Fig 1.
Age and sex distribution of patients.
Fig 2.
PCR product of clinical isolates.
Image of PCR product amplified with RD10 primer; 1 = 1kb ladder, 2–9 = clinical culture isolates, 10 = M. bovis, 11 = M. tuberculosis, 12 = negative control (TE).
Fig 3.
MTT assay growth pattern of M. tuberculosis isolates at different INH concentration.
(a) INH 0.1 μg/ml concentration: growth of isoniazid susceptible isolates RODU mean ± SE (n = 3, first week and n = 5, second and third weeks), and isoniazid resistant isolates (n = 4, first week and n = 5, second and third weeks). (b) INH 0.2 μg/ml concentration: growth of isoniazid susceptible isolates (n = 3, first week and n = 5, second and third weeks), and resistant isolates (n = 4, first week and n = 5, second and third weeks). (c) INH 0.4 μg/ml concentration: growth of isoniazid susceptible isolates (n = 3, first week and n = 5, second and third weeks), and isoniazid resistant isolates (n = 4, first week and n = 5 second and third weeks).
Table 1.
Performance of MTT assay compared with the LJ standard proportion method (PM) in detection of M. tuberculosis clinical isolates (n = 131a).
Table 2.
Time required by direct MTT assay to detect susceptible or resistant M. tuberculosis strains to rifampicin and isoniazid.
Fig 4.
MTT assay growth pattern of M. tuberculosis isolates in different weeks incubation in drug-containing Middle brook 7H9 broth.
(a) Growth patterns of rifampicin susceptible isolates (n = 61 first week, n = 102 second week, and n = 109 third week), and rifampicin resistant isolates (n = 5 second week and n = 6 third week) measured by RODU values (mean ± SE). (b) Growth patterns of isoniazid susceptible isolates (n = 26 first week and n = 38 both in second and third weeks), and isoniazid resistant isolates (n = 6 in the second and the third weeks) measured by RODU values (mean ± SE). The difference in RODU values of resistant and susceptible isolates in each week’s incubation was statistically significant (p < 0.0001 {Mann-Whitney U test}).
Fig 5.
Visual reading of typical color change in the MTT assay.
(a) Difference in color change; YC = blank control (without bacteria and drug) with yellow color, Y = Control tube (without drug) with yellow color and corresponding OD value < 0.1, FP = Control tube with faint (light) purple color and corresponding mean OD value 0.23 ± 0.015, MP = Control tube with medium purple and corresponding mean OD value 0.51 ± 0.027, DP = Control tube with dark purple color and corresponding mean OD value 0.99 ± 0.027. (b) Susceptibility visual determination; A = Growth in drug free control tube, B = Rifampicin susceptible, D = Isoniazid susceptible. (c) Resistant visually determination; C = control tube without drug, R = rifampicin resistant, H = isoniazid resistant.