In the vast majority of institutions, most blood culture
specimens delivered to the laboratory are entered into an
incubation protocol on a continuously monitored blood
culture device. There are several manufacturers of such
devices, and their performance characteristics are similar [27–
35]. These devices incubate the blood culture bottles for a
prescribed period of time (determined by the user) and signal
audibly and/or visually if growth is detected.
Each automated blood culture system has its own associated
medium formulations that must be selected by the user.
The blood culture bottles typically contain proprietary
mixtures of culture medium, an anticoagulant, and, in many
cases, resins or charcoal mixtures to reduce the effects of
antimicrobials and other toxic compounds. Generally, combinations
of medium formulations that are complementary to
each other are chosen to enhance the recovery of the most
diverse range of microorganisms. Medium combinations typically
include aerobic and anaerobic formulations and, in select
circumstances, a formulation containing reagents that are ideal
for recovering mycobacteria and/or yeasts may be inoculated
as well. Controlled studies comparing the performance of
media with and without the addition of antimicrobial binding
or absorbing agents (resins and/or charcoal compounds) have
repeatedly demonstrated that the latter formulations are
clearly superior for the recovery of microorganisms, especially
staphylococci and yeasts [29,34–37].
Blood cultures entered into automated, continuous-monitoring
protocols should routinely be incubated for 5 days.
Multiple studies have shown that this incubation time is
adequate for the detection of the majority of pathogens,
including fastidious bacteria that belong to the Haemophilus