Evaluation of three culture media and their combinations for the isolation of Mycobacterium tuberculosis from pleural aspirates of patients with tuberculous pleurisy.

The abilities of three culture systems to detect Mycobacterium tuberculosis from 480 pleural aspirate specimens in 347 patients were compared. The systems were the Bactec 12B radiometric detection system (Bactec 12B), the Middlebrook 7H9 broth (7H9), and two solid media including one pyruvate enriched Lowenstein-Jensen slope (LJP) and one non-selective Middlebrook 7H11 agar slope (7H11). In the 116 specimens obtained from 85 patients of confirmed pleural tuberculosis for the isolation of Mycobacterium tuberculosis, the diagnostic yields were 33 (39%) cases from Bactec 12B, 24 (28%) cases from 7H9 and 21 (25%) cases from LJP/7H11, with median detection times of 18, 47.5 and 44 days respectively. Thirteen isolates were recovered by the Bactec 12B only, 9 by the 7H9 broth only, and 2 by the LJP/7H11 agar only. The use of a combination of the three culture systems substantially increased the diagnostic yield to 47% over the individual systems. These results show that a significantly greater and faster diagnostic yield can be obtained by including Bactec 12B in pleural aspirate cultures for the recovery of Mycobacterium tuberculosis.