Respiratory microbiome in mechanically ventilated patients: a narrative review

Abstract

The respiratory microbiome has been less explored than the gut microbiome. Despite the speculated importance of dysbiosis of the microbiome in ventilator-associated pneumonia (VAP) and acute respiratory distress syndrome (ARDS), only few studies have been performed in invasively ventilated ICU patients. And only the results of small cohorts have been published. An overlap exists between bacterial populations observed in the lower respiratory tract and the oropharyngeal tract. The bacterial microbiota is characterized by relatively abundant bacteria difficult to cultivate by standard methods. Under mechanical ventilation, a dysbiosis occurs with a drop overtime in diversity. During VAP development, lung dysbiosis is characterized by a shift towards a dominant bacterial pathogen (mostly Proteobacteria) whereas enrichment of gut-associated bacteria mainly Enterobacteriaceae is the specific feature discriminating ARDS patients. However, the role of this dysbiosis in VAP and ARDS pathogenesis is not yet fully understood. A more in-depth analysis of the interplay between bacteria, virus and fungi and a better understanding of the hostmicrobiome interaction could provide a more comprehensive view of the role of the microbiome in VAP and ARDS pathogenesis. Priority should be given to validate a consensual and robust methodology for respiratory microbiome research and to conduct longitudinal studies. A deeper understanding of microbial interplay should be a valuable guide for care of ARDS and VAP preventive/therapeutic strategies. We present a review on the current knowledge and expose perspectives and potential clinical applications of respiratory microbiome research in mechanically ventilated patients.

Dysbiosis and structural disruption of the respiratory microbiota in COVID-19 patients with severe and fatal outcomes

“…Although the association of these factors with specific microbial groups in the respiratory tract has not been previously reported, the findings in this study open the path to further study the relationship between respiratory microbiota and clinical outcomes. The identification of pathogenic bacteria such as g_ Actinomyces g_ Prevotella and g_ Corynebacteriu m in association with two or more clinical factors further supports the current research line trying to correlate the gut-lung axis with pulmonary disease 32 .…”

Prophylactic application of antibiotics selects extended‐spectrum β‐lactamase and carbapenemases producing Gram‐negative bacteria in the oral cavity

“…However, introduction of new molecular techniques identified high diversity of microbial populations, including Prevotella spp, Streptococcus spp and Veilonella spp in the lungs of healthy persons, which are now considered as respiratory microbiota and are biomarkers of respiratory health (Fromentin et al . 2021). Mechanical ventilation and stay in ICU was found to be associated with the loss of microbial diversity and shift to predominance of one species, particularly P. aeruginosa and enrichment with gut microbiota.…”

“…This alteration in respiratory microbiota in ventilated patients was not linked to antibiotic usage (Fromentin et al . 2021). Previous studies found that change of respiratory microbiome affected the emergence of acute respiratory distress syndrome (ARDS) and systemic inflammatory response.…”

New insights into pneumonia in patients on prolonged mechanical ventilation: need for a new paradigm addressing dysbiosis

“…Uma melhor compreensão da microbiota utilizando metagenômica é necessária para melhorar o tratamento e para a efetiva prevenção da PAVM. (6) O microbioma tem um papel crítico na ativação imunológica e na defesa do hospedeiro em pacientes em VM prolongada.…”

“…A better understanding of the microbiota using metagenomics is required in order to improve treatment and for effective prevention of VAP. 6 The microbiome has a critical role in immune activation and host defense in patients on prolonged MV.…”