Microbiological comparison of a new infra-red blood culture system (Bactec NR 600) and a radiometric system (Bactec 460)
Corkill, J.E.; Rimmer, K.
Medical Laboratory Sciences 44(2): 150-159
1987
ISSN/ISBN: 0308-3616 PMID: 3320664 Document Number: 287023
A new instrument utilising infra-red analysis of microbial-generated carbon dioxide was compared with a radiometric system. The study had two phases: (1) a laboratory evaluation of 96 bacterial strains in simulated blood cultures, and (ii) a prospective comparison of 778 paired blood cultures taken from immunocompromised patients. Combined results for all bacteria in simulated blood culture showed no significant difference in mean isolation times with aerobic media, but a significant difference in anaerobic media. Gram-positive bacteria were recovered at similar rates from both test systems, but Gram-negative bacteria showed a greater disparity in recovery times, particularly between anaerobic media. From 64 septicaemic episodes, absolute numbers of bacteria recovered and speed of primary isolation were equivalent in both systems. At 24 h, 83.9% of all positive were detected with the infra-red system and 79.3% with the radiometric system, and (depending on the threshold breakpoints chosen) biological false-positives ranged from 6.5 to 9.9% and 1.0 to 12.9% respectively.