RESUMO
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 23 S 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 ptx A1/ptx C1/ptx P1/prn1/fim2-1/fim3-1/tcfA2,with frequencies of 90.6%(203/224). All erythromycin-resistant strains were determined A2047 G mutation in 23 S r DNA sequences,and the strains were the ptx P1 genotype(203/224). Eighteen ptx P3 strains were identified in the present study and all ptx P3 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 ptx A1/ptx C1/ptx P1/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.