[Antimicrobial susceptibility and antigen genotypes of Bordetella pertussis strains isolated from neonates].

OBJECTIVE

To investigate the alternative antimicrobial drugs for the treatment of neonatal pertussis and the antigen genotypes of Bordetella pertussis (B. pertussis) strains.

METHODS

A total of 32 B. pertussis strains isolated from neonates between May 2013 and July 2018 were used in this study. E-test stripes were used to measure the minimal inhibitory concentration (MIC) of 18 antimicrobial drugs including erythromycin, sulfamethoxazole-trimethoprim (SMZ) and ampicillin. The 23S rRNA gene of isolated strains was amplified and sequenced to identify the mutation site of erythromycin resistance gene, and the seven antigen genotypes of B. pertussis strains (ptxA, ptxC, ptxP, prn, fim2, fim3 and tcfA2) were analyzed.

RESULTS

Of the 32 B. pertussis strains, 25 (78%) were resistant to erythromycin, azithromycin, clarithromycin and clindamycin, with an MIC of >256 mg/L, and A2047G mutation was observed in the 23S rRNA gene. All strains had an MIC of ≤0.064 mg/L for SMZ. The MIC of ampicillin, amoxicillin, amoxicillin-clavulanic acid and ceftriaxone ranged from 0.032 to 1 mg/L. The strains resistant to macrolide antibiotics had an antigen genotype of ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2.

CONCLUSIONS

B. pertussis strains from neonates are often resistant to macrolides, and the in vitro test shows that off-label use of sulfonamides is a reliable regimen for the treatment of neonates with macrolide-resistant pertussis. The prevalence of drug-resistant strains further emphasizes the importance of immunoprophylaxis.