The microbiome in mechanically ventilated patients

Purpose of review Discovery of a normal lung microbiome requires reassessment of our concepts of HAP/VAP pathogenesis and has important implications for clinical diagnosis and management. Recent findings Changes in the microbiome of dental plaque are associated with increased risk of HAP/VAP. A transition to a lung microbiome enriched with gut flora is found in ARDS with an increased inflammatory response in patients with this change in microbial flora. A characteristic microbiome pattern of higher amounts of bacterial DNA, lower community diversity, and greater relative abundance of a single species characterize pneumonia and occasionally identify bacteria not found in culture. The influence of the microbiome makes probiotics a logical strategy to prevent or ameliorate HAP/VAP but so far clinical support is unclear. Summary The presence of a normal lung microbiome and the interaction of that microbiome with other microbiota have an important but previously overlooked impact on the pathogenesis of HAP/VAP. Deep sequencing suggests that the repertoire of microorganisms and the pattern of bacterial communities associated with HAP/VAP remains incompletely understood but recent studies are adding greater clarity.