50株肺炎链球菌pbp2B基因突变与苯唑西林药敏相关性分析

Relationship of the Mutation pbp2B Genes with Oxacillin Susceptibility among 50 Isolates of Streptococcus pneumoniae

目的 探讨我国耐青霉素肺炎链球菌 (Streptococcuspneumoniae,SPN)pbp2B基因的突变与苯唑西林药敏表型相关性。方法 对呼吸道感染患儿痰标本中分离到的 5 0株肺炎链球菌 ,用K B法进行苯唑西林药物敏感试验 ,用套式聚合酶链反应 (nPCR)扩增pbp2B基因 ,对PCR产物直接进行DNA测序 ,测得序列与SPNR6株 (青霉素敏感株 )序列 [GenBank登录号 :NC 0 0 30 98]相比较。结果 2 9株无突变 ,2 1株有突变 ;突变的 2 1株中 2 0株为点突变 ,可分A、B、C、D 4个类型 ,分别占 71 4 %、14 3%、4 8%、4 8% ;另 1株为E型 ,除有点突变外 ,并有CCT碱基插入 ;无突变的 2 9株SPN菌中苯唑西林敏感率为 86 2 % ;有突变的 2 1株中苯唑西林敏感率为 9 5 % ,二者相比较差异有显著性 (P <0 0 0 1) ;5种突变类型均存在SPN菌对苯唑西林耐药。结论 SPN分离株pbp2B基因突变与其苯唑西林耐药性相关 。

OBJECTIVE To investigate the relationship of the mutation pbp2B genes with oxacillin susceptibility among 50 isolates of Streptococcus pneumoniae. METHODS (1)Fifty pneumococcal isolates were from respiratory tract secretions of children with respiratory diseases. (2)Oxacillin susceptibility was determined by using K B disk. (3) Detecting pbp2B genes of the isolates by nested PCR. (4)Sequencing the PCR productes. (5)Contrasting the DNA sequences of pneumococcal isolates with the DNA sequence of SPR6 [penicillin sensitive(www.ncbi. nlm. gov/nucleotide, NC 003098)]. RESULTS Of 50 isolates studied,the mutation of pbp2B gene was 42% (n=21) . Of 21 mutations,20 isolates had just point mutation and had A,B,C,D genotypies,1 isolate had both point mutation and adding CCT fragment E genotypy. A,B,C,D,E genotypies followed by 71 4%(n=15), 14 3%(n=3), 4 8%(n=1), 4 8%(n=1)and 4 8%(n=1). Of 29 non mutations,oxacillin susceptivity was 86 2%(n=25);of 21 mutations,oxacillin susceptivity was 9 5%(n=2);the both were much different (P<0 001) . All of five mutation genotypies come oxacillin resistance phenotypies. CONCLUSIONS Among pneumococcal isolates at our area, to bear a relation to the mutation pbp2B genes and oxacillin resistance;all of five mutation genotypies lead oxacillin resistance.