BACKGROUND: Knowledge on the etiology of LRTIs is essential for improvement of the clinical diagnosis and accurate treatment . Molecular detection methods were applied to identify a broad range of bacterial and viral pathogens in a large set of bronchial alveolar lavage (BAL) fluid samples . The patterns of detected pathogens were correlated to the clinical symptoms .

METHODS: BAL fluid samples and clinical data were collected from 573 hospitalized children between 1 month and 14 years of age with LRTIs, enrolled from January to December 2018 . Pathogens were detected using standardized clinical diagnostics, with a sensitive, high-throughput GeXP-based multiplex PCR and with multiplex qPCR . Data were analyzed to describe the correlation between the severity of respiratory tract disease and the pathogens identified .

RESULTS: The pathogen detection rate with GeXP-based PCR and multiplex qPCR was significantly higher than by clinical routine diagnostics (76.09% VS 36.13%, χ 2 = 8.191, P = 0.004). The most frequently detected pathogens in the BAL fluid were human adenovirus (HADV) (21.82 %), Mycoplasma pneumoniae (20.24 %), human rhinovirus (13.96 %), Streptococcus pneumoniae (8.90 %) and Haemophilus influenzae (8.90 %). In 16.4% of the cases co-detection with two or three different pathogens was found . Viral detection rates declined with age, while atypical pathogen detection rates increased with age . Oxygen supply in the HADV and Influenza H1N1 infected patients was more frequent (49.43 %) than in patients infected with other pathogens .

CONCLUSION: Broad range detection of viral and bacterial pathogens using molecular methods is a promising and implementable approach to improve clinical diagnosis and accurate treatment of LRTI in children.