Macrolide Resistance and P1 Cytadhesin Genotyping of Mycoplasma pneumoniae during Outbreak - Canada, 2024–2025

Q: What was investigated in this study of Mycoplasma pneumoniae during the 2024–2025 outbreak?

The study examined macrolide resistance and P1 cytadhesin genotypes of M. pneumoniae in Hamilton, Ontario during 2024–2025.

Q: How was macrolide resistance assessed?

Macrolide resistance was screened using PCR genotyping, and the resistance-associated SNP identified was A2063G (linked to high-level macrolide resistance).

Q: Did P1 genotype types differ in macrolide resistance rates?

Yes. The P1-1 type showed a significantly higher macrolide resistance rate (29.9%) than the P1-2 type (7.7%).

Sep 30, 2026

Uploaded by SANS

Investigation of Mycoplasma pneumoniae during the 2024–2025 outbreak in Hamilton, Ontario, Canada assessed macrolide resistance and P1 cytadhesin genotypes. Macrolide resistance remained stable at about 10%–20%, while meaningful shifts occurred in P1 genotype distribution and resistance rates across P1 types, indicating changing molecular epidemiology in Ontario since 2011–2012. Using laboratory-developed PCR on nasopharyngeal specimens, the study linked resistance to the A2063G SNP and evaluated differences in positivity and resistance by age and by prepandemic versus postpandemic periods.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

The outbreak and study scope

Specimen testing and laboratory methods

Detection and resistance patterns

Positivity trends and monthly variation

Age-related differences

Genotype distribution and comparisons

P1-1 vs P1-2 resistance rates

Prepandemic vs postpandemic comparison

DISPATCHES Macrolide Resistance and P1 Cytadhesin Genotyping of Mycoplasma pneumoniae during Outbreak, Canada, 2024–2025 Zareen Fatima,1 Padman Jayaratne,1 Amjad Arrabi, Candy Rutherford, Daniela Leto, Marek Smieja, Mohammad Rubayet Hasan We investigated macrolide resistance and P1 genotypes of Mycoplasma pneumoniae during the 2024–2025 outbreak in Hamilton, Ontario, Canada. Macrolide resistance remained stable at ≈ 10%–20%, but significant shifts in P1 genotype distribution and resistance rates in P1 types occurred, indicating notable changes in M. pneumoniae molecular epidemiology in Ontario since 2011–2012. Mycoplowarsmreasppineumoratoryniaetracits ianfcauseectionso, fupppartiecrulanarldyin children, and occurs in endemic and epidemic patterns. Although tracheobronchitis is common, pneumonia is the most clinically significant manifestation, accounting for ≈4%–8% of community-acquired bacterial pneumonias during endemic periods (1) . Macrolides remain the primary therapy for M. pneumoniae, but the global rise in clinically relevant resistance is posing increasing challenges to treatment (2) . Since COVID-19 pandemic restrictions were scaled back during 2023, M. pneumoniae incidence and outbreaks have increased substantially worldwide (3–5) . In Ontario, Canada, a delayed but unprecedented rise in detection, reaching up to 30% positivity, has been reported since May 2024 (6) . We assessed macrolide resistance rates and P1 cytadhesin types of M. pneumoniae during the 2024–2025 outbreak in Hamilton, Ontario, Canada, and compared them with strains collected before the COVID-19 pandemic. Author affiliations: McMaster University, Hamilton, Ontario, Canada (Z. Fatima, P. Jayaratne, D. Leto, M. Smieja, M. R. Hasan); Research Institute of St. Joe’s Hamilton, Hamilton (Z. Fatima, A. Arrabi, M. Smieja, M. R. Hasan); Hamilton Regional Laboratory Medicine Program, Hamilton (P. Jayaratne, C. Rutherford, D. Leto, M. Smieja, M. R. Hasan) DOI: [https://doi.org/10.3201/eid3112.250872](https://doi.org/10.3201/eid3112.250872) The Study During January 2024–April 2025, a total of 4,297 nasopharyngeal swab (NPS) specimens from 3,717 patients were received by the Microbiology Laboratory of the Hamilton Regional Laboratory Medicine Program in Hamilton for M. pneumoniae detection by a laboratory-developed PCR. We screened all M. pneumoniae–positive samples (n = 417 after removing duplicates) for macrolide resistance by PCR genotyping and performed P1 cytadhesin typing on a randomly selected ≈25% subset of positive specimens from each month (n = 110) by amplifying the RepMP4 region of P1 cytadhesin gene ( 7) and sequencing with nanopore technology (Oxford Nanopore, [https://](https://)[ ](https://)[nanoporetech.com](nanoporetech.com)) (Appendix, [https://wwwnc.cdc](https://wwwnc.cdc). gov/EID/article/31/12/25-0872-App1.pdf) . In addition to specimens received during the postpandemic period, additional M. pneumoniae–positive samples received during 2013–2020 were tested for macrolide resistance (n = 45) and P1 types (n = 23) . We assessed statistical significance of differences in M. pneumoniae detection rates and macrolide resistance among different patient groups using the χ2 test with Yates cor rection to adjust for small sample size (Appendix) . On average, 14.2%(381/2,680) of patients tested positive for M. pneumoniae in 2024, compared with 0.34%(2/576) in 2022 and 0.36%(2/555) in 2023. Since May 2024, the positivity rate gradually increased, reaching a peak of 22.5% in September 2024. After September, positivity rates steadily declined to <5% by January 2025, despite increased testing volumes through December 2024. Macrolide resistance rates varied by month and accounted for 11.8% of all positive samples during January 2024–April 2025; the highest rate of resistance (50%) was noted in July 2024 (Figure 1, panel 1These first authors contributed equally to this article. 2316 Emerging Infectious Diseases • [www.cdc.gov/eid]

FAQs

What was investigated in this study of Mycoplasma pneumoniae during the 2024–2025 outbreak?

The study examined macrolide resistance and P1 cytadhesin genotypes of M. pneumoniae in Hamilton, Ontario during 2024–2025.

How was macrolide resistance assessed?

Macrolide resistance was screened using PCR genotyping, and the resistance-associated SNP identified was A2063G (linked to high-level macrolide resistance).

Did P1 genotype types differ in macrolide resistance rates?

Yes. The P1-1 type showed a significantly higher macrolide resistance rate (29.9%) than the P1-2 type (7.7%).

Sep 30, 2026

Uploaded by SANS