Clinical significance of cytomegalovirus detection in young children with Mycoplasma pneumoniae-associated community-acquired pneumonia: A retrospective cohort study

Background Mycoplasma pneumoniae ( M. pneumoniae )-associated community-acquired pneumonia (CAP) is common in children. Cytomegalovirus (CMV) is frequently detected in respiratory samples in this patient population. We aimed to explore the clinical implications of positive CMV DNA in bronchoalveolar lavage fluid (BALF) from immunocompetent children with M. pneumoniae -associated CAP. Methods A retrospective cohort study was conducted for M. pneumoniae -associated CAP children under two years old with CMV DNA test in BALF between January 1, 2022 and September 30, 2025. These children were assigned to the BALF CMV DNA positive group or negative group. Then, the inter-group characteristics were compared. Results Among the 66 children, 28 and 38 children were in the CMV DNA positive and negative groups, respectively. Children in the BALF CMV DNA positive group were more likely to experience duration of fever ≥ 3 days, had higher C-reactive protein and lactate dehydrogenase levels, showed a higher incidence of pulmonary consolidations, and required longer hospital stays. However, these children had a lower incidence of wheezing, when compared to children in the BALF CMV DNA negative group. Furthermore, virus co-infection was common in the BALF CMV DNA negative group, when compared to the BALF CMV DNA positive group (60.5% vs. 35.7%, p  = 0.046). All children fully recovered after intravenous azithromycin administration. Conclusions Both BALF CMV DNA positive and negative children with M. pneumoniae -associated CAP can reach full recovery after azithromycin treatment. However, the former group had stronger inflammations and required longer hospital stays, while the latter group were more likely to have virus co-infection. Clinical trial number: Not applicable.