Discussion
respiratory infections, pneumonia, critically ill, lung injury, non-VAP, VAP, traumatic, TBI, dysbiosis, pulmonary infections, sepsis, pulmonary disease
RESPIRATORY INFECTIONS, PNEUMONIA, CRITICALLY ILL, CRITICAL ILLNESS, PULMONARY INFECTIONS, ACUTE RESPIRATORY FAILURE, SEPSIS, PULMONARY DISEASE, PATHOGENESIS
The core finding of this study on lung microbiota in mechanically ventilated traumatic brain injured patients is:Specialized nutrition did not display a significant role in preventing VAP and was associated with no significant differences in microbiota composition.The analysis of BAL microbiota on patients who developed VAP post-ICU admission showed that at T0 and T7 there were different composition of BAL microbiota in terms of beta diversity. The microorganisms driving difference were It is important to remember that lung microbial community is dynamically renewed and replaced in healthy people, and the majority of microbes involved in these processes belong to four phyla: Among the most abundant Genera, we confirmed Our data showed a higher abundance of members of the Enterobacteriaceae Family, including Escherichia/Shigella, in the specialized nutrition group at T7, while in the standard nutrition group we found higher abundance of Staphylococcus at T7. These results might provide indirect support that different diets, particularly specialized nutrition, may play a role in gut-lung translocation of bacteria thus contributing to the pathogenesis of lung injury in critically ill patients.Among factors impacting on commensal bacteria growth and survival, nutrients availability and abundance and activation state of host immune cells are involved [To our knowledge, our study is the first to show that variation in beta diversity of lung microbiota is correlated to respiratory infections in TBI patients in ICU. This key result is compatible with findings in non-ICU lung microbiota where dysbiosis is a risk factor for several pulmonary disease [During the first week, no patient developed VAP. These data could be explained by the increased clinician’s attention to the employment of effective prevention strategies discussed in the previous narrative review by our group [In our study, a late tracheostomy was performed. Tracheostomy bypasses normal respiratory defense mechanisms, such as oropharynx and cilia, which contribute to the occurrence of VAP. However, the evidence on the advantages of early over late tracheostomy as risk factor for VAP is still debated [Based on the evidence that a group of patients developed VAP during their hospitalization, we retrospectively carried out the alpha and beta diversity analysis on the BAL samples at T0 and T7 in VAP vs no VAP groups. Data on mechanically ventilated critically ill patients with VAP and sepsis demonstrated that reduced microbial diversity in lower respiratory tract reflects high illness severity and are associated with mortality [Interestingly, although we did not observe differences in alpha diversity between the VAP and non-VAP patients, we found significant differences in beta diversity either at admission and seven days after ICU admission between the two groups, suggesting that different structures of BAL microbiota might be able to induce pulmonary infections during hospitalization. These results are consistent with recent studies highlighting the role of the commensal microbes of the respiratory tract in the development of pneumonia [Our data showed that Indeed, these authors found an increased relative abundance of the A limit of our study, besides the small sample size, is that the microbiota analysis was designed only for the first week in ICU. A future study will include samples collection over the first seven days to evaluate the longitudinal microbiota taxonomic profile.
However, the link between changes in the lung microbiota structure and subsequent occurrence of VAP highlights the importance of studying lung microbiota at the ICU admission. The lung microbiota is an understudied source of clinical variation in critical illness and represents a novel therapeutic target for the prevention and treatment of acute respiratory failure.