肺炎链球菌青霉素结合蛋白基因多态性与其青霉素敏感性的关系

The relationship between penicillin-binding protein genes restriction polymorphism and penicillin susceptibility in Streptococcus pneumoniae

目的探讨肺炎链球菌青霉素结合蛋白基因(pbps)多态性与青霉素敏感性的关系。方法以包括63株青霉素不敏感肺炎链球菌(PNSP)和69株青霉素敏感菌(PSSP)共132株菌为研究对象,浓度梯度(E-test)法检测青霉素最低抑菌浓度(MIC),PCR法扩增pbp2b、pbp2x和pbp1a,分析其限制性片段长度多态性(RFLP)。结果pbp1a有9种型,其中两种见于PSSP和部分PNSP菌株,其他7种主要见于青霉素MIC值≥0·25μg/ml的菌株(21/22)。pbp2b有10种型,其中3种型见于PSSP和部分PNSP菌株,其他7种主要见于青霉素MIC≥0·25μg/ml的菌株(20/22)。pbp2x谱型31个,PSSP菌株中有17种,其中13种仅见于PSSP菌株;余下14种只存在于PNSP(35株)。pbp1a、pbp2b和pbp2x组合的pbps型共47种,PSSP菌株中23种,其中17种仅存在于PSSP;其他24种仅见于PNSP(36株)。根据pbp1a或pbp2b基因型判断青霉素敏感,虽然敏感度高,但特异度较低(<50%),准确性也较低;根据pbp2x或pbps基因型判断,敏感度、特异度和准确性均在85%以上。结论肺炎链球菌青霉素耐药主要与PBP1a、PBP2b和PBP2x变异有关;根据肺炎链球菌pbps基因多态性,可快速准确地判断其青霉素敏感性。

Objective To indicate the restriction profiles of pbps in Streptococcus pneumoniae （S. pneumoniae）, and relationship between pbps profiles and the penicillin MIC. Methods The E-test MIC method was used to determinate penicillin susceptibility of 132 S. pneumoniae strains consisting of 69 penicillin susceptible S. pneumoniae （PSSP） strains and 63 nonsusceptible S. pneumoniae （PNSP） strains. Furthermore, we compared these strains by detecting restriction fragment length polymorphism （RFLP） of the PBPs genes pbpla, pbp2b and pbp2x. Results The RFLP results showed that 9 genotypes were founded for pbpla, in which 2 were detected from PSSP and some PNSP strains. The other 7 ones were founded mainly in the PNSP with penicillin MIC≥0. 25 μg/ml. Ten genotypes were founded for pbp2b, in which 3 were detected from PSSP and some PNSP strains. The other 7 ones, similar with pbpla, were founded mainly in the PNSP with penicillin MIC ≥ 0. 25 μg/ml. Thirty-one restrictive patterns were founded for pbp2x. Seventeen pattemss from them were detected in PSSP, and 13 ones were founded only in PSSP. The other 14 patterns all were covered PNSP strains. A total of 47 patterns were found according to the three pbps types. Twenty-three patterns from them were detected in PSSP, and 17 ones were founded only in PSSP. The other 24 patterns all were detected in PNSP. Conclusions Results of the study are consistent with the concept that mutations in PBP1 a, PBP2b and PBP2x play an important role in the development of resistance to β-1actam antibiotics by S. pneumoniae. In the meantime, the profiles of pbps can predict penicillin susceptibility.