chain, AMP-PcP, AMP-PNP and AMP-cPP, strongly suggests that the generation of a productive complex is associated with the ability of the beta, gamma-pyrophosphate moiety of ATP to adopt the proper active-site conformation. These data substantiate the observation that peptide synthetases undergo a series of conformational changes in the process of adenylate formation and product release.

The nonribosomal code.

How genes are expressed and translated into proteins (using mRNA, codons and tRNAs as adaptor molecules) forms the basis of the 'genetic code'. Many peptides are synthesized nonribosomally, however, by large protein complexes that also serve as templates. Recent advances have shed light on what the nonribosomal code is and how it can be read.

Interleukin-6 in two-stage revision arthroplasty: what is the threshold value to exclude persistent infection before re-implanatation?

The purpose of this study was to evaluate whether the serum level of interleukin 6 (IL-6) could be used to identify the persistence of infection after the first stage of a two-stage revision for periprosthetic joint infection. Between 2010 and 2011, we prospectively studied 55 patients (23 men, 32 women; mean age 69.5 years; 36 to 86) with a periprosthetic joint infection. Bacteria were identified in two intra-operative tissue samples during re-implantation in 16 patients. These cases were classified as representing persistent infection. To calculate a precise cut-off value which could be used in everyday clinical practice, a 3 x 2 contingency table was constructed and manually defined. We found that a serum IL-6 ≥ 13 pg/mL can be regarded as indicating infection: its positive-predictive value is 90.9%. A serum IL-6 ≤ 8 pg/mL can be regarded as indicating an absence of infection: its negative predictive value is 92.1%. The serum IL-6 level seems to be a reasonable marker for identifying persistent infection after the first stage of a revision joint arthroplasty and before attempting re-implantation.