Purpose
Community-acquired pneumonia (CAP) is one of the most frequently encountered infectious diseases worldwide. Few studies have explored the microbial composition of the lower respiratory tract (LRT) and host metabolites of CAP. We analyzed the microbial composition of the LRT and levels of host metabolites to explore new biomarkers for CAP.
Patients and Methods
Bronchoalveolar lavage fluid (BALF) was collected from 28 CAP patients and 20 healthy individuals. Following centrifugation, BALF pellets were used for amplicon sequencing of a variable region of the bacterial 16S rDNA gene to characterize the microbial composition. Non-targeted metabolomics was used to detect host’s metabolites in the supernatant.
Results
Compared with healthy individuals, the bacterial alpha diversity in the LRT of CAP patients was significantly lower in CAP patients (p<0.05). On the bacterial genus level, over 20 genera were detected with lower relative abundance (p<0.05), while the relative abundance of
Ruminiclostridium
-6 was significantly higher in CAP patients. The levels of the host metabolites dimethyldisulfide, choline, pyrimidine, oleic acid and N-acetyl-neuraminic acid were all increased in BALF of CAP patients (p<0.05), while concentrations of lysophosphatidylcholines (LPC (12:0/0:0)) and phosphatidic acid (PA (20:4/2:0)) were decreased (p<0.05). Furthermore, the relative abundance of
Parvimonas, Treponema
-2,
Moraxella, Aggregatibacter, Filifactor, Fusobacterium, Lautropia
and
Neisseria
negatively correlated with concentrations of oleic acid (p<0.05). A negative correlation between the relative abundance of
Treponema
-2,
Moraxella, Filifactor, Fusobacterium
and dimethyldisulfide concentrations was also observed (p<0.05). In contrast, the relative abundance of
Treponema
-2,
Moraxella, Filifactor
, and
Fusobacterium
was found to be positively associated with concentrations of LPC (12:0/0:0) and PA (20:4/2:0) (p<0.05).
Conclusion
The composition of the LRT microbiome differed between healthy individuals and CAP patients. We propose that some respiratory microbial components and host metabolites are potentially novel diagnostic markers of CAP.
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