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

Effectiveness of silver-impregnated central venous catheters for preventing catheter-related blood stream infections: a meta-analysis

Objectives: The purpose of this meta-analysis was to examine the effectiveness of silver-impregnated central venous catheters (CVCs) in preventing catheter bacterial colonization and catheter-related blood stream infections (CRBSIs). Methods: PubMed, Cochrane, and Embase databases were searched up to April 30, 2014. Studies in which other antiseptic reagents were used (e.g., chlorhexidine, octenidine dihydrochloride, urokinase rinses, benzalkonium chloride, rifampin–minocycline) were excluded. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Tests of heterogeneity and publication bias were performed. Results: Twelve studies were included in the meta-analysis. The studies enrolled a total of 2854 patients; 1440 received a standard CVC and 1414 received a silver-impregnated CVC. No significant difference in catheter bacterial colonization rates was found between silver-impregnated and standard CVCs (OR 0.907, 95% CI 0.758–1.087, p = 0.290). No significant difference in CRBSI rates was found between silver-impregnated and standard CVCs (pooled OR 0.721, 95% CI 0.476–1.094, p = 0.124). No significant heterogeneity or publication bias was noted. Conclusions: Silver-impregnated CVCs are not associated with reduced rates of bacterial colonization or CRBSI

Evaluation of Bacterial Expansin EXLX1 as a Cellulase Synergist for the Saccharification of Lignocellulosic Agro-Industrial Wastes

<div><p>Various types of lignocellulosic wastes extensively used in biofuel production were provided to assess the potential of EXLX1 as a cellulase synergist. Enzymatic hydrolysis of natural wheat straw showed that all the treatments using mixtures of cellulase and an optimized amount of EXLX1, released greater quantities of sugars than those using cellulase alone, regardless of cellulase dosage and incubation time. EXLX1 exhibited different synergism and binding characteristics for different wastes, but this can be related to their lignocellulosic components. The cellulose proportion could be one of the important factors. However, when the cellulose proportion of different biomass samples exhibited no remarkable differences, a higher synergism of EXLX1 is prone to occur on these materials, with a high proportion of hemicellulose and a low proportion of lignin. The information could be favorable to assess whether EXLX1 is effective as a cellulase synergist for the hydrolysis of the used materials. Binding assay experiments further suggested that EXLX1 bound preferentially to alkali pretreated materials, as opposed to acid pretreated materials under the assay condition and the binding preference would be affected by incubation temperature.</p></div