Microcalorimetry as a tool for evaluation of blood culture media

Evaluation of optimal compositions of blood culture media has called for extensive and laborious work in comparative studies of large series of clincal specimens. Bacterial growth is accompanied by heat production, and calorimetry provides an analytical tool for its detection and quantification. A twin microcalorimeter of the heat conduction type was used to register heat effects in experimentally infected blood cultures. When studying Escherichia coli and Staphylococcus aureus, larger heat effects were produced with 0.05% sodium polyanetholsulfonate than with 600 IU of heparin per ml, which was also the case when using 10% sucrose. The addition of IsoVitaleX (BBL) increased the heat effects produced by the two species mentioned, whereas it had the opposite effect in cultures of Neisseria meningitidis. The present study indicates that microcalorimetry is a valuable and time-saving tool for the evaluation of optimal compositions of bacterial culture media.