Cord formation in BACTEC medium is a reliable, rapid method for presumptive identification of Mycobacterium tuberculosis complex

Serpentine cord formation in BACTEC 12B medium was evaluated as a rapid method for the presumptive identification of M. tuberculosis complex. Kinyoun acid-fast stained smears were prepared from 666 positive BACTEC 12B bottles and examined for the presence or absence of serpentine cording. Cord formation had a sensitivity, specificity, positive predictive value, and negative predictive value of 89.2, 99.2, 98.5, and 94.2%, respectively. The evaluation of the presence of cord formation in BACTEC 12B medium is reliable and permits the rapid presumptive reporting of M. tuberculosis.