Population-based survey of human sodium and potassium excretion.

1. During the 1989 National Heart Foundation Risk Factor Prevalence Survey a subsample in Hobart collected 24 h urine samples to measure electrolyte excretion. 2. The ranges were 30-344 mmol/24 h for Na+ excretion (mean 160 mmol/24 h for men, 124 mmol/24 h for women), and 25-119 mmol/24 h for K+ excretion (mean 77 mmol/24 h for men, 68 mmol/24 h for women). 3. As in other surveys, women excreted about 20-25% less Na+ and K+ than men, although there was no significant sex difference in the ratio of Na+/K+ excretion. 4. The recommended dietary intake (RDI) for Na+ and K+ was followed simultaneously by 19% of subjects, and 13% had a 24 h urinary Na+/K+ ratio less than or equal to 1.0. 5. Observance of the RDI limited the value of iodized salt for goitre prophylaxis. 6. Sodium excretion rates were outside the therapeutic range of thiazide diuretics in 22% of subjects. 7. Diet groups for long-term prospective cohort studies to test the prophylactic value of avoiding salt could apparently be recruited from existing subsamples of the population.

3-Dimensional susceptibility testing of beta-lactam antibiotics.

A technique for demonstrating the substrate specificities of bacterial beta-lactamases is presented. Enzymatic degradation of beta-lactam antibiotics can be detected by cutting a wall of inoculum into the agar 3 mm from an antibiotic disc. Inactivation of the drug as it diffuses through the wall of inoculum results in distortion of the resulting inhibition zone. This procedure can be applied to the Stokes, Bauer-Kirby, International Collaborative Study (ICS) and Calibrated Dichotomous Sensitivity Test (CDS) methods so that they provide information about any detrimental effect of a pathogen on beta-lactam antibiotics, in addition to the effect the antibiotics have on the pathogen. The additional information generated by this simple procedure should increase the predictive value of in-vitro tests.