Persistently high prevalence of primary resistance and multidrug resistance of tuberculosis in Heilongjiang Province, China.

BACKGROUND: The spread of multidrug-resistant tuberculosis (MDR-TB) Mycobacterium tuberculosis (M. tuberculosis) strains has been a big challenge to the TB control and prevention in China. Knowledge about patterns of drug resistance in TB high-burden areas of China is crucial to develop appropriate control strategies. We conducted a comprehensive investigation of the resistance pattern of M. tuberculosis in Heilongjiang Province. METHODS: 1427 M. tuberculosis clinical strains were isolated from pulmonary TB patients hospitalized between 2007 and 2012. The susceptibility of the isolates to the first-line anti-TB drugs and the resistance of MDR M. tuberculosis to fluoroquinolones were examined. We also performed a statistical analysis to identify the correlated risk factors for high burden of MDR-TB. RESULTS: The global resistance rates of 2007-2012 to the first-line drugs and MDR were 57.0 and 22.8 %, respectively. Notably, the primary MDR-TB and pan-resistance rates were as high as 13.6 and 5.0 %, respectively. Of MDR M. tuberculosis isolates (2009), approximately 13 % were not susceptible to any of the fluoroquinolones tested. Being age of 35 to 54, high re-treatment proportion, the presence of cavity lesion, and high proportion of shorter hospitalization are correlated with the development of MDR-TB. CONCLUSIONS: The high prevalence of drug resistant, MDR-TB, and fluoroquinolone-resistant MDR-TB is a big concern for TB control. More importantly, in order to control the development of MDR-TB effectively, we need to pay more attention to the primary resistance. Targeting reducing the prevalence of the risk factors may lead to better TB control in China.

[Comparison of two interferon-gamma release assays in the diagnosis of tuberculosis].

OBJECTIVE: To compare the diagnostic performance of A.TB, an ELISA-based interferon-gamma release assay (IGRA), and T-SPOT.TB, an ELISPOT-based IGRA, and therefore to evaluate the value of A.TB assay in the routine clinical practice. METHODS: From March to May of the year of 2011, 112 hospitalized patients were enrolled from 2 chest hospitals in Beijing and Harbin, including 75 cases in the TB group (43 male and 32 female) with the average age of (44 ± 18) years, spanning from 28 to 57 years, and 37 cases in the non-TB group (21 male and 16 female) with the average age of (54 ± 10) years, spanning from 24 to 82 years. During the same period, 34 healthy volunteers (4 male and 30 female), with the average age of (20 ± 0.6) years, spanning from 19 to 22 years, were recruited in Beijing Chest Hospital. A head-to-head comparison of the 2 IGRAs was performed on the 146 subjects to evaluate their overall diagnostic performance. Chi-square test or Fisher's exact test was used for statistical analysis of enumeration data. RESULTS: The sensitivity and specificity of A.TB were 81.3% (61/75, 95%CI = 72.5 - 90.2) and 83.1% (59/71, 95%CI = 74.4 - 91.8) respectively, compared to 90.7% (68/75, 95%CI = 84.1 - 97.3) and 78.9% (56/71, 95%CI = 69.4 - 88.4) for T-SPOT.TB. There was no significant difference in sensitivity or specificity (chi square values were 2.77 and 0.17 respectively, both P > 0.05). The area under the ROC curve was 0.90 (95%CI = 0.84 - 0.95) for A.TB and 0.91 (95%CI = 0.86 - 0.96) for T-SPOT.TB. The observation agreement between the 2 methods was 87.2% (123/141), with a kappa value of 0.74. T-SPOT.TB produced indeterminate results at a rate of 3.4% (5/146). CONCLUSIONS: There was comparable diagnostic performance between the 2 assays. However, when compared to T-SPOT.TB, the A.TB testing procedure, with less technical demand and without requirement of well-equipped lab, is simpler and the interpretation of results is less subjective.

Genotypes and characteristics of clustering and drug susceptibility of Mycobacterium tuberculosis isolates collected in Heilongjiang Province, China.

For the last decade China has occupied second place, after India, among the top five countries with high burdens of tuberculosis (TB). Heilongjiang Province is located in northeastern China. The prevalence of drug-resistant TB in Heilongjiang Province is higher than the average level in China. To determine the transmission characteristics of Mycobacterium tuberculosis strains isolated in this area and their genetic relationships, especially among the Beijing family strains, we investigated their genotypes. From May 2007 to October 2008, 200 M. tuberculosis isolates from patients presenting pulmonary TB were analyzed by molecular typing using PCR-based methods: spacer-oligonucleotide typing (spoligotyping), Beijing family-specific PCR (detection of the deletion of region of difference 105 [RD105]), and mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) analysis. Different combinations of MIRU-VNTR loci were evaluated to define the genotypes and clustering characteristics of the local strains. We found that Beijing family strains represented 89.5% of the isolates studied. However, the rates of multidrug-resistant (MDR) M. tuberculosis among Beijing and non-Beijing family strains were not statistically different. The 15-locus set is considered the optimal MIRU-VNTR locus combination for analyzing the M. tuberculosis strains epidemic in this area, while the 10-locus set is an ideal set for first-line molecular typing. We found that the clustering rate of all the M. tuberculosis isolates analyzed was 10.0% using the 15-locus set typing. We conclude that the Beijing family genotype is predominant and that highly epidemic TB and MDR TB are less likely associated with the active transmission of M. tuberculosis in the study area.