Blood culture technique: current controversies.

Currently controversial questions include: what is the optimal volume of blood for culture and which blood culture system is most suitable for the rapid and reliable detection of important pathogens? The author has discussed these topics and recommends the following: (1) At least 10 ml blood should be cultured for each set from an adult but the maximum possible volume, up to 30 ml, should be cultured. This is especially advisable when febrile immunocompromised patients and patients with infective endocarditis are investigated. (2) The best routine system for obtaining rapid and reliable blood culture results involves the use of two aerobic diphasic media and one anaerobic broth for the culture of 20 ml blood per set. Two blind subcultures are recommended during the first 24 h incubation. This conventional system is impracticable for some laboratories that process enormous numbers of blood cultures and for these laboratories the infrared Bactec system is recommended. (3) An additional blood culture method, such as the lysis-centrifugation system, should be used together with the routine system when clinical circumstances suggest the need to isolate particular 'difficult organisms' and to facilitate the culture of the maximum volume of blood. (4) It is preferable that the routine system includes one bottle without Liquoid as Liquoid-sensitive organisms may otherwise be inhibited even when gelatin is included in the medium.