Instrumented Approaches to Performing Blood Cultures

The Bactec®system utilizes blood specimens inoculated into broth, as is the case with conventional nonradiometric broth blood cultures; however, the detection of microorganisms when present in blood culture bottles is accomplished with the Bactec®instrument. Since the inception of the Bactec®radiometric blood culture system, several other instrumented approaches to the detection of bacteremia and fungemia have been developed. These include techniques based on microcalorimetry pH monitoring of electrical potentials, colorimetry, flow cytometry, filtration-bioluminescence, electrical impedence measurements, and infrared detection of CO₂. The chapter examines the utility of these instrumented approaches to performing blood cultures. The Bactec®blood culture system is based on the measurement of C-labeled CO₂ in the head-space air of blood culture bottles containing tryptic soy broth, various growth supplements, and C-labeled growth substrates. Advantage of the Bactec®system is the possibility for automatic storage and tabulation of the results of large numbers of blood cultures via direct linkage with a data management system.