mtb reference strain atcc  (ATCC)

Journal: Scientific Reports

Article Title: A rapid culture system uninfluenced by an inoculum effect increases reliability and convenience for drug susceptibility testing of Mycobacterium tuberculosis

doi: 10.1038/s41598-018-26419-z

Figure Lengend Snippet: Activities of anti-TB TB drugs in the DAC system are not affected by inoculum size. (A) The MIC values for the first-line drugs according to various inoculum sizes. MTB H37Rv ATCC 27294 cells from ~10 4 to ~10 7 CFU/mL were inoculated in the DAC system and the MIC values were determined. The spots (circle, triangle and square) of each drug indicate the MICs values from three independently repeated experiments. The tested concentrations for each drug were a two-fold dilution scale. The breakpoints of the BACTEC 460 TB and MGIT 960 systems based on the Middlebrook 7H9 broth were adopted for the DAC system; 0.1 μg/mL for INH, 1.0 μg/mL for RIF, 1.0 μg/mL for STR, and 5.0 μg/mL for EMB. The red horizontal line indicates the breakpoints for each drug. All MIC values were determined under the breakpoints. (B) The comparison of an inoculum effect for the first-line drugs against H37Rv between the DAC system and two routine methods, the L-J method (solid) and MGIT 960 method (liquid). The various inoculum sizes from ~10 4 to ~10 7 CFU/mL were tested. The DST results were represented as resistant (R) or susceptible (S). The DST results were consistently “S” regardless of the various inoculum sizes in the DAC system, whereas they were changed from “S” to “R” or “Error” over 5 × 10 6 CFU/mL in the two routine methods. (C) The MICs values from clinical isolates in the various inoculum sizes. The MIC values from two pan-susceptible and two resistant strains were estimated for the first-line drugs. The inoculum sizes were from ~10 3 CFU/mL to ~10 8 CFU/mL for two drug susceptible strains and two drug resistant strains. There was no inoculum effect with the clinical isolates in the DAC system.

Article Snippet: To ensure the consistency of lyophilized drugs, the reference strain MTB H37Rv ATCC 27294 and the clinical isolate KIT87190 strain were used as internal controls for each test of DST .

Techniques: Comparison

Journal: Scientific Reports

Article Title: A rapid culture system uninfluenced by an inoculum effect increases reliability and convenience for drug susceptibility testing of Mycobacterium tuberculosis

doi: 10.1038/s41598-018-26419-z

Figure Lengend Snippet: Safety of the DAC system. ( A ) The DAC system is safer for researchers as it blocks the leakage of MTB cells in three ways. (1) MTB cells in the DAC chip are immobilized in the solidified agarose matrix. (2) Each well in the chip is enclosed with sealing film and (3) the DAC chip is securely covered with a locking lid. (B) The comparison of MTB H37Rv cell numbers in the culture medium between the DAC chip and the liquid culture method after inoculation. MTB cells (~4.0 × 10 5 CFU/mL) were inoculated both in the liquid culture system and in the DAC system. To perform this safety test, a 40-μL of the agarose-MTB mixture was loaded onto a DAC chip and 0.5 mL of the 7H9 medium was then added. After 1-, 3-, 5- and 7-day incubations, supernatants (50 μL) from both systems were collected using a pipette: The cells were plated on 7H11 agar plates, and 3 weeks later of culture, the bacterial cells were counted using the bacterial CFU method. In the DAC system, bacterial cells were not detected in culture broth until 1 and 3 incubation days, and there were ~1.5 × 10 2 and ~6.2 × 10 3 MTB cells on the 5th and 7th days, respectively. There were 1,000-fold fewer cells than in the liquid culture method.

Article Snippet: To ensure the consistency of lyophilized drugs, the reference strain MTB H37Rv ATCC 27294 and the clinical isolate KIT87190 strain were used as internal controls for each test of DST .

Techniques: Comparison, Transferring, Incubation