Evaluation of sucrose and magnesium sulfate as additives in aerobic blood culture medium.

Clinical blood cultures were made in duplicate in brain heart infusion broth with sodium polyanetholsulfonate and gelatin (P broth) and in the same medium with 20% sucrose (S broth). In part of the study, 0.1% magnesium sulfate was also included in the medium with sucrose (SMg broth). The results from 1,287 positive blood cultures are reported. Significant differences among the rates and speeds of isolations from these media were found in Enterobacteriaceae and Staphylococcus aureus, which were isolated more frequently from S broth and SMg broth than from P broth; in addition, recoveries were accomplished earlier (1 or more days) from S broth and SMg broth than from P broth more often than the reverse growth patterns. An additional effect of magnesium sulfate upon recoveries could not be concluded. The possible mechanisms by which sucrose promotes recoveries from clinical blood cultures are discussed.