Temporal dynamics of the oral microbiome after oral care in ventilated ICU patients and associations with outcomes: an exploratory 16S rRNA sequencing study

Abstract Objectives To evaluate oral microbiome alterations in ventilator-associated pneumonia (VAP) patients compared to healthy controls, and explore correlations between dynamic microbiome changes after oral care and clinical outcomes. Methods Fourteen VAP patients and seven healthy controls were enrolled. Oral samples were collected and analyzed using 16S rRNA gene sequencing. Eight VAP patients underwent serial oral swab sampling every 4 hours within 24 hours after oral care. Results VAP patients showed significantly reduced microbial diversity, with lower abundance of oral commensals such as Streptococcus , Neisseria , Prevotella and with higher abundance of Klebsiella and Acinetobacter , aligning with sputum culture findings. After oral care, microbiota diversity transiently increased at 0–4 hours, then declined. Dynamic changes of oral microbiota related to VAP outcomes. fatal cases displayed severe microbial dysbiosis, dominated by pulmonary pathogens. Conclusions Oral microbiota diversity in VAP patients is markedly reduced, with dynamic fluctuations after oral care. Microbial diversity is associated with clinical outcomes, highlighting the role of oral microbiota dysbiosis in VAP pathogenesis. Implications for Clinical Practice Oral microbiota composition and dynamics is related to VAP. Monitoring oral microbiota may help predict VAP risk and prognosis. Standardized oral care procedure may stabilize microbial composition, reduce pathogen overgrowth, and support improved outcomes in ventilated patients.