[Determination of certain physico-chemical parameters in blood culture media]

Growth of delicate or exacting microorganisms needs the maintenance, in the culture medium, of precise and stable physicochemical conditions. In order to improve knowledge of these medium, and specially of their aerobic or anaerobic state, we measured pH, partial pressures for oxygen and carbon dioxide and glucose concentration of nine commercial blood culture media, in their natural conditions of use. Comparative study of experimental results, and study of successive fabrication lots of two of these media (brain-heart and Schaedler) reveals a great variability of physicochemical parameters, and specially of pO2 and glucose concentration, although initial composition of the media has theoretically not changed. It would be desirable that such parameters be better controlled, so as to encourage regularity of composition of blood culture media and, perhaps, their clinical efficiency.