# Analysis of Macrolide Resistance in Bordetella pertussis Isolated from Japanese Children in 2025 Using Test Kit and Sequence Method

## TL;DR

This study found high rates of macrolide-resistant Bordetella pertussis in Japanese children post-pandemic, highlighting the need for ongoing surveillance and alternative detection methods.

## Contribution

The study reports a high prevalence of macrolide resistance in B. pertussis isolates from Japanese children using both test kits and sequencing.

## Key findings

- 82.7% of sequenced B. pertussis isolates had the A2047G mutation linked to macrolide resistance.
- Resistance rates varied widely between clinics, ranging from 40% to 96%.
- Repurposing residual clinical samples proved useful for resistance surveillance due to detection challenges.

## Abstract

Background: Bordetella pertussis causes pertussis, a respiratory infection with whooping cough. Despite a high vaccine coverage, pertussis resurged post-COVID-19 pandemic. Meanwhile, isolates resistant to macrolides—the first-line therapy—have increased in several countries, including Japan. Culturing B. pertussis and detecting resistance are difficult; reports remain limited in Japan. Methods: From March to August 2025, we collected nasopharyngeal samples from children aged 0–15 years with suspected pertussis at six Japanese clinics. Pediatricians obtained swabs and tested them using gene-amplification kits (e.g., BioFire® SpotFire® in four clinics, LAMP Pertussis Detection® in two clinics). B. pertussis was confirmed by PCR; isolates were sequenced to identify macrolide-resistant mutations. Results: Samples were taken from 54 children, the number of boys and girls was 34 and 20, and their median age was 12 years old. Among 54 B. pertussis isolates, 43/52 (82.7%) sequenced strains harbored the A2047G mutation associated with macrolide resistance. Resistance rates at each clinic varied from 40% to 96%. Conclusions: These findings indicate a post-pandemic rise in macrolide-resistant B. pertussis in Japan. Ongoing resistance surveillance is essential, and repurposing residual clinical samples after routine testing is useful given culture and detection challenges.