Fully automated liquid culture system compared with Lowenstein-Jensen solid medium for rapid recovery of mycobacteria from clinical samples

The aim of this study was to compare the rate of recovery of mycobacteria and the time to detection in 5208 samples using the MB/BacT culture system (Organon Teknika, USA) and Lowenstein-Jensen medium. Mycobacteria were recovered from 301 (5.7%) samples. Two hundred fifty-seven (85.3%) isolates from 114 patients were Mycobacterium tuberculosis [135 (52.5%) smear-positive, 122 (47.4%) smear-negative], and 44 (14.6%) were potentially pathogenic environmental mycobacteria. The yield with the MB/BacT was higher than that with Lowenstein-Jensen [287 (95.3%) vs. 200 (66.4%), P < 0.001] for both Mycobacterium tuberculosis [247 (96.1%) vs. 187 (72.7%), P < 0.001] and potentially pathogenic environmental mycobacteria [40 (90.9%) vs. 13 (29.5%), P < 0.001], mainly at the expense of the smear-negative samples. Moreover, 70 (27.2%) samples were positive only in the MB/BacT, whereas ten (3.8%) samples were positive only in Lowenstein-Jensen. The number of patients with tuberculosis detected by the MB/BacT was higher than that detected by Lowenstein-Jensen medium [111 (97.3%) vs. 89 (78%), P < 0.001]. In 25 (21.9%) patients the diagnosis was established solely by means of the MB/BacT. In smear-positive and smear-negative samples, the mean times to detection of Mycobacterium tuberculosis were 16.7 and 26.3 days, respectively, with Lowenstein-Jensen and 11.5 and 19.3 days, respectively, with the MB/BacT. These results indicate that the MB/BacT is more efficient and faster than Lowenstein-Jensen for the recovery of mycobacteria.