肺炎链球菌pbp2B基因突变与β-内酰胺类抗生素耐药相关性的研究

Determination of correlation between mutation in pbp2B gene and resistance to β-lactam antibiotics of Streptococcus pneumoniae

目的:探讨肺炎链球菌临床菌株pbp2B基因突变与β-内酰胺类抗生素耐药的相关性。方法:采用二倍微量稀释法检测23株肺炎链球菌临床菌株对5种β-内酰胺类抗生素的最低抑菌浓度(MIC)。采用PCR扩增pbp2B基因片段,T-A克隆后测序。根据药敏试验及测序结果,分析pbp2B基因片段突变与β-内酰胺类抗生素耐药的相关性。结果:43.5%(10/23)肺炎链球菌临床菌株对5种β-内酰胺类抗生素敏感,其余56.5%(13/23)菌株耐药,其中有两株高度耐药。β-内酰胺类抗生素敏感菌株pbp2B基因片段仅有2个氨基酸发生变异,且不位于162～206和215～265区域。对β-内酰胺类抗生素低、中水平耐药菌株仅在pbp2B基因片段162～206区域出现氨基酸突变,162～206和215～265区域均有氨基酸突变的菌株对β-内酰胺类抗生素高度耐药。结论:本地区肺炎链球菌临床菌株对β-内酰胺类抗生素有很高的耐药率。肺炎链球菌pbp2B基因片段162～206区域突变仅引起低、中水平β-内酰胺类抗生素耐药性,高度耐药性则与215～265区域突变密切相关。

Objective：To determine the correlation between mutation in pbp2B gene and resistance to β-lactam antibiotics of Streptococcus pneumoniae.Methods：Double microdilution method was used to detect the minimal inhibitory concentration（MIC） of fiveβ-lactam antibiotics against 23 isolates of Streptococcus pneumoniae.The pbp2B gene segments in isolates were amplified by PCR and then sequenced after T-A cloning.According to the results of drug sensitive test and sequencing,the correlation between pbp2B gene mutation and β-lactam antibiotics resistance was analyzed.Results：43.5%（10/23） of the isolates were sensitive to all the β-lactam antibiotics,while 56.5%（13/23） of the isolates were resistant to these antibiotics in which two isolates showed high drug resistance.The β-lactam antibiotics-sensitive strains only presented the mutation of two amino acid residuals that located outside of both 162～206 and 215～265 regions.The low and moderate β-lactam antibiotics-resistant strains displayed amino acid residual mutation in 162～206 region of pbp2B gene segment alone.The strains with mino acid residual mutation in both the 162～206 and 215～265 regions of pbp2B gene segment were highly resistant to β-lactam antibiotics.Conclusion：There is a high β-lactam antibiotics-resistant frequency of Streptococcus pneumoniae isolates in the area.The mutation in 162-206 region of pbp2B gene of Streptococcus pneumoniae only causes low and moderate β-lactam antibiotics resistance,while the mutation in both 162-206 and 215-265 regions of pbp2B gene are closely associated with high β-lactam antibiotics resistance.