青霉素不敏感的肺炎链球菌pbp2b基因新的变异

目的 调查本地区青霉素不敏感肺炎链球菌(PNSP)的pbp2b基因和氨基酸序列的变异特点.方法 2006年1-12月收集肺炎链球菌临床分离株24株,检测其对青霉素的敏感性,对青霉素不敏感肺炎链球菌的青霉素结合蛋白pbp2b基因进行PCR扩增和测序以及序列比对与生物信息学分析.结果 在13株青霉素不敏感肺炎链球菌[最低抑菌浓度(MIC)≥0.1 mg/L]中,均发生紧邻SSN的Thr445→,Ala替换以及Glu475→Gly、Thr488→Ala/ser的替换;而Glu332→Gly的替换也较常见,存在于12株PNSP(MIC≥0.25 mg/L);另外,在7株青霉素耐药的肺炎链球菌(MIC≥3 mg/L)中,均发生了紧邻KTG之后Ala618→Gly的替换,且这7株菌属于Back's Ⅱ群,与韩国菌株J77的核苷酸及氨基酸序列一致,而菌株14,15,8,11及24的氨基酸序列出现了新的变异,已向GenBank提交序列,获得序列号:EU035970,EU056919,EU056920,EU056921,EUl06886.结论 本地区大多数的青霉素耐药肺炎链球菌pbp2b基因的变异序列高度相似,而青霉素中度敏感肺炎链球菌的基因序列产生新的变异.

Novel gene sequence variants of pbp2b in penicillin-nonsusceptible Streptococcus pneumonia isolates

Objective To investigate the alternations in gene/amino acid sequence of penicillin-binding protein (PBP) 2b from clinical isolates of penicillin-nonsusceptible Streptococcus pneumonia(PNSP) in this region.Methods 24 strains of Streptococcus pneumonia were collected from January to December 2006.The antibiotics susceptibility of these strains was detected.PCR amplification and direct sequencing of pbp2b genes were performed.The sequence variations of PBP genes of the PNSP in this region were studied with sequence BLAST analysis.Results Three prominent substitutions were common tO 13 PNSP isolates with minimal inhibitory concentration(MIC) at least 0.1 mg/L.These included the replacement of Thr445→Ala following the conservative motif SSN,Glu475→Gly and Thr488→Ala/Ser.The exchange of Glu332→Gly was identified in 12 PNSP isolates of which the MIC was at least 0.25 mg/L.Seven penicillin resistant Streptococcus pneumonia (PRSP) isolates (MIC≥3 mg/L)shared the amino acid substitution Ala618→Gly adiacent to third conserved (KTG) motif and the PBP2b sequences of seven PRSP isolates were classified within Back's group Ⅱ and were very similar to those of the Korean J77 isolate.Novel gene and amino acid sequence variants in isolate 14,15,8,11 and 24 was identified in this study and these gene sequences have been deposited in the GenBank database and assigned accession no.EU035970,EU056919,EU056920,EU056921 and EU106886.Conclusion Analysis of pbp2b genes revealed highly similar patterns of nucleotide and amino acid sequence variation among most resistant isolates.while penicillin intermediate Streptococcus pneumonia might be associated with novel gene sequence variants.