Clinical characteristics, risk factors, and pathogen spectrum of mixed infections in children with Mycoplasma pneumoniae pneumonia: a retrospective cohort study of 1,428 cases from a children’s medical centre in East China

ABSTRACT This study aimed to investigate the clinical characteristics, risk factors, and pathogen spectrum of mixed infections in children with Mycoplasma pneumoniae pneumonia (MPP). A total of 1,428 pediatric MPP patients were retrospectively included and categorized into a single infection group ( n = 528) and a mixed infection group ( n = 900), with the latter further divided into bacterial, bacterial–viral, and viral mixed infection subgroups. The results revealed that the children in the mixed infection group were younger (median 3–6 years vs 8 years, P < 0.001) and had shorter hospital stays (8 days vs 9 days, P < 0.001) but had a higher incidence of severe pneumonia (30.44% vs 20.27%, P < 0.001). Mixed infections occurred more frequently in autumn and presented with more prominent upper respiratory symptoms. Significant differences in the levels of some immune, coagulation, and inflammatory markers were detected between the two groups ( P < 0.05). The mixed infection group had higher rates of gastrointestinal dysfunction and myocardial injury. Multivariate regression analysis revealed longer cough duration, younger age, autumn onset, rhinorrhea, decreased complement C4 levels, and elevated antithrombin III (AT-III) levels as independent risk factors for mixed infection. Pathogen spectrum analysis revealed that Human rhinovirus and Streptococcus pneumoniae were the predominant viral and bacterial pathogens, respectively, in mixed infections. Mixed infections accounted for a substantial proportion of the MPP cases (63.03%) and were associated with a higher risk of severe disease. It is recommended that active pathogen testing be conducted in children with MPP and that a prediction model incorporating age, season, symptoms, and laboratory indicators be developed for early identification and precise intervention. IMPORTANCE This study highlights the importance of mixed infections in pediatric MPP patients. The results indicate that mixed infections account for up to 63.03% of MPP cases in children and are significantly associated with an increased risk of severe pneumonia. The key risk factors identified include younger age, autumn onset, rhinorrhea, decreased complement C4 levels, and elevated AT-III levels, providing a basis for the early identification of high-risk patients. Pathogen spectrum analysis identified human rhinovirus and Streptococcus pneumoniae as the predominant mixed infecting pathogens. These findings suggest that multipathogen testing should be implemented for children with MPP. This research supports the development of a risk prediction model to enable early warning and targeted intervention, thereby optimizing treatment, improving prognosis, and enhancing public health prevention and control strategies.