Presumptive identification of Mycobacterium tuberculosis complex based on cord formation in BACTEC MGIT 960 medium.

ABSTRACT

We considered samples received for culture of mycobacteria using BACTEC MGIT 960 system over a period of 1 year. Tubes flagged positive by MGIT were evaluated for presence of serpentine cording. The cord formation was compared with isolates identified as Mycobacterium tuberculosis complex (MTC) based on p-nitrobenzoic acid (PNB) test. Cords were found in 591 isolates of which 584 (98.8%) were confirmed as MTC. The sensitivity and specificity of cord formation were found to be 99.7% and 89.9%, respectively.