ABSTRACT
Objective To characterize the relationship between such phenotypes and the patterns of genetic mutations in the corresponding resistance genes in drug-resistant Mycobacterium tuberculosis (MTB)isolates in Shenzhen of China during 2007-2008.Methods According to standard of WHO,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,rrs1,gyrAB,rrs2)in these MTB isolates were identified by PCR,followed by DNA sequencing of the purified PCR products.The minimal inhibitory concentration(MIC)values of the aforementioned anti-tuberculosis drugs were determined for these MTB clinical isolates by two-fold dilution method in vitro.Results A total of 123 isolates were collected,73 isolates were drug resistant.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 84.6%,93.6%,65.9%,100%,61.1%.For katG gene,the mutation detected were S315T or S315N.For rpoB,the most frequently found changes were S531L(30/44,68.2%)and H526D(9/44,20.5%)or H526R(1/44,2.3%).The reported mutations that K43R and KS8Q were founded in the rpsL locus and 491C→T and 513A→C were founded in the rrs1 gene related with streptomycin-resistant strains.For gyrA,all gyrA mutations were clustered in codons 90,91,and 94 apart from the S95T that was natural polymorphism.accounted for 81.1% of the ofloxacin-resistant isolates,and condon 91 was the most frequently mutated.No mutation were found in gyrB.The most frequent substitution were 1400 A→G(9/11,81.8%)and 1483 G→T(2/11,18.2%)in a specific region of the rrs2 gene related with kanamycin-resistant strains.No mutations except S95T of gyrA detected in the drug-susceptible isolates.The MIC values of clinical drug-resistant strains that the same drug-resistant group contains a different resistance phenotype are basically the same with the relevant resistance genes in the same mutation.Associated resistance mutations in different sites varied significantly with their MIC values.Conclusion The mutation characterization of drug-resistant and drug-suscep-tible isolates of MTB have been shown to vary according to geographic region,phenotypic characteristics exist difference in resistance levels due to different muntants of drug-resistant gene.
ABSTRACT
OBJECTIVE:To evaluate the initial and acquired resistance level of lung tuberculosis in Shenzhen.METHODS:Culture-positive of sputum specimens of1948cases of lung tuberculosis were collected in Shenzhen from1999to2002and the resistance of tubercle bacillus in sputum-positive to four anti-tuberculosis drugs(isonicotinylhydrazide INH,streptomycin SM,rifampin RFP,Ethambutol EMB)were tested by WHO guideline.RESULTS:The total rate of tubercle bacillus to drug resistance was35.06%,initial drug resistance rate34.01%,initial multi-drug resistance rate4.97%,acquired re?sistance rate45.51%,and acquired multi-drug resistance rate12.92%.Acquired resistance rate of tubercle bacillus to each of4drugs was on the rise to different extents as compared with initial resistance rate.The rise was39.91%for SM,94.07%for INH,44.04%for EMB,and118.18%for RFP.CONCLUSIONS:The initial drug resistance rate ranks higher in Shenzhen as compared with the average level in the whole nation,resistance rates of RFP and INH double after combined administration.