Comparison of severe and general Mycoplasma pneumoniae pneumonia in children: a targeted next-generation sequencing based study

The incidence and severity of Mycoplasma pneumoniae pneumonia (MPP) in children have increased after the pandemic of COVID-19, raising public concern. However, factors that affect the severity of MPP have not been well described. This study aimed to investigate the influence of Mycoplasma pneumoniae characters, respiratory co-existing pathogens, and host response on the severity of MPP. Clinical characteristics of 288 children hospitalized for MPP between November 2023 and July 2024 were analyzed retrospectively. Patients were divided into severe MPP (SMPP) and general MPP (GMPP) groups according to disease severity. Targeted next-generation sequencing (tNGS) was employed to analyze the respiratory pathogens of patients. Of 288 cases, there were 113 SMPP and 175 GMPP. Compared with GMPP group, children with SMPP had significantly higher levels of neutrophil percentage, Neutrophil to Lymphocyte Ratio (NLR), C-Reactive Protein (CRP), Alanine aminotransferase (ALT), Lactic dehydrogenase (LDH) and D-D dimer (all P < 0.05), which reflected a higher host immune response in SMPP group. Meanwhile, tNGS based pathogen analysis showed that Mycoplasma pneumoniae characters (A2063G mutation or not, pathogen concentration) were not associated with the severity of MPP (P > 0.05). Furthermore, co-existing pathogens analysis showed that the SMPP group had a lower number of co-detected pathogens, children with human respiratory syncytial virus (RSV) co-existing were more frequent in the SMPP group (all P < 0.05). Multivariate analysis showed that lower number of co-detected pathogens (decreased microbial diversity), RSV co-existing, elevated CRP, and LDH were independent risk factors for SMPP. Collectively, our data showed that respiratory microbiome and host response may play important roles in the pathology of MPP, decreased microbial diversity, RSV co-existing, CRP, and LDH level can predict the severity of MPP.