百日咳致病菌株的药物敏感性和疫苗相关基因型研究

Distribution of vaccine-related genotypes and antimicrobial susceptibility among the Bordetella pertussis isolates

目的了解百日咳确诊患儿的临床特征、致病菌株的毒力基因分型及抗菌药物敏感性状况。方法收集2015—2016年首都医科大学附属北京儿童医院细菌培养确诊的224例百日咳患儿的临床信息,采用E-test法及KB纸片法检测分离的百日咳鲍特菌对抗菌药物的敏感性,并检测菌株的23SrDNA基因耐药突变及其抗原基因型。结果224例患儿分别来自全国14个省份,其中150例(67.0%)患儿<6月龄,176例(78.6%)例患儿未接种或未完成全程百日咳疫苗接种。224株百日咳鲍特菌的主要抗原基因型为ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2,占90.6%(203/224)。所有红霉素耐药菌株均为ptxP1基因型,且23SrDNA基因均检测到A2047G位点突变。分离到18株ptxP3基因型高毒力株,对大环内酯类药物均敏感。全部分离株对磺胺甲基异噁唑/甲氧苄啶(SMZ)最小抑菌浓度(MIC)值分布范围为0.004~0.500mg/L。结论当前培养确诊的百日咳患儿以未接种疫苗的小婴儿为主,致病菌株的抗原基因型主要为ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2,该型菌株普遍对大环内酯类耐药。高毒力的ptxP3型致病菌株较少见,均对大环内酯类敏感。体外药物敏感性试验提示SMZ可用于百日咳的经验治疗。

Objective To summarize the clinical characteristics of children with pertussis and investigate the distribution of virulence-related genotypes and antimicrobial susceptibility among the Bordetella pertussis isolates.Methods The clinical information of 224 culture-positive pertussis cases in Beijing Children’s Hospital,Capital Medical University from 2015 to 2016 was collected.Antimicrobial susceptibility was determined by E-test and Kirby-Bauer(KB)disk diffusion methods.A fragment of the 23S rDNA genes was detected for drug-resistance mutation and antigen genotypes. Results The 224 culture-positive pertussis cases were from 14 provinces or municipalities.Among the 224 subjects,150 patients(67.0%)were younger than 6 months old and 176 patients(78.6%)were unvaccinated or not fully vaccinated individuals.The commonest virulence-associated genotype was ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2,with frequencies of 90.6%(203/224).All erythromycin-resistant strains were determined A2047G mutation in 23S rDNA sequences,and the strains were the ptxP1 genotype(203/224).Eighteen ptxP3 strains were identified in the present study and all ptxP3 strains were sensitive to erythromycin.All isolates were determined low MIC against sulphamethoxazole/trimethoprim(0.004- 0.500 mg/L).Conclusion The culture-positive pertussis cases are mostly infants and young children unvaccinated or not-fully vaccinated.The isolates genotyped as ptxA1/ptxC1/ ptxP1/prn1/fim2-1/fim3-1/tcfA2 are widespread,which are highly resistant to erythromycin.The high-virulent strains harboring ptxP3 are rare,and are sensitive to erythromycin.Sulphamethoxazole/trimethoprim is effective to treat pertussis caused by erythromycin-resistant isolates.