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

Relation between the Supplemental Nutritional Assistance Program cycle and dietary quality in low-income African Americans in Baltimore, Maryland

Background: There has been limited research regarding the Supplemental Nutritional Assistance Program (SNAP) and recipients' dietary quality during the days and weeks after benefit disbursement.Objective: We examined the relation between participants' stages in the SNAP cycle and their macronutrient consumption, Healthy Eating Index (HE!) scores, and fruit and vegetable intake.Design: in this cross-sectional study, we analyzed single 24-h dietary recalls collected from 244 African American SNAP participants recruited near 24 corner stores in Baltimore City. A multiple linear regression analysis and bootstrapping were used.Results: Among participants who received a SNAP benefit 15 d before being surveyed, energy intake (1.35%; 95% CI: 0.01%, 2.73%), energy intake adjusted for minimum energy requirements (3.86%; 95% CI: 0.06%. 7.96%), total fat intake (1.96%; 95% CI: 0.29%, 3.8%), saturated fat intake (2.02%; 95% Cl: 0.23%, 4.01%), and protein intake (2.09%; 95% Cl: 0.70%, 3.62%) were higher per each 1-d increase in the TSSD.Conclusions: These findings suggest that the relation between the TSSD and macronutrient intake might be U-shaped, with higher intake of calories, fat, and protein in individuals in the very early and late stages of their SNAP cycles. Foods high in these nutrients might be cheaper, more accessible, and have a longer shelf-life than healthier options, such as fruit, vegetables, and whole grains, for SNAP participants when their benefits run out. Additional efforts are needed to investigate the effect of the TSSD on dietary intake by using a longitudinal design and to improve the quality of dietary intake in African American SNAP participants.National Heart, Lung, and Blood InstituteKruse Family Publications AwardJohns Hopkins Sch Publ Health, Dept Int Hlth, Baltimore, MD USAJohns Hopkins Sch Publ Health, Dept Hlth Behav & Soc, Baltimore, MD USAUniversidade Federal de São Paulo, Dept Hlth Sci, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Hlth Sci, São Paulo, BrazilNational Heart, Lung, and Blood Institute: 1R21HL102812-01A1Web of Scienc