TRICORE, a novel bead-based specimen concentration method for the culturing of Mycobacterium tuberculosis

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

BACKGROUND

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.

METHODS

Four specimens were prepared (6.5×10(3); 8.1×10(4); 7.9×10(5); and 6.4×10(6)cfu/mL) of different concentrations with or without 5×10(4) of THP-1 cells (RIKEN BRC, Japan). Specimens were subjected to centrifugation at 2000, 3000, and 4000g for 15min, and to TB-Beads. The concentration and recovery rate were calculated to evaluate the efficiency of each method.

RESULTS

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 6.5×10(3)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 15min, while the recovery using TB-Beads was a maximum of 12.7%.

CONCLUSIONS

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.

Nucleic acid testing for tuberculosis at the point-of-care in high-burden countries

Early diagnosis of tuberculosis (TB) facilitates appropriate treatment initiation and can limit the spread of this highly contagious disease. However, commonly used TB diagnostic methods are slow, often insensitive, cumbersome and inaccessible to most patients in TB endemic countries that lack necessary resources. This review discusses nucleic acid amplification technologies, which are being developed for rapid near patient TB diagnosis, that are in the market or undergoing clinical evaluation. They are based on PCR or isothermal methods and are implemented as manual assays or partially/fully integrated instrument systems, with associated tradeoffs between clinical performance, cost, robustness, quality assurance and usability in remote settings by minimally trained personnel. Unmet needs prevail for the identification of drug-resistant TB and for TB diagnosis in HIV-positive and pediatric patients.

Magnetic bead protocol for culturing Mycobacterium tuberculosis from sputum specimens

A magnetic bead protocol and a standard centrifugation protocol yielded Mycobacterium tuberculosis in 40/50 sputum specimens in 12 ± 1 days and 11 ± 2 days, respectively (P > 0.05 by Student's t test). Manipulation took 35 ± 5 min and 45 ± 10 min, respectively (P < 0.05). The magnetic bead protocol could advantageously replace centrifugation for culturing M. tuberculosis from sputum.