Factors contribute to efficiency of specimen concentration of Mycobacterium tuberculosis by centrifugation and magnetic beads

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

First Susceptibility Testing of <i>Mycobacterium tuberculosis</i> for Second-line Anti-tuberculosis Drugs in Ghana

We performed drug susceptibility testing on first- and second-line drugs in <i>Mycobacterium tuberculosis</i> (<i>M. tuberculosis</i>) for the first time in Ghana to obtain preliminary data on drug-resistant tuberculosis. Of 21 isolates (4 new cases and 17 treated cases), 5 (23.8%) were multi-drug resistant tuberculosis (MDR-TB) and 19 (90.5%) were resistant to at least one drug, but no extensively drug-resistant TB (XDR-TB) was identified. Since the target patients were Category II, IV or smear positive at follow-up microscopy, it is understandable that there were many drug-resistant TB cases. Six isolates were resistant to one or two second-line drugs, but the second-line drugs were not approved in Ghana. It is considered that the bacilli were imported from abroad. Preventing the import of drug-resistant TB bacilli is probably one of best ways to control TB in Ghana.