Objective:

To characterize admission-time molecular load–antibody titer patterns in children with Mycoplasma pneumoniae pneumonia (MPP) and describe pathogen co-detection profiles.

Approach:

• Study Design: Retrospective cohort study of hospitalized children with tNGS-confirmed MPP from January to December 2024.
• Data Analysis: Co-detection profiles and clinical characteristics were summarized for the full cohort; load–titer phenotyping was performed using 2D-KDE for children with MP-only pneumonia.

Key Findings:

• Among 402 children, 39.3% had MP-only pneumonia, 30.1% had MP + viral co-detection, and 30.6% had MP + bacterial co-detection.
• MP + viral co-detection was linked to younger age, longer cough duration, higher WBC and platelet counts, lower CRP, and higher antibody titers.
• Three admission-time molecular–serologic patterns were identified in MP-only pneumonia: high-load/seronegative, high-load/high-titer, and lower-load/high-titer.

Interpretation:

The study suggests that persistent MP molecular signal and established humoral response may coexist at hospitalization, providing a framework for understanding MP tNGS signals in relation to immune status and illness timing.

Limitations:

• The study was limited to a single tertiary care center, which may affect generalizability.
• The retrospective design may introduce biases related to data collection and interpretation.

Conclusion:

Admission-time molecular load–antibody titer phenotyping in children with MP-only pneumonia revealed distinct immunologic patterns.