79株结核分枝杆菌临床分离株吡嗪酰胺耐药基因pncA突变分析

Analysis of mutations of pyrazinamide-resistant gene pncA in 79 Mycobacterium tuberculosis clinical isolates

目的了解结核分枝杆菌临床分离株pnc A基因突变情况,研究吡嗪酰胺耐药与北京基因型以及pnc A基因突变之间的关系。方法对79株结核分枝杆菌临床分离株进行MGIT 960吡嗪酰胺药敏试验,北京基因型的鉴定,pnc A基因扩增和测序。结果 79株临床分离株中,吡嗪酰胺耐药39株,吡嗪酰胺敏感40株。北京基因型在PZA耐药株、PZA敏感株中的比例分别为94.9%(37/39)、92.5%(37/40),差异无统计学意义(χ2=0.22,P=0.64)。40株吡嗪酰胺敏感株均未发生pnc A基因突变,39株吡嗪酰胺耐药株中有31株发生突变,突变率为79.5%(31/39)。耐药株中的pnc A基因突变率高于敏感株,差异有统计学意义(χ2=52.33,P=0.00)。吡嗪酰胺耐药株中共发现26种突变类型。结论结核分枝杆菌耐吡嗪酰胺主要机制之一为pnc A基因突变。北京基因型可能与吡嗪酰胺耐药无关。

Objective To understand the mutations of pnc A gene in Mycobacterium tuberculosis（ M. tuberculosis） clinical isolates,and to study the relationship between pyrazinamide resistance and Beijing genotype or the mutations of pnc A gene. Methods 79 M. tuberculosis clinical isolates were tested for pyrazinamide sensitivity by MGIT 960 system,Beijing genotype and application and sequencing of pnc A gene. Results From 79 M. tuberculosis clinical isolates,39 isolates were pyrazinamide- resistant,and the other 40 strains were pyrazinamide- susceptible. The proportion of Beijing genotype in PZA resistant strains,PZA susceptible strains were respectively 94. 9%（ 37 /39）,92. 5%（ 37 /40）,the difference was no statistical significance（ χ2= 0. 22,P = 0. 64）. No mutations of pnc A gene was detected in 40 pyrazinamide- susceptible isolates. In 39 pyrazinamide-resistant isolates,there were 31 strains mutated,and the mutation rate of pnc A gene was 79. 5%（ 31 /39）. The mutation rate of pnc A gene in the resistant strains was higher than that in the susceptible strains,and the difference had statistical significance（ χ2= 52. 33,P = 0. 00）. 26 kinds of mutations of pnc A gene were detected from the pyrazinamide- resistant strains. Conclusion Mutation of pnc A gene may be one of the major molecular mechanisms of pyrazinamide resistance. The Beijing genotype may have no relationship with pyrazinamide resistance.