High prevalence of multidrug-resistant tuberculosis in Zunyi, Guizhou Province of China

Abstract

Sir, According to the WHO Report 2010, China had the most multidrug-resistant tuberculosis (MDR-TB) cases in 2008, followed by India and Russia, and was ranked 16th in terms of the estimated proportion of primary (5.7%) and acquired (previously treated) MDR-TB cases among the 27 MDR-TB highburden countries. However, our recent drug-susceptibility surveillance results indicated that the prevalence of acquired MDR-TB cases in the Zunyi area, Guizhou province, China, was much higher (45.1%) than the average prevalence of acquired MDR-TB in China (25.6%), but lower than those in the top six MDR-TB high-burden countries (Tajikistan, Kazakhstan, Azerbaijan, Republic of Moldova, Uzbekistan and Lithuania). To determine the prevalence and trends of drug-resistant TB in the Zunyi area, in order to improve the treatment outcomes of TB patients, 263 Mycobacterium tuberculosis clinical isolates were collected at the Affiliated Hospital of Zunyi Medical College from 2008 to 2010 and used in drug susceptibility testing against rifampicin, isoniazid, streptomycin and ethambutol. We used the proportion method on Lowenstein–Jensen media with different concentrations of drugs (rifampicin 40 mg/L, isoniazid 0.2 mg/L, streptomycin 4 mg/L and ethambutol 2 mg/L). The standard M. tuberculosis H37Rv strain was used as a control for all testing. To compare our results with those from other provinces of China, we selected recent survey results from Shanghai and 4 out of the 10 provinces (covering 38% of the total Chinese population) with the highest rates of MDR among new TB cases (5.4%–10.4%), and combined them with ours in Table 1. Results indicated that the Zunyi area had the highest prevalence of MDR-TB among previously treated (45.1%) and the second highest among new (8.1%) TB cases in China. In addition, it was observed that the proportions of rifampicin and isoniazid resistance in previously treated (56.0% versus 59.3%) and new (12.2% versus 14.5%) TB cases from the Zunyi area were similar (Table 1), which indicated that isoniazid resistance might be related to rifampicin resistance and that screening for rifampicin resistance could be used as a marker for the detection of MDR-TB. Since isoniazid has not been widely used as monotherapy for latent TB in China, this could explain the relative lack of single resistance to isoniazid in new TB cases observed in this study. It is obvious that percentages of TB cases with resistance to any of the four drugs in the Zunyi area were much higher than those from other provinces among previously treated TB cases (Table 1), suggesting that the Zunyi area of Guizhou province is one of the worst-affected areas in China and should be included in future surveillance of drug resistance in tuberculosis to better represent the prevalence of MDR-TB in China. To compare our results with those from other high-burden countries, such as India and Russia, we selectively included in Table 1 four studies with the highest proportions of MDR among previously treated patients (from 49% in Haryana to 38.2% in Rajasthan) out of the eight studies from India, five countries with the highest proportions of MDR among new TB cases (from 14.4% in Latvia to 4.0% in Ivanovo Oblast) from 35 countries that participated in the global surveillance (1994–97), and five countries with the highest proportions of MDR among new TB cases (from 22.3% in Azerbaijan to 14.8% in Uzbekistan) out of 83 countries/territories surveyed between 2002 and 2007. Comparison of the results shows that the Zunyi area of Guizhou Province, China, has the highest rate of TB cases resistant to ethambutol among previously treated patients (41.8%), and is one of the top 10 areas in the world in terms of the estimated proportion of MDR-TB cases among previously treated TB cases. Consequently, more surveillance should be conducted in the Zunyi area to monitor the trend of MDR-TB transmission, improve the treatment outcomes of TB patients and control the spread of drug-resistant TB, especially MDR-TB.