[Molecular characterization of drug-resistant and extensive-drug resistant isolates of Mycobacterium tuberculosis in Shenzhen of China].

OBJECTIVE: To study the molecular characterization of drug-resistant and extensive-drug resistant isolates of Mycobacterium tuberculosis (MTB) in Shenzhen of China during 2007 - 2008. METHODS: According to the standards of WHO and International Union Against Tuberculosis and Lung Disease (IUATLD), 136 strains of MTB were collected by performing drug sensitivity test (DST) to isoniazid, rifampicin, streptomycin, ofloxacin and kanamycin on Lowenstein-Jensen in 1% proportion method. Genetic mutations in the corresponding resistance genes (rpoB, katG, rpsL, rrs((1)), gyrA/B, rrs((2))) in these MTB isolates were identified by PCR, followed by DNA sequencing of the purified PCR products. RESULTS: A total of 123 isolates were collected. Seventy-three isolates were drug resistant, and 50 isolates were drug susceptible. Among the isolates that were resistant to isoniazid, rifampicin, streptomycin, ofloxacin and kanamycin, the proportion of isolates that harboured mutations in the respective genes was 44/52, 44/47, 28/41, 11/11, and 11/18, respectively. For katG gene, the mutation detected was S315T or S315N. For rpoB, the most frequently found changes were S531L (30/44) and H526D (9/44) or H526R (1/44). For the reported mutations related with streptomycin-resistant strains, K43R and K88Q were found in the rpsL locus, and 491C-->T and 513A-->C were found in the rrs gene. For gyrA, all gyrA mutations were clustered in codons 90, 91, and 94 apart from the S95T that was natural polymorphism, accounting for 9/11 of the ofloxacin-resistant isolates, and condon 91 was the most frequently mutated. No mutations were found in gyrB. The most frequent substitutions were 1400A-->G (9/11) and 1483G-->T (2/11) in a specific region of the rrs gene related with kanamycin-resistant strains. No mutations except S95T of gyrA was detected in the drug- susceptible isolates. CONCLUSIONS: The mutation characterization of drug-resistant and drug- susceptible isolates of MTB was shown to vary according to geographic regions, and these findings can help understanding the molecular characterization and establishing a novel method for the detection of drug-resistant MTB.

[An epidemiological study on the ecological environment related to Nontuberculous mycobacteria in Shenzhen city of Guangdong province].

OBJECTIVE: To investigate the distribution of Nontuberculous mycobacteria in the environment of Shenzhen city and its related sensitivity to drugs. METHODS: 145 samples in the environment of Shenzhen city were collected and the samples were isolated, identified and its drug sensitivity were detected according to the "Procedure of Bacteriological Determination Regulation for Tuberculous Diagnosis", issued in 1995 by the Antituberculosis Association of China. RESULTS: All together, 53 strains of Mycobacteria were detected from the 145 sample, including 6 of them isolated from the polluted water in the hospital before disinfected, 4 from the polluted water in the hospital after disinfected, 4 from the dirt of air condition in the hospital, 34 from the polluted water in the residential area, 3 from the ocean water and 2 from the fountain. M. nonchromogenicum, M. avium, M. fortuitum, M. gordonae, M. genavense, M. chelonae and M. intracellulare were identified. CONCLUSION: Nontuberculous mycobacteria seemed to widely exist in the environment of Shenzhen city and the ratio of drug-resistant was high. Attention should be paid to the influence of Nontuberculous mycobacteria on humans in order to formulate effective control measure.