Evaluation of the new improved BHI-lysis blood culture medium for the BCB Roche system.

The new BHI-lysis blood culture medium for the BCB system (BCB release, Hoffmann-La Roche), which lyses blood cells, was compared with the BHI-S broth of the same BCB system and the Signal system (Oxoid). A total of 2394 sets consisting of three bottles were each inoculated with 7 ml of blood at the bedside. In the laboratory agar-coated paddles were attached to the BHI-lysis and the BHI-S bottles, and the Signal device was mounted onto the Oxoid bottle. All systems were incubated at 35 degrees C for seven days. Of the 309 (13%) positive sets, 73 (3%) were contaminated and in 242 (10%) sets a total of 250 pathogenic microorganisms were isolated. These could be grown significantly more often from the BHI-lysis bottle (n = 213) than from either the BHI-S (n = 189) or Signal bottle (n = 176). No significant differences in the time needed to achieve a positive result was noted between the BHI-lysis and BHI-S bottles, but comparison of the BHI-lysis and Signal bottles revealed that overall pathogens were detected earlier significantly more often with the BHI-lysis bottle. In view of the good performance of blood culture broths containing lysing agents, their wider use is warranted in future.