Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Dilated upper sleeve can be associated with severe postoperative gastroesophageal dysmotility and reflux,”Obesity Surgery,

Abstract Background Laparoscopic sleeve gastrectomy (LSG) is an effective bariatric procedure, and it can be done as an isolated LSG or in conjunction with biliopancreatic diversion bypass/duodenal switch (laparoscopic duodenal switch; LDS). Gastroesophageal reflux after LSG has been described, but the mechanism is unknown and the treatment in the severest cases has not been discussed. We describe a cohort of patients who have underwent an LSG or LDS, and have suffered from a severe postoperative gastroesophageal motility disorder and/or reflux, report on their treatment, and discuss possible underlying mechanisms. Methods Seven hundred and six patients underwent an LSG by two of the authors (AK, AB). Sixty nine patients underwent laparoscopic sleeve gastrectomy in Hadassa