Oral microbiota dysbiosis contributes to occurrence of pneumonia in patients admitted to intensive care unit with spontaneous intracerebral hemorrhage.

Post-stroke pneumonia (PSP) is a major contributor to the high mortality rate among patients with spontaneous intracerebral hemorrhage. Dysbiosis of oral microbiota contributes to various pulmonary diseases through the oral-lung axis. This study aimed to explore the association between PSP and microbiota dysbiosis and to construct an early prediction model for PSP. A total of 139 patients admitted to the emergency intensive care unit between October 2022 and April 2024 were enrolled; 82 developed PSP. Oral microecological characteristics were analyzed to establish a PSP prediction model incorporating clinical characteristics. The relative abundance of oral microbiome was higher in patients with PSP according to abundance-based coverage estimator (z = -2.08, P = 0.03707) and Chao index (z = -2.09, P = 0.03673). A predictive model for PSP was built based on eight microbiomes and four clinical characteristics with an area under the curve of 0.837 (confidence interval: 0.757-0.917). The model was verified with area under the curve of 0.786 (95 % confidence interval: 0.643-0.929). Porphyromonas were the oral bacteria with the greatest difference in relative abundance between the two groups, and were therefore selected as the exposed bacterial species. Sprague-Dawley rats exposed to Porphyromonas gingivalis exhibited oral microbiota dysbiosis and developed pneumonia, which could be eliminated by metronidazole, confirming its causative role. In conclusion, oral microbiota dysbiosis contributes to PSP occurrence, representing a novel pathogenic mechanism that has promoted the establishment of an early prediction model for PSP, facilitated early diagnosis, and provided new insights into preventing PSP.