Mycoplasma pneumoniae PCR positivity rate among children in Chengdu, China: a retrospective cross-sectional epidemiological study.

BACKGROUND

Mycoplasma pneumoniae (MP) is one of the most common pathogens responsible for respiratory infections in children. The objective of this study was to investigate MP positivity rate and its distribution characteristics across different clinical diagnostic groups among children in Chengdu, China.

METHODS

A retrospective cross-sectional study was conducted at a single center in Chengdu, China, involving children aged 0-18 years who underwent MP polymerase chain reaction (PCR) testing based on clinician requisition or self-requested laboratory testing (SRLT) between January 1 and December 31, 2024. χ2 tests and multivariable logistic regression models were applied for statistical analyses.

RESULTS

Among 94,889 children (51,105 males and 43,784 females), the overall MP positivity rate was 12.3%, with no significant difference between sexes. Across five clinical diagnostic groups, MP positivity rate was highest in the acute lower respiratory tract infections (ALRTIs) group (13.9%), followed by the SRLT group (12.8%); both were significantly higher than those in the chronic respiratory diseases (CRDs) group (8.8%), the acute upper respiratory tract infections (AURTIs) group (6.6%), and the non-respiratory diseases (NRDs) group (4.8%). MP positivity rates in the ALRTIs, AURTIs, NRDs, and SRLT groups showed significant seasonal variation, peaking in winter, followed by spring; both seasons exhibited significantly higher positivity rates than summer and autumn. Monthly MP positivity rate peaked in January and February across all groups, after which it generally decreased with mild fluctuations, with the ALRTIs group consistently exhibiting the highest positivity rate. Among children with ALRTIs and AURTIs, MP positivity rates were significantly higher in school-aged, preschool, and adolescent children than in toddlers, infants, and newborns (p < 0.001). Multivariable logistic regression analysis revealed that MP positivity was independently associated with healthcare setting (inpatient vs. outpatient/emergency, OR: 1.24, 95% CI: 1.15-1.35), and PCR assay type (multiplex vs. singleplex, OR: 2.45, 95% CI: 2.25-2.67).

CONCLUSIONS

Among children in Chengdu in 2024, MP PCR positivity peaked in winter (January-February) and was highest in school-aged children. These single-year findings may help inform local surveillance and guide future long-term epidemiological monitoring.