Bronchoalveolar lavage fluid microbiota dysbiosis in infants with protracted bacterial bronchitis.

Background: Protracted bacterial bronchitis (PBB) is a chronic purulent bronchitis which could cause recurrent coughing and wheezing in infants. Based on previous reports, main pathogens which caused PBB were identified in the patients, but their impacts on lung microbiota dysbiosis remain unclear.

Methods: In this study, bronchoalveolar lavage fluid (BALF) was collected from PBB infants and tracheomalacia (TM) infants younger than 3 years old under the instruction of Shenzhen Children's Hospital, and 12 samples were randomly selected for 16S rDNA analysis in each group. Based on the results of bacterial composition, the microbiota diversity and co-occurrence network in PBB and TM group were detected and compared.

Results: Microbiota diversity was significantly lower in PBB group than it in TM group (P<0.001 for the comparison of Shannon and Simpson indexes). The PBB group was found to harbor 25 accumulated bacterial agents by comparison with TM group, including Haemophilus (P<0.001) and Bacteroides (P<0.001). Whilst, the populations of Lactococcus (P<0.001) and Lactobacillus (P<0.001) were dramatically smaller in PBB group. The co-occurrence network in PBB group also differed from that of TM group. It contained four core nodes in PBB patients, including Haemophilus , Parabacteroides , Porphyromonas , and Cronobacter . Haemophilus was found to be negatively associated with most counterparts, including Clostridium and Bacillus .

Conclusions: PBB infants contained discrepant lung genera and co-occurrence network when compared with TM infants. This retrospective study may deepen our understanding of PBB pathogenesis, and it also provided a foundation for bacterial adjunctive therapy of infantile PBB in accordance with clinical treatment.