Species turnover within cystic fibrosis lung microbiota is indicative of acute pulmonary exacerbation onset.

Background: Acute pulmonary exacerbations (PEx) are associated with increased morbidity and earlier mortality for people living with cystic fibrosis (pwCF). The most common causes of PEx in CF are by bacterial infection and concomitant inflammation leading to progressive airway damage. To draw attention to the seriousness of PEx they have been labelled as 'lung attacks', much like a 'heart attack' for acute myocardial infarction. Treatment typically starts when a pwCF presents with worsening respiratory symptoms. Hence, there is a pressing need to identify indicative biomarkers of PEx onset to allow more timely intervention. Set within an ecological framework, we investigated temporal microbiota dynamics to connect changes in the lung microbiota of pwCF to changes in disease states across a PEx event.

Results: Species-time relationships (STR) describe how the richness of a community changes with time, here STRs were used to assess temporal turnover (w) within the lung microbiota of each pwCF (n = 12, mean sample duration 315.9 ± 42.7 days). STRs were characterised by high interpatient variability, indicating that turnover and hence temporal organization are a personalized feature of the CF lung microbiota. Greater turnover was found to be significantly associated with greater change in lung function with time. When microbiota turnover was examined at a finer scale across each pwCF time series, w-values could clearly be observed to increase in the exacerbation period, then peaking within the treatment period, demonstrating that increases in turnover were not solely a result of perturbations caused by PEx antibiotic interventions. STR w-values have been found to have a remarkable degree of similarity for different organisms, in a variety of habitats and ecosystems, and time lengths (typically not exceeding w = 0.5). Here, we found w-values soon increased beyond that. It was therefore possible to use the departure from that expected norm up to start of treatment to approximate onset of PEx in days (21.2 ± 8.9 days across the study participants).

Conclusions: Here, we illustrate that changes in turnover of the lung microbiota of pwCF can be indicative of PEx onset in considerable advance of when treatment would normally be initiated. This offers translational potential to enable early detection of PEx and consequent timely intervention. Video Abstract.