Genetic and biochemical analyses of chromosome and plasmid gene homologues encoding ICL and ArCP domains in Vibrioanguillarum strain 775

Anguibactin, the siderophore produced by Vibrio anguillarum 775 is synthesized from 2,3-dihydroxybenzoic acid (DHBA), cysteine and hydroxyhistamine via a nonribosomal peptide synthetase (NRPS) mechanism. Most of the genes encoding anguibactin biosynthetic proteins are harbored by the pJM1 plasmid. In this work we report the identification of a homologue of the plasmid-encoded angB on the chromosome of strain 775. The product of both genes harbor an isochorismate lyase (ICL) domain that converts isochorismic acid to 2,3-dihydro-2,3-dihydroxybenzoic acid, one of the steps of DHBA synthesis. We show in this work that both ICL domains are functional in the production of DHBA in V. anguillarum as well as in E. coli. Substitution by alanine of the aspartic acid residue in the active site of both ICL domains completely abolishes their isochorismate lyase activity in vivo. The two proteins also carry an aryl carrier protein (ArCP) domain. In contrast with the ICL domains only the plasmid encoded ArCP can participate in anguibactin production as determined by complementation analyses and site-directed mutagenesis in the active site of the plasmid encoded protein, S248A. The site-directed mutants, D37A in the ICL domain and S248A in the ArCP domain of the plasmid encoded AngB were also tested in vitro and clearly show the importance of each residue for the domain function and that each domain operates independently.

Clustering in surgical trials : database of intracluster correlations

PMID: 22217216 [PubMed - indexed for MEDLINE] PMCID: PMC3311136 Free PMC ArticlePeer reviewedPublisher PD

Fatigue strength of common tibial intramedullary nail distal locking screws

Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws

The challenges faced in the design, conduct and analysis of surgical randomised controlled trials

Randomised evaluations of surgical interventions are rare; some interventions have been widely adopted without rigorous evaluation. Unlike other medical areas, the randomised controlled trial (RCT) design has not become the default study design for the evaluation of surgical interventions. Surgical trials are difficult to successfully undertake and pose particular practical and methodological challenges. However, RCTs have played a role in the assessment of surgical innovations and there is scope and need for greater use. This article will consider the design, conduct and analysis of an RCT of a surgical intervention. The issues will be reviewed under three headings: the timing of the evaluation, defining the research question and trial design issues. Recommendations on the conduct of future surgical RCTs are made. Collaboration between research and surgical communities is needed to address the distinct issues raised by the assessmentof surgical interventions and enable the conduct of appropriate and well-designed trials.The Health Services Research Unit is funded by the Scottish Government Health DirectoratesPeer reviewedPublisher PD

Different competing risks models applied to data from the Australian Orthopaedic Association National Joint Replacement Registry

Purpose: Here we describe some available statistical models and illustrate their use for analysis of arthroplasty registry data in the presence of the competing risk of death, when the influence of covariates on the revision rate may be different to the influence on the probability (that is, risk) of the occurrence of revision. Patients and methods: Records of 12,525 patients aged 75–84 years who had received hemiarthroplasty for fractured neck of femur were obtained from the Australian Orthopaedic Association National Joint Replacement Registry. The covariates whose effects we investigated were: age, sex, type of prosthesis, and type of fixation (cementless or cemented). Extensions of competing risk regression models were implemented, allowing the effects of some covariates to vary with time. Results: The revision rate was significantly higher for patients with unipolar than bipolar prostheses (HR = 1.38, 95% CI: 1.01–1.89) or with monoblock than bipolar prostheses (HR = 1.45, 95% CI: 1.08–1.94). It was significantly higher for the younger age group (75–79 years) than for the older one (80–84 years) (HR = 1.28, 95% CI: 1.05–1.56) and higher for males than for females (HR = 1.37, 95% CI: 1.09–1.71). The probability of revision, after correction for the competing risk of death, was only significantly higher for unipolar prostheses than for bipolar prostheses, and higher for the younger age group. The effect of fixation type varied with time; initially, there was a higher probability of revision for cementless prostheses than for cemented prostheses, which disappeared after approximately 1.5 years. Interpretation: When accounting for the competing risk of death, the covariates type of prosthesis and sex influenced the rate of revision differently to the probability of revision. We advocate the use of appropriate analysis tools in the presence of competing risks and when covariates have time-dependent effects.Marianne H Gillam, Amy Salter, Philip Ryan, and Stephen E Grave

Adherence to a femoral neck fracture treatment guideline

Purpose: In 2007 the Dutch Surgical Society published a clinical practice guideline for the treatment of hip fracture patients, based on the best available international evidence at that time. We investigated to what extent treatment of femoral neck fracture patients in the Netherlands corresponded with these guidelines, and determined differences in patient characteristics between the treatment groups. Methods: All femoral neck fracture patients treated in 14 hospitals between February 2008 and August 2009 were included. Patient characteristics, X-rays, and treatment data were collected retrospectively. Results: From a total of 1,250 patients 59 % had been treated with arthroplasty, 39 % with internal fixation, and 2 % with a non-operative treatment. While 74 % of the treatment choices complied with the guideline, 12 % did not. In 14 % adherence could not be determined from the available data. Arthroplasty was preferred over internal fixation in elderly patients with severe comorbidity, pre-fracture osteoporosis and a displaced fracture, who were ambulatory with aids pre-fracture (odds ratio, OR 2.2-58.1). Sliding hip screws were preferred over cancellous screws in displaced fractures (OR 1.9). Conclusions: Overall guideline adherence was good. Most deviations concerned treatment of elderly patients with a displaced fracture and implant use in internal fixation. Additional data on these issues, preferably at a higher scientific level of evidence, is needed in order to improve the guideline and to reinforce a more uniform treatment of these patients

Outcome analysis following removal of locking plate fixation of the proximal humerus

<p>Abstract</p> <p>Background</p> <p>Concerning surgical management experience with locking plates for proximal humeral fractures has been described with promising results. Though, distinct hardware related complaints after fracture union are reported. Information concerning the outcome after removal of hardware from the proximal humerus is lacking and most studies on hardware removal are focused on the lower extremity. Therefore the aim of this study was to analyze the functional short-term outcome following removal of locking plate fixation of the proximal humerus.</p> <p>Methods</p> <p>Patients undergoing removal of a locking plate of the proximal humerus were prospectively followed. Patients were subdivided into the following groups: Group HI: symptoms of hardware related subacromial impingement, Group RD: persisting rotation deficit, Group RQ: patients with request for a hardware removal. The clinical (Constant-Murley score) and radiologic (AP and axial view) follow-up took place three and six months after the operation. To evaluate subjective results, the Medical Outcomes Study Short Form-36 (SF-36), was completed.</p> <p>Results</p> <p>59 patients were included. The mean length of time with the hardware in place was 15.2 ± 3.81 months. The mean of the adjusted overall Constant score before hardware removal was 66.2 ± 25.2% and increased significantly to 73.1 ± 22.5% after 3 months; and to 84.3 ± 20.6% after 6 months (p < 0.001). The mean of preoperative pain on the VAS-scale before hardware removal was 5.2 ± 2.9, after 6 months pain in all groups decreased significantly (p < 0.001). The SF-36 physical component score revealed a significant overall improvement in both genders (p < 0.001) at six months.</p> <p>Conclusion</p> <p>A significant improvement of clinical outcome following removal was found. However, a general recommendation for hardware removal is not justified, as the risk of an anew surgical and anesthetic procedure with all possible complications has to be carefully taken into account. However, for patients with distinct symptoms it might be justified.</p

Population-Level Associations between Preschool Vulnerability and Grade-Four Basic Skills

Background: This is a predictive validity study examining the extent to which developmental vulnerability at kindergarten entry (as measured by the Early Development Instrument, EDI) is associated with children’s basic skills in 4th grade (as measured by the Foundation Skills Assessment, FSA). Methodology/Principal Findings: Relative risk analysis was performed on a large database linking individual-level EDI ratings to the scores the same children obtained on a provincial assessment of academic skills (FSA – Foundation Skills Assessment) four years later. We found that early vulnerability in kindergarten is associated with the basic skills that underlie populations of children’s academic achievement in reading, writing and math, indicating that the Early Development Instrument permits to predict achievement-related skills four years in advance. Conclusions/Significance: The EDI can be used to predict children’s educational trends at the population level and can help select early prevention and intervention programs targeting pre-school populations at minimum cost