Cui Zhen-ling, Wang Xiao-li, Wang Jie, Lu Jun-mei, Hu Zhong-yi
Shanghai Key Laboratory of Tuberculosis, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai 200433, China.
Zhonghua Jie He He Hu Xi Za Zhi. 2010 Jul;33(7):505-9.
To explore the effects of 2 major drug-resistant mechanisms in clinically isolated strains of extensively drug-resistant tuberculosis (XDR-MTB).
Genomic DNA of 10 XDR-MTB strains isolated from Shanghai Pulmonary Hospital were extracted. The main gene mutations related to drug resistance and 15 SNPs unique to XDR-MTB clinical isolate KZN605 reported by the Broad Institute in USA were detected by sequencing. The changes of minimal inhibition concentration (MIC) of XDR-MTB isolates were detected before and after the addition of efflux pump inhibitors verapamil, CCCP and reserpine in liquid cultures.
The mutation of rpoB, katG and rpsL occurred in all XDR-MTB strains. The mutation of gyrA, gyrB and rrs occurred in 9 strains, 2 strains and 6 strains respectively. There was no mutation of tlyA in all the strains. Most of the SNPs in KZN 605 strains were not detected in the clinical strains. The clinical strains showed no significant changes of MICs, except 1 strain for which the MIC of ofloxacin decreased by 16 times after addition of the efflux pump inhibitors.
The gene mutations related to drug resistance are the key mechanism for the clinical XDR-MTB strains, while the efflux pumps partly play a role in the drug resistance to fluoroquinolones. The detailed mechanism of efflux pump mediated drug resistance to other anti-TB drugs needs further study.
探讨广泛耐药结核病（XDR-MTB）临床分离株中2种主要耐药机制的作用。
提取自上海肺科医院分离的10株XDR-MTB菌株的基因组DNA。通过测序检测与耐药相关的主要基因突变以及美国布罗德研究所报道的XDR-MTB临床分离株KZN605特有的15个单核苷酸多态性（SNP）。在液体培养中加入外排泵抑制剂维拉帕米、碳酰氰间氯苯腙（CCCP）和利血平前后，检测XDR-MTB分离株最低抑菌浓度（MIC）的变化。
所有XDR-MTB菌株均发生rpoB、katG和rpsL基因突变。gyrA、gyrB和rrs基因突变分别发生在9株、2株和6株菌株中。所有菌株均未发生tlyA基因突变。KZN605菌株中的大多数SNP在临床菌株中未检测到。临床菌株的MICs无显著变化，仅1株菌株在加入外排泵抑制剂后氧氟沙星MIC下降16倍。
与耐药相关的基因突变是临床XDR-MTB菌株的关键耐药机制，而外排泵在对氟喹诺酮类药物的耐药中部分起作用。外排泵介导对其他抗结核药物耐药的详细机制有待进一步研究。
