Validation of diet and urinary excretion derived estimates of sodium excretion against 24-h urine excretion in a worksite sample.

BACKGROUND AND AIMS: To validate diet and urinary excretion derived estimates of sodium intake against those derived from 24-h urine collections in an Irish manufacturing workplace sample. METHODS AND RESULTS: We have compared daily sodium (Na) excretion from PABA validated 24-h urine collections with estimated daily sodium excretion derived from the following methods: a standard Food Frequency Questionnaire (FFQ), a modified 24-h dietary recall method, arithmetic extrapolations from morning and evening spot urine samples, predicted sodium excretion from morning and evening spot urine samples using Tanaka's, Kawasaki's and the INTERSALT formula. All were assessed using mean differences (SD), Bland-Altman plots, correlation coefficients and ROC Area under the Curve (AUC) for a cut off of ≥100 mmol of Na/day. The Food Choice at Work study recruited 802 participants aged 18-64 years, 50 of whom formed the validation sample. The mean measured 24-h urinary sodium (gold standard) was 138 mmol/day (8.1 g salt). At the group level, mean differences were small for both dietary methods and for the arithmetic extrapolations from morning urine samples. The Tanaka, Kawasaki and INTERSALT methods provided biased estimates of 24-h urinary sodium. R(2) values for all methods ranged from 0.1 to 0.48 and AUC findings from 0.57 to 0.76. CONCLUSION: Neither dietary nor spot urine sample methods provide adequate validity in the estimation of 24-h urinary sodium at the individual level. However, group mean errors from dietary methods are small and random and compare favourably with those from spot urine samples in this population.

Transformation of Zymomonas mobilis by a hybrid plasmid.

The transformation of Zymomonas mobilis by plasmid DNA was achieved using a modification of the CaCl2 method for Escherichia coli. The highest frequency of transformation obtained was 5 X 10(3) transformants/micrograms DNA. The success of the method depended upon the use of a plasmid which is a cointegrate between a Z. mobilis cryptic plasmid and an E. coli plasmid carrying two selectable drug resistance markers.

Antibacterial activity of different Zymomonas mobilis strains.

Twenty different Zymomonas mobilis strains were found to produce a substance which inhibited or killed various other Zymomonas , Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa strains. This antibacterial activity could be detected in cross-streak tests and as zones of clearing in lawns of the test bacteria. When Zymomonas strains are used as recipients in conjugation experiments, their antibacterial activity can be used to advantage for removal of unwanted donor cells from the mating mixtures.