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Cord formation in BACTEC(TM) medium aids rapid identification of Mycobacterium tuberculosis complex
G A O'Hara1, S Abdullah2, D D Creer3
1Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK.
Abstract:
Mycobacterium tuberculosis complex (MTC) organisms form serpentine cords in fluid culture medium. Reporting of a presumptive identification of MTC based on cording allows rapid identification of patients with tuberculosis. A total of 612 positive mycobacterial cultures from 316 patients over 3 years (2008-2010) were evaluated for the presence of cord formation. Cording was identified in 426 (69.6%) specimens, while the reference laboratory confirmed M. tuberculosis in 424 specimens (69.3%). Sensitivity of the test in our laboratory was 99.1% (95%CI 97.4-99.7) and specificity was 96.8% (95%CI 92.8-98.7). Presumptive identification of M. tuberculosis by the presence of cording formation is both sensitive and specific.
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