ABSTRACT
A concentration of specimen is recommended for the effective recovery of Mycobacterium tuberculosis [MTB], but the bacteriological efficiency is not well evaluated. The present study evaluated the factors contributing to concentration efficiency of centrifugation and bead-based technique [TB-Beads; Microsens, UK] to recover MTB by using simple in vitro specimens. Four specimens were prepared [6.5 × 103; 8.1 × 104; 7.9 × 105; and 6.4 × 106 cfu/mL] of different concentrations with or without 5 × 104 of THP-1 cells [RIKEN BRC, Japan]. Specimens were subjected to centrifugation at 2000, 3000, and 4000g for 15 min, and to TB-Beads. The concentration and recovery rate were calculated to evaluate the efficiency of each method. The specimens containing a higher number of bacteria and THP-1 cells had a tendency to yield a higher concentration and recovery rate [p = 0.001-0.083]. MTB was recovered more efficiently with THP-1 cells from the 6.5 × 103 cfu/mL specimen by centrifugation [p= 0.001] than without them; 24.7-54.4% of MTB were recovered with THP-1 cells by centrifugation at 3000g for 15 min, while the recovery using TB-Beads was a maximum of 12.7%. The efficiency of centrifugation depends on the bacterial density and the co-existence of THP-1 cells. The efficiency of TB-Beads was not as high as centrifugation