Comparative study of a non-radiometric BACTEC system and a conventional blood culture system in a clinical microbiology laboratory.

The BACTEC NR730 blood culture system is a commercially available system which utilizes infrared spectrophotometry to detect bacterial growth in broth media inoculated with the blood specimen. The objective of this study is to compare this system with the conventional system used in our laboratory. A total of 479 blood samples were collected from adult patients in the Klang TAR Hospital and inoculated simultaneously into the two systems. Clinically significant isolates were recovered from 59 (12.3%) specimens by one or both systems yielding a total of 65 isolates of which 41 isolates were recovered in both systems, 18 in BACTEC only and 6 in the conventional system (P < 0.01). Of the 40 (8.3%) blood cultures that were judged as contaminated, 2 were found in both systems, 12 in the BACTEC only and 26 in the conventional system. After 48 hours (day 2) the BACTEC system had recovered 93.2% of the total significant isolates while the conventional system recovered 61.7% only. Our results showed that the BACTEC system yielded more significant isolates in a shorter time and with a lower incidence of contamination as compared to the conventional system.