murM基因变异与肺炎链球菌青霉素高度耐药及头孢曲松耐药的相关性

Alterations of murM gene and high-level penicillin-resistant as well as ceftriaxone resistance of Streptococcus pneumoniae

目的 研究肺炎链球菌murM基因变异与青霉素及头孢曲松耐药的相关性。方法 应用PCR技术扩增肺炎链球菌murM基因并进行基因测序。选取肺炎链球菌株 5 5株 ,包括青霉素敏感株 10株 (MIC≤ 0 .0 6 μg/ml) ;青霉素耐药株 4 5株 ,其中低水平耐药 10株 (MIC 0 .12～ 1μg /ml) ,高水平耐药 35株 (MIC≥ 2 μg/ml) ,在青霉素高水平耐药菌株中 ,对头孢曲松耐药 13株 (MIC≥ 2 μg/ml)。用敏感株R36AmurM基因序列作为比较标准。结果 5 5株肺炎链球菌murM基因PCR产物测序结果 ,16株murM基因发生显著变异 (变异率≥ 3% ) ,1株青霉素MIC 3μg/ml、头孢曲松MIC 2 μg/ml的菌株 ,其murM基因变异率 3.4 % ;15株青霉素MIC≥ 8μg/ml或头孢曲松MIC≥ 2 μg/ml的菌株 ,murM基因变异率达 10 % ,呈嵌合式变异。murM基因变异与肺炎链球菌青霉素及头孢曲松MIC显著相关 (χ2 =36 .5 32 ,P <0 .0 1;χ2 =37.116 ,P <0 .0 1)。结论 肺炎链球菌murM基因变异与青霉素高度耐药 (MIC≥8μg/ml)及头孢曲松耐药 (MIC≥ 2 μg/ml)有显著的相关性。

Objective To investigate the correlation between the variation of murM gene and penicillin-resistant and ceftriaxone resistance of Streptococcus pneumoniae. Methods To amplify murM gene from chromosomal DNA of Streptococcus pneumoniae isolates by PCR and then sequenced. Fifty-five strains of Streptococcus pneumoniae were chosen, containing 10 penicillin-susceptible strains (MIC≤0.06μg/ml), 10 low-level penicillin-resistant strains (MIC 0.12-1μg/ml), 35 high-level penicillin-resistant strains(MIC≥2μg/ml), 13 of those were resistant to ceftriaxone (MIC≥2μg/ml). The nucleotide sequence of the murM gene from susceptible strain R36A was used as the control for comparison. Results There were 16 strains in which the sequence of murM gene showed a striking divergence. One strain(penicillin MIC 3μg/ml, ceftriaxone MIC≥2μg/ml)revealed 3.4% nucleotide sequence divergence from the strain R36A. Fifteen strains revealed 10% nucleotide sequence divergence, in which penicillin MIC≥8μg/ml and/or ceftriaxone MIC≥2μg/ml. The variations of murM genes displayed a mosaic pattern. The variation of murM gene was closely associated with penicillin MIC and ceftriaxone MIC (χ2= 36.532, P<0.01; χ2=37.116, P<0.01). Conclusion High-level penicillin resistance and ceftriaxone resistance of Streptococcus pneumoniae were significantly correlated with mutation of murM gene.