Fatal case of macrolide-resistant Bordetella pertussis infection, Japan, 2024.

Here, we present a fatal case of macrolide-resistant Bordetella pertussis (MRBP) infection in a 1-month-old female infant born prematurely at 34 weeks of gestation. The infant, unvaccinated against pertussis, exhibited respiratory failure, bilateral pneumonia, and hyperleukocytosis (109.8 × 109/L) on day 44 of life. Despite initial treatment with azithromycin and a high-flow nasal cannula, her condition deteriorated rapidly, requiring mechanical ventilation and venoarterial extracorporeal membrane oxygenation. The infant passed away four days after symptom onset. Nasopharyngeal swabs confirmed the presence of B. pertussis carrying an A2047G mutation in the 23S rRNA gene, resulting in significant macrolide resistance. Phylogenetic analysis indicated that the isolate was genetically closer to Chinese MT28-MRBP isolates than to previously identified Japanese isolates. The combination of early infancy and delayed administration of effective antimicrobials likely contributed to the unfavorable outcome in this case. It is imperative to monitor the global dissemination of MRBPs and enhance local diagnostic capabilities.