[Comparison of BACTEC and BacT/ALERT systems in evaluation of blood cultures]

Automatized blood culture systems are used widely due to the characteristics such as lower contamination risks, shorter incubation periods and higher isolation rates. In this study, BACTEC 9050 (Becton Dickinson, Ireland) and BacT/ALERT 120 (Organon Teknika Corp, USA) systems were compared for the evaluation of blood cultures obtained from 222 hospitalized patients in intensive care units between September and December 2003. For this purpose, two blood samples obtained from each arms of patients, were inoculated into BACTEC plus aerobic/F (Becton Dickinson, Ireland) and BacT/ALERT FA/aerobic (BioMeriéux, USA) media, respectively, and incubated. The first bacterial growth time has been recorded for each system and the bacteria were identified by conventional methods. As a result, both of the systems detected bacterial growth in 42 (91.3%) of a total of 46 (20.7%) positive blood samples obtained from 222 patients. The distribution of microorganisms grown in BACTEC and BacT/ALERT were found as follows, respectively; 24 and 20 coagulase negative staphylococci, 8 and 8 Acinetobacter sp., 6 and 10 Escherichia coli, 1 and 1 Staphylococcus aureus, 1 and 1 Pseudomonas sp., 1 and 1 Klebsiella sp., 1 and 1 Candida sp. False positivity and false negativity were not observed in either of the systems. Positive results were obtained in an average time of 20.6 (7.5-35.5) hours and 22.49 (1.5-35.5) hours with BACTEC and BacT/ALERT, respectively. Since there was no statistically significant difference between the systems concerning bacterial isolation rates and periods (p=1.00), it may be concluded that both of these systems would be used in clinical microbiology laboratories for the evaluation of blood cultures.