80株解脲脲原体的药敏及耐药机制分析

Antibiotic resistance and mechanism of 80 clinical strains of Ureaplasma urealyticm

目的 分析解脲脲原体(Ureaplasmaurealyticm ,Uu)的耐药情况,并探讨Uu可能的耐药机制。方法 对80株临床上分离到的Uu进行了药敏分析、PCR生物分群、tetM基因的检测和PCR扩增喹诺酮类药物耐药区(QRDR ,gyrA、gyrB、parC及parE)基因并分析其核苷酸序列。结果 80株临床分离的Uu有6 6份为生物1群,占82 .5 % ;对所测的9种药物全敏感的Uu比例仅为10 % (8 80 ) ;7株耐四环素Uu中有3株出现了tetM基因阳性条带;对6株临床分离Uu的QRDR(gyrA、gyrB、parC及parE)进行了突变分析,未发现环丙沙星、氧氟沙星均敏感Uu株有gyrA、gyrB、parC及parE突变,但耐喹诺酮Uu株有gyrA、parC和parE基因的点突变,并导致其编码的氨基酸改变。在这些QRDR的改变中,gyrA 137C→A和parC基因10 0C→T的误义突变导致其编码的相应氨基酸的改变,但parC基因的2 2 5G→A和parE基因4 0G→A ,4 1T→C的误义突变导致其编码的相应氨基酸的改变。对Uu耐药率及生物群分型结果进行分析发现,虽然两群Uu的耐药率不完全一样,但差异无统计学意义(P均>0 .0 5 )。结论 UuQRDR的改变是导致耐喹诺酮类药物的原因,单独parE基因突变引起其酶蛋白的氨基酸改变也可导致Uu耐喹诺酮类药物。

Objective To study the resistance mechanism of c linical isolates of Ureaplasma urealyticm(Uu). Methods A total of 80 clinical strains of Uu were collected in this study. Dru g sensitivity of Uu was tested by using mycoplasma IST 2, a product of bioMe rieux. The biotype of Uu and tetM gene were detected by PCR. The quinolo ne resistance determining region (QRDR) of 6 strains of Uu were amplified by PCR and sequenced by an ABI-Prism 377 sequencer. Results Only 10% of Uu was sensitive to all antibiotics tested and 82.5% was type Ⅰ. tetM gene was found in 3 strains of 7 tetracycline(TET) resistant Uu . Comparison between resistant isolates and reference strain ATCC700970 revealed that a C to A change at 137 nt of gyrA. QRDR led to the substitution of Asp 112 by glutamic acid; a C to T change at 100 nt and a G to A change at 225 nt of parC QRDR led to the substitution Ser83 by leucine and Ala125 by Thr respec tively; GT to AC change at 40-41 nt of parE QRDR led to the substitution Va l417 by Thr. No amino acid changes was identified in gyrB. Conclu sion The over use of fluoroquinolones had led to the emergence of qu inolone resistance in Uu. Topoisomerase Ⅳ as well as DNA gyrase is an impor tant target for fluoroquinolones in this microorganism. The results also suggest ed topoisomerase Ⅳ ParE subunit as potential targets in resistance to fluoroqui nolones.