Abstract:

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.

Key words: Bordetella pertussis, virulence-related gene, antimicrobial susceptibility

摘要：

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23S rDNA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23S rDNA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0.004～0.500 mg/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。

关键词: 百日咳鲍特菌, 毒力基因, 抗菌药物敏感性