Evaluation of the MB/BacT system and comparison to the BACTEC 460 system and solid media for isolation of mycobacteria from clinical specimens

Abstract

The MB/BacT automated system is designed for the isolation of mycobacteria from clinical specimens. It utilizes a colorimetric sensor and reflected light to continuously monitor the CO 2 concentration in the culture medium. We compared its performance to that of the BACTEC 12B media for the radiometric BACTEC 460 instrument and that of solid culture media. Respiratory specimens and urine samples were decontaminated with 4% NaOH. The vials of the two instruments were inoculated with 500 l of sample and two solid egg-based media at 200 l each. All vials were incubated at 37°C for 6 weeks. A total of 1,078 specimens (633 respiratory specimens, 78 cerebrospinal fluid specimens, 177 other body fluid specimens, 87 urine specimens, and 103 other types of specimens) were cultured in parallel. Mycobacteria could be identified from 73 (6.8%) specimens: 67 M. tuberculosis, 3 M. kansasii, 1 M. xenopi, 1 M. terrae, and 1 mixed M. avium with M. scrofulaceum. Of these, 63 (86.3%) specimens were positive with the MB/BacT system, 67 (91.8%) were positive with the BACTEC 460 instrument, and 58 (79.5%) were positive with the two egg-based media. MB/BacT cultures were positive on average after 17.5 (؎6.4) days, BACTEC cultures with a growth index of >20 (mean, 200) were positive after 14.3 (؎8.2) days, and egg-based media were positive after 24.2 (؎7.5) days. Microorganisms other than mycobacteria contaminated 46 (4.3%) MB/BacT cultures and 31 (2.9%) BACTEC cultures, which had to be discarded. The MB/BacT system is a well-automated system for the detection of M. tuberculosis in clinical specimens without using radioactive reagents. Further trials are required to determine whether it is suitable for the culture of nontuberculous mycobacteria.

Evaluation of the MB/BacT System for recovery of mycobacteria from clinical specimens in comparison to Lowenstein-Jensen medium

“…Published rates of Mycobacterium spp. recovery range from 73.0% to 96.5% for the MB/BacT system [9][10][11][12][13] and 53.6% to 95.9% for the LJ culture system [10][11][12][13].…”

Evaluation of the BacT/ALERT 3D system for recovery and drug susceptibility testing of Mycobacterium tuberculosis

“…However, this system has limitations, such as the necessity of daily manual loading, the possibility of cross‐contamination due to the invasive reading, manual data management, and the creation of radioactive waste. Novel non‐radiometric systems based on liquid culture have been developed with the aim of avoiding these drawbacks [3–5]. One of them is the BacT/ALERT 3D system [6] (bioMérieux, Durham, NC, USA), which is based on the detection of CO 2 released by actively proliferating mycobacteria into the liquid media.…”

Comparison of Recoveries of Mycobacterium tuberculosis Using the Automated BACTEC MGIT 960 System, the BACTEC 460 TB System, and Löwenstein-Jensen Medium

“…Automation of the cultivation process is high on the list of priorities for laboratories dealing with large specimen loads. Although the recently developed MB/BacT (Organon Teknika, Turnhout, Belgium) and ESP II (Difco Laboratories, Detroit, Mich.) culture systems provide a fully automated, walk-away cultivation process, the capacity of these instruments is rather low (MB/BacT, 240 vials per instrument; ESP II, 384 vials per instrument) (1,6,9,11). Therefore, several units are required, which might be expensive even for laboratories in high-income countries.…”