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

Diagnostic algorithm of synovial tumors and tumor-like conditions

In this chapter, a diagnostic algorithm and essential key points for the imaging workup of synovial tumors and tumor-like conditions are provided. It should be emphasized that imaging findings should be interpreted in conjunction with relevant clinical and laboratory examination. The imaging algorithm of a joint lesion should start with a conventional radiograph to detect or exclude calcifications complemented. Doppler-ultrasound examination is useful to diagnose or rule out benign synovial lesions such as ganglion or synovial cysts or inflammatory or posttraumatic synovial lesions. Ultrasound is particularly helpful for superficially located cystic lesion. If the lesion is deeply located or has no definite benign characteristics on these imaging modalities or cannot be characterized as a pseudotumoral or inflammatory lesion, MRI is mandatory. If MRI findings are equivocal or suggestive of malignancy, (imaging-guided) biopsy and subsequent histopathological examination have to be performed in a tertiary referral center following multidisciplinary discussion