Massive tNGS Study Maps Severe Pediatric Pneumonia Pathogens in China

Severe pneumonia remains the leading infectious cause of death among children under five years of age worldwide, yet the identity of the pathogens driving these life-threatening lung infections has often been obscured by the limits of conventional diagnostic testing. A new retrospective study from Shandong, China, has now mapped the etiological landscape of severe pediatric pneumonia with unprecedented resolution, analyzing bronchoalveolar lavage fluid from 1,552 hospitalized children using targeted next-generation sequencing, a rapid and cost-effective molecular tool increasingly deployed in clinical settings. The findings, published in BMC Infectious Diseases, reveal a pathogen spectrum dominated by Mycoplasma pneumoniae, high rates of viral co-detection, and a strikingly high prevalence of macrolide resistance that carries direct implications for antimicrobial stewardship.

The research team, led by Shuyun Wang and Lingdong Zhu at the Children’s Hospital Affiliated to Shandong University, conducted the study among children admitted with a diagnosis of severe pneumonia who underwent tNGS testing of bronchoalveolar lavage fluid between January and December 2024. The cohort had a median age of 6.92 years, with an interquartile range of 5.32 to 8.10 years, indicating that most participants were school-aged children rather than infants. Despite the severity of illness in this population, the overall cure and improvement rate reached 99.94 percent, a figure that underscores both the effectiveness of supportive and pathogen-adapted therapy and the clinical value of rapid molecular pathogen identification in guiding treatment decisions.

The most remarkable finding of the study is the overwhelming predominance of Mycoplasma pneumoniae, which was detected in 96.07 percent of patients and circulated year-round without distinct seasonal peaks. This atypical bacterium, which lacks a cell wall and therefore is inherently resistant to beta-lactam antibiotics such as penicillin, has long been recognized as a major cause of community-acquired pneumonia in school-aged children. However, its near-universal presence in severe pediatric pneumonia cases, as revealed by tNGS of lower respiratory tract specimens, suggests that the organism plays a far more central role in severe disease than previously appreciated. The year-round circulation pattern also challenges the assumption that Mycoplasma pneumoniae outbreaks occur only in cyclical epidemic waves separated by quiet intervals.

Co-detection of multiple pathogens occurred in 47.23 percent of patients, with the most frequent combinations involving Mycoplasma pneumoniae alongside respiratory viruses, accounting for 30.67 percent of the cohort. The single most common co-detection pair was Mycoplasma pneumoniae with rhinovirus, found in 19.59 percent of patients. This high rate of mixed infections raises important questions about the pathogenesis of severe pneumonia, since viral infection may damage the respiratory epithelium and facilitate bacterial invasion, or the two organisms may simply coexist without either driving disease severity. The tNGS approach, which quantifies pathogen reads per 100,000 sequenced reads, allowed the researchers to detect these co-infections that would have been missed by traditional culture or single-pathogen PCR panels.

Multivariable analysis, adjusting for potential confounders, confirmed that Mycoplasma pneumoniae detection was independently associated with several clinically significant outcomes. Children with Mycoplasma pneumoniae had higher odds of fever, with an adjusted odds ratio of 1.89, atelectasis, with an adjusted odds ratio of 3.71, and pleural effusion, with an adjusted odds ratio of 2.89. Atelectasis, the collapse of part or all of a lung, and pleural effusion, the accumulation of fluid around the lungs, are both markers of severe lower respiratory tract involvement. The consistent association between Mycoplasma pneumoniae detection and these structural complications, with P values below 0.001 when comparing the Mycoplasma-positive and Mycoplasma-negative groups, provides strong evidence that this organism drives the most damaging clinical manifestations of severe pediatric pneumonia.

Rural residence emerged as the strongest independent risk factor for respiratory failure, with an adjusted odds ratio of 3.51, indicating that children from rural areas were more than three times as likely to develop the most dangerous complication of severe pneumonia. This finding points to potential disparities in access to early medical care, vaccination coverage, or nutritional status that may compound the severity of respiratory infections in rural populations. The identification of rural residence as a modifiable risk factor carries significant public health implications, suggesting that targeted interventions in rural communities could reduce the burden of respiratory failure among children with severe pneumonia.

Age-specific analysis revealed distinct pathogen patterns across pediatric age groups. Viral and bacterial pathogens were more prevalent in younger children, while Mycoplasma pneumoniae dominated in school-aged groups, peaking at 98.77 percent among children aged 5 to 7 years. This age-dependent distribution aligns with the known immunology of Mycoplasma pneumoniae, which tends to affect school-aged children whose immune systems mount vigorous inflammatory responses to the organism. In contrast, infants and toddlers are more susceptible to respiratory syncytial virus, parainfluenza virus, and encapsulated bacteria such as Streptococcus pneumoniae. The seasonal analysis showed that while Mycoplasma pneumoniae persisted year-round, other pathogens including rhinovirus, Streptococcus pneumoniae, and human parainfluenza virus exhibited distinct seasonal peaks, providing clinicians with a temporal framework for anticipating which pathogens are most likely responsible for severe pneumonia at any given time of year.

Perhaps the most clinically consequential finding of the study is the extraordinarily high prevalence of macrolide-resistant Mycoplasma pneumoniae, detected in 89.94 percent of the 1,491 patients with Mycoplasma pneumoniae infection. Macrolides, including azithromycin and erythromycin, are the first-line treatment for Mycoplasma pneumoniae infection in children, since beta-lactam antibiotics are ineffective against this cell wall-deficient organism. The resistance was predominantly driven by the A2063G mutation in the 23S ribosomal RNA gene, with two rare A2064G cases also identified. These mutations alter the macrolide binding site on the bacterial ribosome, rendering the antibiotics unable to inhibit protein synthesis. The near-universal macrolide resistance in this cohort means that standard first-line therapy is likely to fail in the vast majority of severe Mycoplasma pneumoniae cases, forcing clinicians to consider alternative agents such as tetracyclines or fluoroquinolones, which carry their own limitations in pediatric populations.

The study demonstrates the clinical utility of targeted next-generation sequencing in guiding resistance-adapted therapy and antimicrobial stewardship. By rapidly identifying both the causative pathogens and their resistance mutations directly from bronchoalveolar lavage fluid, tNGS enables clinicians to tailor antibiotic choices to the specific resistance profile of each patient’s infection, rather than relying on empirical therapy that may be rendered ineffective by the high prevalence of macrolide resistance. The technology also detects co-infections that would be missed by conventional methods, allowing for comprehensive pathogen coverage in mixed infections. As tNGS becomes more widely available, the findings from this large Shandong cohort provide a template for how molecular diagnostics can transform the management of severe pediatric pneumonia, moving the field toward precision medicine approaches that account for the local pathogen spectrum, resistance patterns, and clinical characteristics of the populations they serve.

Subject of Research: Etiological and clinical characteristics of severe pediatric pneumonia: a large retrospective tNGS cohort study using bronchoalveolar lavage fluid in Shandong, China

Article Title: Etiological and clinical characteristics of severe pediatric pneumonia: a large retrospective tNGS cohort study using bronchoalveolar lavage fluid in Shandong, China

Article References: Wang, S., Lv, X., Ma, Y., Hou, P., Zeng, Q., Wu, D., Wang, J., Yue, Y., Wang, Q., Guo, K., & Zhu, L. (2026). Etiological and clinical characteristics of severe pediatric pneumonia: a large retrospective tNGS cohort study using bronchoalveolar lavage fluid in Shandong, China. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14458-1

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14458-1

Keywords: Etiological, clinical, characteristics, severe, pediatric, pneumonia, large, retrospective, tNGS, cohort, bronchoalveolar, lavage