Background Surgical site infection (SSI) ranges from 1.9% to 5.5% in most large series. Minimally invasive surgery (MIS) has been postulated to reduce SSI rates. Questions/purposes (1) Is MIS associated with a lower incidence of SSI compared with open spinal surgery? (2) Are there other independent risk factors associated with SSI? (3) What bacteria are most common in spinal SSI? Methods Medical records of 2299 patients who underwent transforaminal lumbar interbody fusion, laminectomy, or discectomy were analyzed and selected for a nested casecontrol analysis. Twenty-seven cases with SSI were matched with 162 control subjects without SSI stratified based on procedure performed within 28 days of the case's date of surgery. Patients were identified from an institutional database at a tertiary care hospital. MIS involved spinal procedures performed through a tubular retractor system. Univariate and multivariate analyses were performed.Results Patients undergoing open spinal surgery were 5.77 times more likely to develop SSI compared with MIS approaches (odds ratio [OR], 5.77; 95% confidence interval [CI], 1.0-32.7; p = 0.048). Also, from the multivariate regression model, diabetes (OR, 4.7; 95% CI, 1.3-17.0; p = 0.018), number of levels operated on (OR, 3.5; 95% CI, 1.6-7.5; p = 0.001), and body mass index (OR, 1.2; 95% CI, 1.0-1.3; p = 0.010) were predictive of an increased risk in SSI. Staphylococcus aureus was most frequently identified, being present in 12 of 21 (52.4%) patients in whom positive cultures were obtained. Four of the 12 patients had methicillin-resistant S aureus infection. Conclusions In our series, MIS has a lower incidence of SSI. The risk factors predictive of SSI should be further evaluated in well-designed prospective trials. Level of Evidence Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The aim of metabolomics is to identify, measure, and interpret complex time-related concentration, activity, and flux of metabolites in cells, tissues, and biofluids. We have used a metabolomics approach to study the biochemical phenotype of mammalian cells which will help in the development of a panel of early stage biomarkers of heat stress tolerance and adaptation. As a first step, a simple and sensitive mass spectrometry experimental workflow has been optimized for the profiling of metabolites in rat tissues. Sample (liver tissue) preparation consisted of a homogenization step in three different buffers, acidification with different strengths of acids, and solid-phase extraction using nine types of cartridges of varying specificities. These led to 18 combinations of acids, cartridges, and buffers for testing for positive and negative ions using mass spectrometry. Results were analyzed and visualized using algorithms written in MATLAB v7.4.0.287. By testing linearity, repeatability, and implementation of univariate and multivariate data analysis, a robust metabolomics platform has been developed. These results will form a basis for future applications in discovering metabolite markers for early diagnosis of heat stress and tissue damage.

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Richard von Mises wrote Probability, Statistics and Truth on his axiomatization of probability, which is based on the collective. Although his probability theory was supplanted by Kolgomorov, this book is still relevant to the teaching of probability, statistics, and science today. This work highlights some outstanding elements of the book and describes their implications on teaching practice.