Abstract:

Objective To investigae microbial community structure of lower respiratory tract in severe hospital-acquired pneumonia (SHAP) patients in intensive care unit (ICU) using metagenomic next-generation sequencing (mNGS). Methods mNGS was performed on bronchoalveolar lavage fluid (BALF) of 84 patients with SHAP. Patients were grouped based on age, smoking status, underlying diseases and duration of artificial airway. The differences in α diversity, β diversity, microbial composition and community structure of airway microbiota were compared between different groups. The differential airway microbiota associated with artificial airway were screened, and microbial co-occurrence networks was constructed to observe the interaction in microorganisms. Results Results of α diversity analysis revealed that diversity and evenness of the microbial community were higher in young adults compared to those of middle-aged patients, while microbial diversity and evenness were significantly reduced in patients with comorbid stroke. In the group of artificial airway treatment, the diversity and uniformity of microorganisms decreased as the duration of artificial airway treatment increased. The diversity was the lowest when the artificial airway treatment lasted for more than 3 days. β diversity analysis confirmed that there were significant differences in the distinct microbial community structures between the >3 days support group and the non-intubated and ≤3 days support cohorts. Acinetobacter baumannii was dominant in all groups. The bacterial diversity was significantly higher in the middle-aged group, the non-smoking group, the group without artificial airway therapy, the group without diabetes mellitus, the group with artificial airway therapy ≥3 days and the group with chronic lung disease than those of other groups. In particular, pseudomonas aeruginosa, corynebacterium striatum and veillonella parvula were enriched in these groups. Difference analysis showed that there were significant differences in pseudomonas aeruginosa and corynebacterium striatum between the group with artificial airway treatment > 3 days, the group without artificial airway therapy and the group with artificial airway treatment ≤3 days. Network co-occurrence showed that there may be synergistic or antagonistic relationships between some microorganisms. Conclusion The microbial diversity of the lower respiratory tract in patients with SHAP significantly decreases in the elderly, those with concurrent stroke and those receiving artificial airway treatment. For these groups, rational use of antibiotics should be adopted to guide precise anti-infection treatment.

Key words: pneumonia, bronchoalveolar lavage fluid, microorganism, metagenomic next-generation sequencing