Comparison of BACTEC and MGIT systems for detection of M. paratuberculosis

摘要

The BACTEC 460 system (modified 12B medium and 460 instrument) was the first liquid culture system adapted for detection of M. paratuberculosis (M. ptb.). It has proven to be fast and reliable for both detection and quantification of the organism from clinical samples. This system is no longer in commercial production and has been replaced with a non-radiometric system; a culture medium designed specifically for M. paratuberculosis growth called the Mycobacterial Growth Indicator Tube (MGIT) paraTB and an instrument, the MGIT 960. The purpose of the present study was a head-to-head comparison of the BACTEC 460 and MGIT 960 systems on 1,128 consecutively submitted clinical samples (feces and tissues). The samples originated from domestic and wild animals from diverse locations (21 U.S. states). Samples were split into two portions and processed using the previously described HPC-filter concentration protocol. All cultures that gave a positive signal in their respective instrument were subcultured on a blood agar plate to detect contaminating microbes and stained (Ziehl-Neelsen) for detection of acid-fast bacteria (AFB). AFB-positive cultures were subcultured to HEY with and without mycobactin and also tested by multiplex PCR to identify M. paratuberculosis. In total, 921 (81.6%) of samples were signal-negative by both systems.