In the study of upper respiratory infections, nose and throat cultures for beta hemolytic streptococci3 are essential. Since group A streptococci are implicated in human respiratory infections more than other groups, it is important that streptococci recovered on culture be identified as belonging to group A or not. The finding of streptococci which belong to groups other than A in the nose or throat usually is interpreted as being of little or no clinical or epidemiological importance.

A rapid procedure for the quantitative determination of extracellular water in bulk bakers' yeast was developed on the basis of the solute dilution principle. A reagent is prepared by synthesizing the diazonium ion of p -aminobenzoic acid and coupling it to peptone. This “azopeptone reagent” permits direct colorimetric measurement, which accounts for the rapidity and simplicity of the test. Potential errors due to osmotic effects are avoided by supplementing the reagent with saline and, more importantly, minimizing the duration of contact between reagent and cells. The new method has acceptable accuracy and precision, and may also be suitable for use with other microorganisms.