Comparison of intra-assay and inter-assay reproducibility and positive detection times of two different (BacT/Alert 3D and Autobio BC) commercial blood culture systems

Purpose

In our study, we aimed to compare the performance of the BacT/Alert 3D (bioMerieux, France) system, which is currently used in our laboratory, and the Autobio BC (Autobio, China) system, which was newly introduced in our country, using standard and clinical isolates.

Methods

Bacterial suspension was prepared by two technicians on the same day and three consecutive days from five different standard strains with 0.5 McFarland turbidity, then serial dilution to a final concentration was adjusted and was simultaneously inoculated in aerobic blood culture bottles. The bacterial concentration was measured by making a quantitative counting plate. The same procedure was also performed for 55 clinical isolates belonging to eleven species. After simulated bacteremia with standard and clinical isolates, the growth results were confirmed by inoculation from positive blood culture bottles onto solid medium and identification was made in the next day with MALDI-TOF MS (bioMérieux). In each study, sterile saline and blood was inoculated into the bottles as a negative control to check contamination. Intra-assay and inter-assay reproducibility of recovery rates and detection times of standard strains; recovery rates and detection times of clinical isolates were compared for both systems.

Results

Recovery rates were 100 % in both systems, and when positive detection times were compared, it was found that there was no difference between the two devices in clinical isolates (p:0.262) but that Autobio BC gave significantly (p < 0.001) earlier results in standard strains.

Conclusions

In our simulated bloodstream infection study, Autobio BC was found to be comparable with BacT/Alert 3D, both recovery rates and growth detection time performance were found to be very good, and it can be used in routine microbiology laboratories.